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2025,37(6):1871-1882, DOI: 10.18307/2025.0601
Abstract:
Inland waters are an important natural source of methane to the atmosphere, a potent greenhouse gas. The potential of sediment methane production (PMP) under anaerobic conditions is a key indicator for the level of atmospheric emissions of methane. However, there is a lack of cross-system studies on the sediment PMP in inland waters， the underlying driving mechanisms are still unclear. In this study, we collected data on PMP in inland waters in China including reservoirs, lakes, rivers and wetlands. Combined with some unpublished data (a total of 210 data points), the temporal and spatial distribution of sediment PMP in several different systems was explored, and the drivers of the sediment PMP were identified. We found that PMP was seasonally variable, showing a trend of being significantly greater in the rainy season than in the dry season (about 3.5 times); damming caused a significant increase in PMP by more than ten times, and sediment PMP in reservoirs and lakes was significantly greater than that of rivers or wetlands. Correlation analysis showed that eutrophication caused by human activities had a significant driving effect on sediment PMP. Water temperature, water depth and sediment organic matter content had a significant positive stimulating effect on sediment PMP, while salinity had a significant inhibitory effect. In the context of global climate change, in order to make good future projections of carbon emissions from inland waters, human disturbances such as damming and eutrophication must be well incorporated, in addition to the natural process of global warming.
Inland waters are an important natural source of methane to the atmosphere, a potent greenhouse gas. The potential of sediment methane production (PMP) under anaerobic conditions is a key indicator for the level of atmospheric emissions of methane. However, there is a lack of cross-system studies on the sediment PMP in inland waters， the underlying driving mechanisms are still unclear. In this study, we collected data on PMP in inland waters in China including reservoirs, lakes, rivers and wetlands. Combined with some unpublished data (a total of 210 data points), the temporal and spatial distribution of sediment PMP in several different systems was explored, and the drivers of the sediment PMP were identified. We found that PMP was seasonally variable, showing a trend of being significantly greater in the rainy season than in the dry season (about 3.5 times); damming caused a significant increase in PMP by more than ten times, and sediment PMP in reservoirs and lakes was significantly greater than that of rivers or wetlands. Correlation analysis showed that eutrophication caused by human activities had a significant driving effect on sediment PMP. Water temperature, water depth and sediment organic matter content had a significant positive stimulating effect on sediment PMP, while salinity had a significant inhibitory effect. In the context of global climate change, in order to make good future projections of carbon emissions from inland waters, human disturbances such as damming and eutrophication must be well incorporated, in addition to the natural process of global warming.
Li Minne, Wang Yan, Bao Chunpeng, Guo Zhijie, Xu Xu, Chen Xiaolong, Ke Senfan, Lin Chenyu, Tan Junjun, Shi Xiaotao
2025,37(6):1883-1896, DOI: 10.18307/2025.0602
Abstract:
With the intensification of anthropogenic disturbances, such as water resource development, water pollution, and overfishing, fish diversity and population abundance have significantly declined, posing a severe threat to aquatic ecosystems. Systematic monitoring of fish movement behavior and physiological responses to environmental changes, along with the scientific analysis of the relationship between behavioral responses and environmental factors, is critical for designing habitat conditions centered on the ecological needs of fish species. This is essential for advancing fish conservation research. The development of acoustic and electronic tagging systems has provided a robust scientific tool for fish conservation studies. These tags, with diverse functionalities, can be implanted in fish bodies or attached externally to enable systematic monitoring of fish movement behavior and habitat information. This paper provides a comprehensive review of the acoustic and electronic tags commonly used in fish conservation research, classifying them into four categories based on their functions: short-range coded identification and counting tags, spatial tracking and positioning tags, physiological state monitoring tags, and environmental data logging tags. First, the fundamental features and technical principles of these tags are introduced. Then, the applications and research progress of each tag type are discussed in detail, focusing on areas such as fish passage efficiency monitoring, fish movement tracking, physiological state assessment, and habitat information evaluation. Finally, the existing challenges and future development directions of acoustic and electronic tagging technologies in fish conservation are highlighted based on the current state of applications. This study aims to systematically summarize the application status and developmental trends of acoustic and electronic tagging technologies in fish conservation research, providing scientific and technical guidance for aquatic ecosystem protection.
With the intensification of anthropogenic disturbances, such as water resource development, water pollution, and overfishing, fish diversity and population abundance have significantly declined, posing a severe threat to aquatic ecosystems. Systematic monitoring of fish movement behavior and physiological responses to environmental changes, along with the scientific analysis of the relationship between behavioral responses and environmental factors, is critical for designing habitat conditions centered on the ecological needs of fish species. This is essential for advancing fish conservation research. The development of acoustic and electronic tagging systems has provided a robust scientific tool for fish conservation studies. These tags, with diverse functionalities, can be implanted in fish bodies or attached externally to enable systematic monitoring of fish movement behavior and habitat information. This paper provides a comprehensive review of the acoustic and electronic tags commonly used in fish conservation research, classifying them into four categories based on their functions: short-range coded identification and counting tags, spatial tracking and positioning tags, physiological state monitoring tags, and environmental data logging tags. First, the fundamental features and technical principles of these tags are introduced. Then, the applications and research progress of each tag type are discussed in detail, focusing on areas such as fish passage efficiency monitoring, fish movement tracking, physiological state assessment, and habitat information evaluation. Finally, the existing challenges and future development directions of acoustic and electronic tagging technologies in fish conservation are highlighted based on the current state of applications. This study aims to systematically summarize the application status and developmental trends of acoustic and electronic tagging technologies in fish conservation research, providing scientific and technical guidance for aquatic ecosystem protection.
Bao Hangtong, Li Yiping, Zhao Guoli, Li Ronghui, Zhu Ya, Yu Min, Pan Haiping, Wang Yaning, Wang Can, Wang Chuer, Huang Xusheng
2025,37(6):1897-1909, DOI: 10.18307/2025.0611
Abstract:
Dawangtan Reservoir is a typical large drinking water source reservoir in the south subtropical region. Cyanobacterial dominance and algal blooms caused by eutrophication pose major threats to its water supply security. Understanding the characteristics of the phytoplankton community and the driving factors behind cyanobacterial dominance is of great significance for algal bloom prevention and the management of reservoir water supply safety. A quarterly investigation of the aquatic environment and phytoplankton community in the Dawanqtan Reservoir was conducted in 2021 to explore the seasonal dynamics of the phytoplankton community and the driving factors behind the dominance of filamentous cyanobacteria. The results indicated that the phytoplankton in Dawangtan Reservoir comprised 127 species from 7 phyla, with Chlorophyta, Bacillariophyta, and Cyanophyta being the dominant groups in terms of species composition, belonging to 26 functional groups. The phytoplankton cell density ranged from 1.2×106 to 430×106 cells/L, exhibiting the order of autumn ＞ spring ＞ winter ＞ summer, while the biomass ranged from 0.14 to 51 mg/L, with the order of autumn ＞ winter and spring ＞ summer. The dominant genera wereLimnothrix andPseudanabaena, and the functional group S1 was the long-term dominant functional group. The comprehensive trophic level index (TLI) of the reservoir ranged between 36.02 and 49.57, indicating a mesotrophic state. Mantel tests and redundancy analysis (RDA) revealed that water temperature, transparency, and nitrogen concentration were significant explanatory variables influencing the dominance of filamentous cyanobacteria. The absolute dominance of filamentous cyanobacteria occurred in Autumn, characterized by lower transparency and nitrogen concentration but higher water temperature, representing a high-risk period for blooms ofLimnothrix andPseudanabaena. Combined with functional group analysis, the results indicate that the turbid environment of large reservoirs is an important factor promoting the dominance of filamentous cyanobacteria. In Autumn, water temperature and nutrient conditions fall within the optimal range for the growth ofLimnothrix andPseudanabaena, serving as key drivers for their massive proliferation. Given the threat posed by filamentous cyanobacteria such asLimnothrix andPseudanabaena, attention should be paid to the causes of increased turbidity and water color in reservoirs to improve water transparency and thereby limit the formation of filamentous cyanobacterial dominance.
Dawangtan Reservoir is a typical large drinking water source reservoir in the south subtropical region. Cyanobacterial dominance and algal blooms caused by eutrophication pose major threats to its water supply security. Understanding the characteristics of the phytoplankton community and the driving factors behind cyanobacterial dominance is of great significance for algal bloom prevention and the management of reservoir water supply safety. A quarterly investigation of the aquatic environment and phytoplankton community in the Dawanqtan Reservoir was conducted in 2021 to explore the seasonal dynamics of the phytoplankton community and the driving factors behind the dominance of filamentous cyanobacteria. The results indicated that the phytoplankton in Dawangtan Reservoir comprised 127 species from 7 phyla, with Chlorophyta, Bacillariophyta, and Cyanophyta being the dominant groups in terms of species composition, belonging to 26 functional groups. The phytoplankton cell density ranged from 1.2×106 to 430×106 cells/L, exhibiting the order of autumn ＞ spring ＞ winter ＞ summer, while the biomass ranged from 0.14 to 51 mg/L, with the order of autumn ＞ winter and spring ＞ summer. The dominant genera wereLimnothrix andPseudanabaena, and the functional group S1 was the long-term dominant functional group. The comprehensive trophic level index (TLI) of the reservoir ranged between 36.02 and 49.57, indicating a mesotrophic state. Mantel tests and redundancy analysis (RDA) revealed that water temperature, transparency, and nitrogen concentration were significant explanatory variables influencing the dominance of filamentous cyanobacteria. The absolute dominance of filamentous cyanobacteria occurred in Autumn, characterized by lower transparency and nitrogen concentration but higher water temperature, representing a high-risk period for blooms ofLimnothrix andPseudanabaena. Combined with functional group analysis, the results indicate that the turbid environment of large reservoirs is an important factor promoting the dominance of filamentous cyanobacteria. In Autumn, water temperature and nutrient conditions fall within the optimal range for the growth ofLimnothrix andPseudanabaena, serving as key drivers for their massive proliferation. Given the threat posed by filamentous cyanobacteria such asLimnothrix andPseudanabaena, attention should be paid to the causes of increased turbidity and water color in reservoirs to improve water transparency and thereby limit the formation of filamentous cyanobacterial dominance.
2025,37(6):1910-1917, DOI: 10.18307/2025.0612
Abstract:
To quantitatively evaluate the concentration of algae-derived phosphorus in Lake Taihu and the influence of the algal community structure on it and to better understand the relationship between algal evolution and the internal phosphorus cycle of the lake, this study calculated the concentration of total algae-derived phosphorus in Lake Taihu and its proportion to total phosphorus in the lake based on the monitoring data and investigation data of algae and water quality of Lake Taihu from 2021 to 2023. The results showed that from 2021 to 2023, the total algal density of Lake Taihu decreased from 6.3 × 107 cells/L to 4.4 × 107 cells/L （annual average value）, the proportion ofMicrocystis decreased from 79.8% to 35.6%. On the other hand, the density and proportion of cryptophyta, chlorophyta and bacillariophyta increased significantly, and the whole lake's algal community changed significantly. During the same period, the total phosphorus concentration in the Lake Taihu fluctuated from 0.053 mg/L to 0.062 mg/L. The average proportion of particulate total phosphorus was 60.4%, of which the proportion of algae-derived phosphorus in particulate total phosphorus and total phosphorus was 49.4% and 29.6%, respectively, indicating that algae-derived phosphorus is an important component of particulate phosphorus. According to the further subdivision of the algal community structure, it is found that the algae-derived phosphorus in Lake Taihu is mainly contributed by three categories, including cyanophyta, bacillariophyta and chlorophyta. From 2021 to 2022, the contribution rates of cyanophyta to algae-derived phosphorus were 66.5% and 65.7%, respectively. With the rapid decrease in cyanophyta density in 2023, their contribution and proportion of algae-derived phosphorus also significantly decreased, while the contribution and proportion of algae-derived phosphorus from bacillariophyta increased from 23.9% to 56.1%. The total algae and cyanophyta density in 2023 had significantly decreased compared to 2021, but due to the increase in the proportion of bacillariophyta, chlorophyta and other categories, the increase in algae-derived phosphorus provided by them compensated for the decrease in cyanophyta algae-derived phosphorus, ultimately leading to an increase in the total algae-derived phosphorus in the entire lake instead of a decrease. Although the increase in algal density of bacillariophyta and other categories is not as significant as the decrease in cyanophyta density, they have larger cell volume and higher monomeric phosphorus content, thus exhibiting a more significant compensatory effect on algal-derived phosphorus.
To quantitatively evaluate the concentration of algae-derived phosphorus in Lake Taihu and the influence of the algal community structure on it and to better understand the relationship between algal evolution and the internal phosphorus cycle of the lake, this study calculated the concentration of total algae-derived phosphorus in Lake Taihu and its proportion to total phosphorus in the lake based on the monitoring data and investigation data of algae and water quality of Lake Taihu from 2021 to 2023. The results showed that from 2021 to 2023, the total algal density of Lake Taihu decreased from 6.3 × 107 cells/L to 4.4 × 107 cells/L （annual average value）, the proportion ofMicrocystis decreased from 79.8% to 35.6%. On the other hand, the density and proportion of cryptophyta, chlorophyta and bacillariophyta increased significantly, and the whole lake's algal community changed significantly. During the same period, the total phosphorus concentration in the Lake Taihu fluctuated from 0.053 mg/L to 0.062 mg/L. The average proportion of particulate total phosphorus was 60.4%, of which the proportion of algae-derived phosphorus in particulate total phosphorus and total phosphorus was 49.4% and 29.6%, respectively, indicating that algae-derived phosphorus is an important component of particulate phosphorus. According to the further subdivision of the algal community structure, it is found that the algae-derived phosphorus in Lake Taihu is mainly contributed by three categories, including cyanophyta, bacillariophyta and chlorophyta. From 2021 to 2022, the contribution rates of cyanophyta to algae-derived phosphorus were 66.5% and 65.7%, respectively. With the rapid decrease in cyanophyta density in 2023, their contribution and proportion of algae-derived phosphorus also significantly decreased, while the contribution and proportion of algae-derived phosphorus from bacillariophyta increased from 23.9% to 56.1%. The total algae and cyanophyta density in 2023 had significantly decreased compared to 2021, but due to the increase in the proportion of bacillariophyta, chlorophyta and other categories, the increase in algae-derived phosphorus provided by them compensated for the decrease in cyanophyta algae-derived phosphorus, ultimately leading to an increase in the total algae-derived phosphorus in the entire lake instead of a decrease. Although the increase in algal density of bacillariophyta and other categories is not as significant as the decrease in cyanophyta density, they have larger cell volume and higher monomeric phosphorus content, thus exhibiting a more significant compensatory effect on algal-derived phosphorus.
2025,37(6):1918-1925, DOI: 10.18307/2025.0613
Abstract:
Methylphosphonate (MPn), a typical organophosphonate characterized by a C—P bond, profoundly influences phosphorus cycling and methane (CH4) production mechanisms in aquatic ecosystems through its biosynthesis and degradation processes. However, there is limited research on the dynamics of MPn in water bodies and the MPn accumulation capacity of algae. This study employed liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (LC-MS/MS) to quantify MPn in 21 water samples and 15 algal species. Combined with field monitoring, algal laboratory cultivation, and raw water incubation experiments (including MPn/Pi addition, BES treatment, algal filtration, and dark treatment), the relationship between MPn dynamics and CH4 generation was investigated. The results revealed that MPn was detected in 52.4% (11/21) of water samples ((1.50±0.24)-(6.99±0.59) μg/L), and 93.3% (14/15) of algal strains accumulated intracellular MPn ((1.87±0.57)-(22.24±5.81) μg/L). Notably,Microcystis sp.FACHB-3602 exhibited dynamic MPn accumulation during 7 days of cultivation (peak value: （8.63±0.85） μg/L), indicating that algae are a significant biological source of MPn in aquatic ecosystems. In both water samples and algae, the contribution of MPn-P to dissolved organic phosphorus(0.70%-37.85%, 0.21%-0.90%) was significantly higher than that of MPn-C to dissolved organic carbon (0.00%-0.05%, 0.00%-0.01%), highlighting the dominant role of MPn in phosphorus cycling from an ecological stoichiometric perspective. Raw water incubation experiments demonstrated that MPn addition increased CH4 production by 157.43% compared to the control, while the simultaneous addition of inorganic phosphorus (Pi) suppressed CH4 generation. Algal filtration reduced CH4 roduction by 23.96%, whereas dark treatment promoted CH4 accumulation. These findings suggest that algal-bacterial interactions regulate MPn turnover and aerobic CH4 production, modulated by inorganic phosphorus availability. This study provides critical theoretical insights for further exploration of MPn's role in aquatic phosphorus cycling and aerobic CH4 production mechanisms.
Methylphosphonate (MPn), a typical organophosphonate characterized by a C—P bond, profoundly influences phosphorus cycling and methane (CH4) production mechanisms in aquatic ecosystems through its biosynthesis and degradation processes. However, there is limited research on the dynamics of MPn in water bodies and the MPn accumulation capacity of algae. This study employed liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (LC-MS/MS) to quantify MPn in 21 water samples and 15 algal species. Combined with field monitoring, algal laboratory cultivation, and raw water incubation experiments (including MPn/Pi addition, BES treatment, algal filtration, and dark treatment), the relationship between MPn dynamics and CH4 generation was investigated. The results revealed that MPn was detected in 52.4% (11/21) of water samples ((1.50±0.24)-(6.99±0.59) μg/L), and 93.3% (14/15) of algal strains accumulated intracellular MPn ((1.87±0.57)-(22.24±5.81) μg/L). Notably,Microcystis sp.FACHB-3602 exhibited dynamic MPn accumulation during 7 days of cultivation (peak value: （8.63±0.85） μg/L), indicating that algae are a significant biological source of MPn in aquatic ecosystems. In both water samples and algae, the contribution of MPn-P to dissolved organic phosphorus(0.70%-37.85%, 0.21%-0.90%) was significantly higher than that of MPn-C to dissolved organic carbon (0.00%-0.05%, 0.00%-0.01%), highlighting the dominant role of MPn in phosphorus cycling from an ecological stoichiometric perspective. Raw water incubation experiments demonstrated that MPn addition increased CH4 production by 157.43% compared to the control, while the simultaneous addition of inorganic phosphorus (Pi) suppressed CH4 generation. Algal filtration reduced CH4 roduction by 23.96%, whereas dark treatment promoted CH4 accumulation. These findings suggest that algal-bacterial interactions regulate MPn turnover and aerobic CH4 production, modulated by inorganic phosphorus availability. This study provides critical theoretical insights for further exploration of MPn's role in aquatic phosphorus cycling and aerobic CH4 production mechanisms.
Mo Luqing, Yang Yang, Tai Yiping, Dai Yunv, Tao Ran, Zhang Xiaomeng, Yu Bailun, Zhang Jie, Ou Tingzhe, Li Ming, Xuan Qianhong, Zhu Wenling, Zhou Xinmin, Huang Jiajun
2025,37(6):1926-1937, DOI: 10.18307/2025.0614
Abstract:
The study of attached algae communities' assembly mechanisms is essential for understanding the restoration of river ecosystem structure and function. This study analyzed attached algae communities in three representative rivers flowing through Guangzhou—Chebei River (natural habitat), Liede River (highly canalized), and Shahe River (mixed habitat)—that are subject to a low water level operation strategy. The analysis covered four consecutive flood seasons from 2020 to 2023, focusing on the recovery and environmental drivers of these communities under near-natural restoration measures. The results showed that 193 algal species across 6 phyla, 53 families, and 90 genera were recorded, with Bacillariophyta being dominant (51.26%). No significant spatial differences in algal standing stocks were found, while significant annual differences occurred, indicating higher temporal than spatial heterogeneity. Chebei River had the highest total number of species (184), while Liede River showed the highest abundance (2.17×109 cells/m2), biomass (3.16×103 mg/m2), Shannon diversity index (3.14), and Evenness index (0.66). Annually, Liede River had the largest increases in species and Shannon diversity index (41.43% and 15.58%, respectively), and Shahe River had the highest abundance and biomass increase (92.62% and 96.53%, respectively), with Evenness index remaining stable at around 0.6. These findings highlighted the effectiveness of near-natural restoration for attached algae recovery. Niche breadth and overlap analysis indicated that the attached algal communities in the studied rivers maintained overall stable niche breadth, with niche overlap between most species being below the competition threshold (0.6). These results reflect high resource-use efficiency, low interspecific competition pressure, and a relatively stable state of the community. The standardized random rate analysis revealed that either deterministic or stochastic processes could dominate the restoration process, and their relative contributions were regulated by environmental heterogeneity. Redundancy analysis further identified that total nitrogen, total phosphorus, dissolved oxygen, water depth and flow velocity are key factors affecting the rivers attached algae communities. The findings provide empirical support and a scientific basis for the effective implementation of near-natural restoration in urban river channels.
The study of attached algae communities' assembly mechanisms is essential for understanding the restoration of river ecosystem structure and function. This study analyzed attached algae communities in three representative rivers flowing through Guangzhou—Chebei River (natural habitat), Liede River (highly canalized), and Shahe River (mixed habitat)—that are subject to a low water level operation strategy. The analysis covered four consecutive flood seasons from 2020 to 2023, focusing on the recovery and environmental drivers of these communities under near-natural restoration measures. The results showed that 193 algal species across 6 phyla, 53 families, and 90 genera were recorded, with Bacillariophyta being dominant (51.26%). No significant spatial differences in algal standing stocks were found, while significant annual differences occurred, indicating higher temporal than spatial heterogeneity. Chebei River had the highest total number of species (184), while Liede River showed the highest abundance (2.17×109 cells/m2), biomass (3.16×103 mg/m2), Shannon diversity index (3.14), and Evenness index (0.66). Annually, Liede River had the largest increases in species and Shannon diversity index (41.43% and 15.58%, respectively), and Shahe River had the highest abundance and biomass increase (92.62% and 96.53%, respectively), with Evenness index remaining stable at around 0.6. These findings highlighted the effectiveness of near-natural restoration for attached algae recovery. Niche breadth and overlap analysis indicated that the attached algal communities in the studied rivers maintained overall stable niche breadth, with niche overlap between most species being below the competition threshold (0.6). These results reflect high resource-use efficiency, low interspecific competition pressure, and a relatively stable state of the community. The standardized random rate analysis revealed that either deterministic or stochastic processes could dominate the restoration process, and their relative contributions were regulated by environmental heterogeneity. Redundancy analysis further identified that total nitrogen, total phosphorus, dissolved oxygen, water depth and flow velocity are key factors affecting the rivers attached algae communities. The findings provide empirical support and a scientific basis for the effective implementation of near-natural restoration in urban river channels.
2025,37(6):1938-1947, DOI: 10.18307/2025.0615
Abstract:
Chlorophyll-a is an important indicator of primary productivity in lake ecosystems, and its concentration changes reflect the nutritional status and ecological health of lakes. Based on water quality and environmental data from Lake Chagannaoer between 2011 and 2024, this study used correlation and redundancy analysis to reveal the interannual and seasonal variation characteristics of chlorophyll-a concentration and its key driving factors. The results showed that between 2011 and 2024, the interannual variation of chlorophyll-a concentration in Lake Chagannaoer was stable, mainly regulated by hydrological conditions, nutrient inputs, and human activities. Seasonally, chlorophyll-a concentration follows the pattern of summer＞winter＞autumn＞spring. In spring, water dilution led to a decrease in chlorophyll-a concentration, while in summer, the rise in temperature promoted phytoplankton proliferation. Autumn cooling inhibited reproduction, and winter freezing led to the migration of nutrients into the water, with photosynthesis under the ice maintaining relatively high chlorophyll-a concentrations. The study further found that in spring and autumn, chlorophyll-a concentration was positively correlated with total nitrogen and negatively correlated with total phosphorus; whereas in summer and winter, chlorophyll-a concentration was negatively correlated with total nitrogen and positively correlated with total phosphorus, reflecting the seasonal impact of nutrient changes on phytoplankton growth. Redundancy analysis further indicated that the seasonal variation of chlorophyll-a concentration was influenced not only by the current season's climate and environmental factors but also by the interactions between consecutive seasons, creating cross-seasonal chain effects. Future research should focus on inter-seasonal relationships and environmental effects to further uncover the complexity of lake ecosystems, providing scientific evidence for lake management and conservation.
Chlorophyll-a is an important indicator of primary productivity in lake ecosystems, and its concentration changes reflect the nutritional status and ecological health of lakes. Based on water quality and environmental data from Lake Chagannaoer between 2011 and 2024, this study used correlation and redundancy analysis to reveal the interannual and seasonal variation characteristics of chlorophyll-a concentration and its key driving factors. The results showed that between 2011 and 2024, the interannual variation of chlorophyll-a concentration in Lake Chagannaoer was stable, mainly regulated by hydrological conditions, nutrient inputs, and human activities. Seasonally, chlorophyll-a concentration follows the pattern of summer＞winter＞autumn＞spring. In spring, water dilution led to a decrease in chlorophyll-a concentration, while in summer, the rise in temperature promoted phytoplankton proliferation. Autumn cooling inhibited reproduction, and winter freezing led to the migration of nutrients into the water, with photosynthesis under the ice maintaining relatively high chlorophyll-a concentrations. The study further found that in spring and autumn, chlorophyll-a concentration was positively correlated with total nitrogen and negatively correlated with total phosphorus; whereas in summer and winter, chlorophyll-a concentration was negatively correlated with total nitrogen and positively correlated with total phosphorus, reflecting the seasonal impact of nutrient changes on phytoplankton growth. Redundancy analysis further indicated that the seasonal variation of chlorophyll-a concentration was influenced not only by the current season's climate and environmental factors but also by the interactions between consecutive seasons, creating cross-seasonal chain effects. Future research should focus on inter-seasonal relationships and environmental effects to further uncover the complexity of lake ecosystems, providing scientific evidence for lake management and conservation.
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2026,(3):000-000, DOI: 10.18307/2026.0300
Available online: November 14, 2025
Abstract:
Algal blooms caused by phytoplankton overgrowth pose a common challenge for lake management worldwide. In China, current strategies primarily rely on environmental standards such as the “Environmental Quality Standards for Surface Water”, using total nitrogen and total phosphorus concentrations as key control targets. However, these efforts often yield limited success despite high investment. Notably, in many lakes, algal bloom intensity has increased even as nutrient concentrations stabilized or declined, highlighting a disconnect between static nutrient criteria and the dynamic growth responses of phytoplankton. The theory of limiting factors provides a scientific basis for building a precision control system. Based on Liebig’s law of the minimum and Blackman’s law of limiting factors, this review synthesizes multiple constraints on phytoplankton growth, including nutrients (e.g., nitrogen, phosphorus), trace elements, light, temperature, and ecological interactions such as grazing and macrophyte competition. We evaluate the strengths and limitations of four diagnostic approaches: experimental assays, empirical thresholds, residual analysis, and regression modeling. Three priority research directions are proposed: (1) clarifying the context-specific applicability of nitrogen reduction across lake types; (2) establishing a “climate potential–realized performance” framework for assessing nutrient assimilation efficiency; and (3) investigating how non-classical food web interactions influence bloom dynamics in shallow lakes. This study aims to support the transition from generalized nutrient control toward precision eco-management strategies for algal blooms in Chinese lakes.
Algal blooms caused by phytoplankton overgrowth pose a common challenge for lake management worldwide. In China, current strategies primarily rely on environmental standards such as the “Environmental Quality Standards for Surface Water”, using total nitrogen and total phosphorus concentrations as key control targets. However, these efforts often yield limited success despite high investment. Notably, in many lakes, algal bloom intensity has increased even as nutrient concentrations stabilized or declined, highlighting a disconnect between static nutrient criteria and the dynamic growth responses of phytoplankton. The theory of limiting factors provides a scientific basis for building a precision control system. Based on Liebig’s law of the minimum and Blackman’s law of limiting factors, this review synthesizes multiple constraints on phytoplankton growth, including nutrients (e.g., nitrogen, phosphorus), trace elements, light, temperature, and ecological interactions such as grazing and macrophyte competition. We evaluate the strengths and limitations of four diagnostic approaches: experimental assays, empirical thresholds, residual analysis, and regression modeling. Three priority research directions are proposed: (1) clarifying the context-specific applicability of nitrogen reduction across lake types; (2) establishing a “climate potential–realized performance” framework for assessing nutrient assimilation efficiency; and (3) investigating how non-classical food web interactions influence bloom dynamics in shallow lakes. This study aims to support the transition from generalized nutrient control toward precision eco-management strategies for algal blooms in Chinese lakes.
Wu Tongfei, Lu Taoxiu, Lyu Hongjian, Ding Yuwei, Yang Li, Tian Zhili, Xi Dan, Deng Huatang, Yao Weizhi, Fu Mei
2026,(3):000-000, DOI: 10.18307/2026.0332
Available online: November 12, 2025
Abstract:
The current study aims to investigate the reproductive status and adaptive strategies of Coilia nasus in the Three Gorges Reservoir Region (TGRR). A total of 388 specimens were collected from the Wushan to Fuling section, which is the core area of the TGRR, between June and August 2021 to 2023. The analysis revealed that the current age structure of the C. nasus population is stable, with a female-to-male sex ratio of 0.92:1 in the spawning population. The youngest sexually mature individuals were 1 year old for both sexes. The females’ biological minimum size was 152.5 mm in body length and 11.96 g in body weight, while the males’ was 166.6 mm and 17.64 g, respectively. The average absolute fecundity and relative fecundity of C. nasus were (3.10±2.16)×104 eggs and (605.42±181.85) eggs/g, respectively. The egg diameter was (615.47±107.30) μm on average, and exhibited a unimodal distribution, which indicated a single spawning type. The average gonadosomatic index (GSI) was (6.32±4.52)% for females and (3.74±1.63)% for males, while the average hepatosomatic index (HSI) was (1.15±1.10)% for females and (0.63±0.53)% for males, respectively. Compared with the studies on C. nasus in the TGRR and other Yangtze River waters prior, the current spawning population in the TGRR tends to be shifting towards characteristics of an r-strategist, which is reducing egg size and increasing absolute fecundity. In conclusion, the stable population structure and size of C. nasus suggest that it has fully adapted to the environment of the TGRR. Its distribution range is likely to expand further into other upstream waters of the Yangtze River, including both the mainstem and its tributaries.
The current study aims to investigate the reproductive status and adaptive strategies of Coilia nasus in the Three Gorges Reservoir Region (TGRR). A total of 388 specimens were collected from the Wushan to Fuling section, which is the core area of the TGRR, between June and August 2021 to 2023. The analysis revealed that the current age structure of the C. nasus population is stable, with a female-to-male sex ratio of 0.92:1 in the spawning population. The youngest sexually mature individuals were 1 year old for both sexes. The females’ biological minimum size was 152.5 mm in body length and 11.96 g in body weight, while the males’ was 166.6 mm and 17.64 g, respectively. The average absolute fecundity and relative fecundity of C. nasus were (3.10±2.16)×104 eggs and (605.42±181.85) eggs/g, respectively. The egg diameter was (615.47±107.30) μm on average, and exhibited a unimodal distribution, which indicated a single spawning type. The average gonadosomatic index (GSI) was (6.32±4.52)% for females and (3.74±1.63)% for males, while the average hepatosomatic index (HSI) was (1.15±1.10)% for females and (0.63±0.53)% for males, respectively. Compared with the studies on C. nasus in the TGRR and other Yangtze River waters prior, the current spawning population in the TGRR tends to be shifting towards characteristics of an r-strategist, which is reducing egg size and increasing absolute fecundity. In conclusion, the stable population structure and size of C. nasus suggest that it has fully adapted to the environment of the TGRR. Its distribution range is likely to expand further into other upstream waters of the Yangtze River, including both the mainstem and its tributaries.
2026,(2):000-000, DOI: 10.18307/2026.0200
Available online: November 12, 2025
Abstract:
Assessments of the ecological condition of Chinese waterbodies have substantially increased in recent years; however, the field remains in an early stage of development, facing challenges such as an incomplete theoretical framework, imprecise assessment methods, and limited comparability across studies. To draw upon mature international experience and promote scientific progress in our country, this review synthesizes the guiding role of ecological knowledge in aquatic ecological assessments and provides recommendations for improving their application in China. Fundamentally, biota–environment relationships form the theoretical basis of aquatic ecological assessment; in particular, niche theory and community-assembly (metacommunity) theory have exerted a decisive influence on the evolution of assessment paradigms, the optimization of assessment indices, and the improvement of assessment performance, i.e., the effectiveness of the assessment in indicating anthropogenic disturbance. Assessment approaches have progressed through several stages, evolving from early physico-chemistry - based evaluations to the current paradigm centered on biological assessment with physico-chemical indices as supporting measures. Diagnostic approaches that integrate quantitative assessment of ecological condition with identification of environmental stressors have now become the prevailing framework. In developing assessment indices, increasing emphasis has been placed on biological functional traits as sensitive metrics of environmental change. Consequently, multimetric indices that integrate disturbance-tolerant taxa, biodiversity, and functional traits have become widely adopted. The performance of assessment methods is commonly evaluated across several dimensions - precision, bias, responsiveness, sensitivity, and consistency. To improve assessment performance, unified survey and analytical procedures are essential, along with the use of anthropogenetic disturbance indicators to define reference conditions and predictive models to control for natural variability. Despite these advances, the ecological foundations underlying reference condition and ecological class criteria setting, and stressor diagnosis remain insufficiently developed. Strengthening these theoretical bases is therefore critical for further improving assessment performance. International experience indicates that aquatic ecological assessment must be firmly grounded in ecological theory. Recent efforts for assessment practices in China should prioritize accounting for the influence of natural factors, selecting metrics empirically from survey data, and implementing diagnostic frameworks that explicitly link ecological condition to causal stressors. Advancing these elements will consolidate the scientific foundation of aquatic assessment, foster its transition toward greater precision, standardization, and automation, and ultimately provide stronger scientific support for aquatic ecological management and international environmental commitments.
Assessments of the ecological condition of Chinese waterbodies have substantially increased in recent years; however, the field remains in an early stage of development, facing challenges such as an incomplete theoretical framework, imprecise assessment methods, and limited comparability across studies. To draw upon mature international experience and promote scientific progress in our country, this review synthesizes the guiding role of ecological knowledge in aquatic ecological assessments and provides recommendations for improving their application in China. Fundamentally, biota–environment relationships form the theoretical basis of aquatic ecological assessment; in particular, niche theory and community-assembly (metacommunity) theory have exerted a decisive influence on the evolution of assessment paradigms, the optimization of assessment indices, and the improvement of assessment performance, i.e., the effectiveness of the assessment in indicating anthropogenic disturbance. Assessment approaches have progressed through several stages, evolving from early physico-chemistry - based evaluations to the current paradigm centered on biological assessment with physico-chemical indices as supporting measures. Diagnostic approaches that integrate quantitative assessment of ecological condition with identification of environmental stressors have now become the prevailing framework. In developing assessment indices, increasing emphasis has been placed on biological functional traits as sensitive metrics of environmental change. Consequently, multimetric indices that integrate disturbance-tolerant taxa, biodiversity, and functional traits have become widely adopted. The performance of assessment methods is commonly evaluated across several dimensions - precision, bias, responsiveness, sensitivity, and consistency. To improve assessment performance, unified survey and analytical procedures are essential, along with the use of anthropogenetic disturbance indicators to define reference conditions and predictive models to control for natural variability. Despite these advances, the ecological foundations underlying reference condition and ecological class criteria setting, and stressor diagnosis remain insufficiently developed. Strengthening these theoretical bases is therefore critical for further improving assessment performance. International experience indicates that aquatic ecological assessment must be firmly grounded in ecological theory. Recent efforts for assessment practices in China should prioritize accounting for the influence of natural factors, selecting metrics empirically from survey data, and implementing diagnostic frameworks that explicitly link ecological condition to causal stressors. Advancing these elements will consolidate the scientific foundation of aquatic assessment, foster its transition toward greater precision, standardization, and automation, and ultimately provide stronger scientific support for aquatic ecological management and international environmental commitments.
2026,(3):000-000, DOI: 10.18307/2026.0342
Available online: November 06, 2025
Abstract:
Abstract: Lake topography, as a core element of the geographical environment, holds multifaceted significance in geographical research. It exerts fundamental influence on surface processes, particularly in hydrological and hydrodynamic modeling. Given that traditional methods for acquiring bathymetric data in large lakes are cost-intensive, time-consuming, and yield infrequent updates, it is imperative to develop rapid satellite remote sensing-based approaches for lake topography mapping. This study utilizes the Random Forest (RF) algorithm combined with Landsat remote sensing imagery and measured elevation data to inverse the local topography of Poyang Lake during the dry season. To address the spatial non-stationarity of topographic features and the spatial autocorrelation of prediction residuals, this study integrates Geographically Weighted Regression (GWR) with Ordinary Kriging (OK) methods to optimize the inversion results and analyzes its errors. The results show that: (1) compared with the RF model, the accuracy of the geographically weighted regression random forest kriging hybrid model (GWR-RF-OK) is significantly improved, and the coefficient of determination (R2) of the measured and inverted elevations in the two study areas are increased, and the mean absolute error (MAE) and mean relative error (MRE) are decreased. (2) The hybrid model has better inversion effect in both the bare beach area with single surface cover type and the Nanji Wetland National Nature Reserve of Poyang Lake (hereinafter referred to as Nanji Wetland Area), which has relatively complex surface cover types, with the R2 of 0.71 and 0.56, the MAE of 0.34m and 0.35m, and the MRE of 5.26% and 3.06%, respectively. After segmentation analysis, the model has better inversion effect in areas with topographic elevation greater than 10m. (3) The degree of topographic relief and the type of surface cover affects the accuracy of the inversion, with the error being smaller in areas with gentle topography than in areas with steep topography, and the accuracy of the topographic inversion of the same type of surface cover in areas with a single surface cover is significantly better than that in areas with a mixture of multiple surface cover types.
Abstract: Lake topography, as a core element of the geographical environment, holds multifaceted significance in geographical research. It exerts fundamental influence on surface processes, particularly in hydrological and hydrodynamic modeling. Given that traditional methods for acquiring bathymetric data in large lakes are cost-intensive, time-consuming, and yield infrequent updates, it is imperative to develop rapid satellite remote sensing-based approaches for lake topography mapping. This study utilizes the Random Forest (RF) algorithm combined with Landsat remote sensing imagery and measured elevation data to inverse the local topography of Poyang Lake during the dry season. To address the spatial non-stationarity of topographic features and the spatial autocorrelation of prediction residuals, this study integrates Geographically Weighted Regression (GWR) with Ordinary Kriging (OK) methods to optimize the inversion results and analyzes its errors. The results show that: (1) compared with the RF model, the accuracy of the geographically weighted regression random forest kriging hybrid model (GWR-RF-OK) is significantly improved, and the coefficient of determination (R2) of the measured and inverted elevations in the two study areas are increased, and the mean absolute error (MAE) and mean relative error (MRE) are decreased. (2) The hybrid model has better inversion effect in both the bare beach area with single surface cover type and the Nanji Wetland National Nature Reserve of Poyang Lake (hereinafter referred to as Nanji Wetland Area), which has relatively complex surface cover types, with the R2 of 0.71 and 0.56, the MAE of 0.34m and 0.35m, and the MRE of 5.26% and 3.06%, respectively. After segmentation analysis, the model has better inversion effect in areas with topographic elevation greater than 10m. (3) The degree of topographic relief and the type of surface cover affects the accuracy of the inversion, with the error being smaller in areas with gentle topography than in areas with steep topography, and the accuracy of the topographic inversion of the same type of surface cover in areas with a single surface cover is significantly better than that in areas with a mixture of multiple surface cover types.
Xinfeng Zhuang, Haoran Tang, Xingchen Zhao, Yaxuan Li, Jin Wang, Minglei Ren, Ze Ren, Wei Zhang, Jihong Peng, Jianming Deng
2026,(3):000-000, DOI: 10.18307/2026.0338
Available online: November 06, 2025
Abstract:
In the context of global climate change, the frequency and intensity of extreme heat events (heat waves) have increased significantly, posing potential threats to the stability of lake ecosystems. To assess these impacts, this study simulated short-term heat waves using the Middle Universe Simulation System. A combined metagenomic and metatranscriptomic sequencing approach was applied to systematically examine structural and functional responses of lake aquatic microbial communities. The results showed that microbial community composition remained largely stable under short-term high-temperature stress, whereas functional diversity increased markedly, with 467 unique functions detected compared to the control group. Moreover, gene expression levels exhibited substantial changes, particularly in metabolic pathways and photosynthetic processes. The Bray–Curtis analysis further revealed an increase of 0.12 in community compositional distance and 0.16 in functional distance following heat wave exposure. These findings indicate that heat waves primarily affect aquatic ecological processes by driving shifts in functional diversity. Overall, aquatic microbial communities appear capable of rapidly adapting to environmental fluctuations through functional adjustments, while structural changes occur more slowly.
In the context of global climate change, the frequency and intensity of extreme heat events (heat waves) have increased significantly, posing potential threats to the stability of lake ecosystems. To assess these impacts, this study simulated short-term heat waves using the Middle Universe Simulation System. A combined metagenomic and metatranscriptomic sequencing approach was applied to systematically examine structural and functional responses of lake aquatic microbial communities. The results showed that microbial community composition remained largely stable under short-term high-temperature stress, whereas functional diversity increased markedly, with 467 unique functions detected compared to the control group. Moreover, gene expression levels exhibited substantial changes, particularly in metabolic pathways and photosynthetic processes. The Bray–Curtis analysis further revealed an increase of 0.12 in community compositional distance and 0.16 in functional distance following heat wave exposure. These findings indicate that heat waves primarily affect aquatic ecological processes by driving shifts in functional diversity. Overall, aquatic microbial communities appear capable of rapidly adapting to environmental fluctuations through functional adjustments, while structural changes occur more slowly.
2026,(3):000-000, DOI: 10.18307/2026.0336
Available online: November 06, 2025
Abstract:
The lake area in the middle and lower reaches of the Yangtze River represents a significant concentration of freshwater lakes in China, with its biodiversity facing considerable challenges stemming from prolonged river-lake disconnection. While previous research has examined the impacts of river-lake disconnection on aquatic biodiversity, there remains a dearth of studies focusing on the taxonomic distinctness diversity of mollusk communities over long-term scales. To address this gap, this study selected seven representative lakes (comprising five disconnected lakes and two remaining connected lakes) in the middle and lower reaches of the Yangtze River, to investigate changes in the taxonomic distinctness indices of mollusk communities by comparing data from historical and contemporary periods. The findings revealed a notable decline in total species richness (from 152 to 83 species), with the average species richness decreasing from 57.7 to 30.1 (a 47.8% reduction). From the historical period to current period, the average taxonomic distinctness Δ+ and variation in taxonomic distinctness Λ+ of entire mollusks, gastropods and bivalves all remained relatively stable, except for a significant increase in the Δ+ of gastropods. Compared to the two connected lakes, the five disconnected lakes exhibited more pronounced changes in Δ+ and Λ+ indices: the Δ+ of entire mollusks (t = -3.551，p = 0.024) and gastropods (t = -2.774，p = 0.050) both significantly increased over time,while the Λ+ of entire mollusks significantly decreased(t = 2.297，p = 0.083). Additionally, in the funnel plot analysis based on the Δ+ and Λ+ indices, the disconnected lakes were predominantly located within the 95% confidence interval, while the connected lakes fell outside this range. The increase in Δ+ and decrease in Λ+ observed in mollusk communities across the five disconnected lakes were primarily driven by the significant loss of congeneric and endemic species (such as with the genera Sinotaia,Cipangopaludina,Lamprotula,and Aculamprotula). Such loss of these congeneric endemic species from the families Viviparidae and Unionidae should be regarded as a critical warning signal of biodiversity decline caused by river-lake disconnection. The findings provide scientific basis for the management and conservation of mollusk resources and diversity,as well as the ecological restoration of lakes in the middle and lower reaches of the Yangtze River under the background of river-lake disconnection.
The lake area in the middle and lower reaches of the Yangtze River represents a significant concentration of freshwater lakes in China, with its biodiversity facing considerable challenges stemming from prolonged river-lake disconnection. While previous research has examined the impacts of river-lake disconnection on aquatic biodiversity, there remains a dearth of studies focusing on the taxonomic distinctness diversity of mollusk communities over long-term scales. To address this gap, this study selected seven representative lakes (comprising five disconnected lakes and two remaining connected lakes) in the middle and lower reaches of the Yangtze River, to investigate changes in the taxonomic distinctness indices of mollusk communities by comparing data from historical and contemporary periods. The findings revealed a notable decline in total species richness (from 152 to 83 species), with the average species richness decreasing from 57.7 to 30.1 (a 47.8% reduction). From the historical period to current period, the average taxonomic distinctness Δ+ and variation in taxonomic distinctness Λ+ of entire mollusks, gastropods and bivalves all remained relatively stable, except for a significant increase in the Δ+ of gastropods. Compared to the two connected lakes, the five disconnected lakes exhibited more pronounced changes in Δ+ and Λ+ indices: the Δ+ of entire mollusks (t = -3.551，p = 0.024) and gastropods (t = -2.774，p = 0.050) both significantly increased over time,while the Λ+ of entire mollusks significantly decreased(t = 2.297，p = 0.083). Additionally, in the funnel plot analysis based on the Δ+ and Λ+ indices, the disconnected lakes were predominantly located within the 95% confidence interval, while the connected lakes fell outside this range. The increase in Δ+ and decrease in Λ+ observed in mollusk communities across the five disconnected lakes were primarily driven by the significant loss of congeneric and endemic species (such as with the genera Sinotaia,Cipangopaludina,Lamprotula,and Aculamprotula). Such loss of these congeneric endemic species from the families Viviparidae and Unionidae should be regarded as a critical warning signal of biodiversity decline caused by river-lake disconnection. The findings provide scientific basis for the management and conservation of mollusk resources and diversity,as well as the ecological restoration of lakes in the middle and lower reaches of the Yangtze River under the background of river-lake disconnection.
2026,(3):000-000, DOI: 10.18307/2026.0341
Available online: November 05, 2025
Abstract:
Residence time serves as a critical indicator of lake water renewal and exchange, directly influencing pollutant transport and migration processes, and consequently water environment of the lake. In recent years, the hydrological conditions of Poyang Lake have undergone substantial changes, which have significantly influenced its water environment. This study focuses on residence time as a crucial hydrodynamic parameter for assessing water quality. Using the MIKE21 hydrodynamic model coupled with a tracer model, the research quantitatively examines the spatiotemporal distribution characteristics of residence time during the receding period of Poyang Lake from 1980 to 2020. Additionally, the study investigates regional interannual variation trends and clarifies the response relationship between residence time and hydrological conditions. The results reveal that the residence time during the receding period of Poyang Lake is characterized by high spatiotemporal heterogeneity. The average residence time for the entire lake is 36 d, with variations among sub-regions: eastern lake bays (93 d) > southern lake area (53 d) > northern channels (38 d) > main lake area (26 d) > seasonal isolated lakes of Wucheng (17 d). Over the past 40 years, certain areas of Poyang Lake have experienced a slight decreasing trend in average residence time. After the operation of Three Gorges Dam, the average residence time of the entire lake decreases by about 4 d, with the northern channels exhibiting the largest decrease (9 d), followed by the main lake area (5 d); other regions show minimal change. The residence time during the receding period of Poyang Lake is significantly longer in wet years compared to dry years. A strong positive correlation exists between residence rate and water level during the receding period. The shortened residence time during the receding period in Poyang Lake is primarily attributed to the decreased water level and the accelerated recession rate. The results of this study can provide scientific support for the water environment governance and ecological restoration of Poyang Lake.
Residence time serves as a critical indicator of lake water renewal and exchange, directly influencing pollutant transport and migration processes, and consequently water environment of the lake. In recent years, the hydrological conditions of Poyang Lake have undergone substantial changes, which have significantly influenced its water environment. This study focuses on residence time as a crucial hydrodynamic parameter for assessing water quality. Using the MIKE21 hydrodynamic model coupled with a tracer model, the research quantitatively examines the spatiotemporal distribution characteristics of residence time during the receding period of Poyang Lake from 1980 to 2020. Additionally, the study investigates regional interannual variation trends and clarifies the response relationship between residence time and hydrological conditions. The results reveal that the residence time during the receding period of Poyang Lake is characterized by high spatiotemporal heterogeneity. The average residence time for the entire lake is 36 d, with variations among sub-regions: eastern lake bays (93 d) > southern lake area (53 d) > northern channels (38 d) > main lake area (26 d) > seasonal isolated lakes of Wucheng (17 d). Over the past 40 years, certain areas of Poyang Lake have experienced a slight decreasing trend in average residence time. After the operation of Three Gorges Dam, the average residence time of the entire lake decreases by about 4 d, with the northern channels exhibiting the largest decrease (9 d), followed by the main lake area (5 d); other regions show minimal change. The residence time during the receding period of Poyang Lake is significantly longer in wet years compared to dry years. A strong positive correlation exists between residence rate and water level during the receding period. The shortened residence time during the receding period in Poyang Lake is primarily attributed to the decreased water level and the accelerated recession rate. The results of this study can provide scientific support for the water environment governance and ecological restoration of Poyang Lake.
2026,(3):000-000, DOI: 10.18307/2026.0324
Available online: November 05, 2025
Abstract:
As a strategic water conservancy project in the lower reaches of the Yangtze River in China, the project has multiple missions such as alleviating the shortage of water resources in Huaibei, improving the ecology of Chaohu Lake and Huaihe River, and promoting the sustainable development of the river basin. Dissolved organic matter (DOM) is an important indicator for assessing the health status of water bodies and tracing pollution sources. Study on its response process to inter-basin water transfers can accurately track the characteristics of water quality changes induced by such transfers, which is of great significance for optimizing ecological scheduling strategies and ensuring water environmental security in the Jiang-huai region. In this study, we selected the Yangtze-Chao section and Yangtze-Huai section in the water diversion project from the Yangtze River to Huaihe River (Anhui section), systematically analysed the source, composition and distribution characteristics of dissolved organic matter (DOM) and its influencing factors in the water diversion project (Anhui section) from the Yangtze River to Huaihe River at the different hydrological periods from December 2023 to June 2024. The results show as follows: (1) the concentration of total nitrogen (TN), ammonia nitrogen and permanganate index (CODMn) in the water bodies during the different hydrological periods showed increasing trends in the dry season, wet season and normal flow season, and their concentrations decreased after water diversion, especially in the Yangtze-Huai section the concentration of TN decreasing from 4.00±1.45 mg/L to 2.06±0.58 mg/L. TP concentration did not change with the spatial and seasonal distributions. DOC concentration showed significant seasonal and spatial variation. During the dry season, the concentrations of DOC in lakes and estuaries were relatively high, while DOC in river section was low. (2) Four DOM fluorescent components were identified, namely marine-derived humus C1, funic acid humic C2, humic acid C3, and tryptophan group proteins C4. DOM was both influenced by autogenic and terrestrial sources. There is no significant seasonal variation in the proportion of autogenic and terrestrial organic matter in the water during different hydrological periods. After water regulation, there is no obvious difference in the spatial distribution characteristics of DOM fluorescence intensity and DOC concentration due to water exchange. (3) TN, CODMn, DO, Chl-a and WT had a significant impact on the composition and concentration of DOM, while the increase of water temperature and DO had a promoting effect on algae growth and degradation of organic matter. The increase of TN concentration led to the eutrophication of water body and the accumulation of DOM. This study evaluated the water environment quality along the Anhui section of the Yangtze-to-Huaihe water diversion project after its initial implementation of water diversion. It reveals the response patterns of DOM in the early stages of inter-basin water transfer and provides a scientific basis for scheduling the water diversion project from a water quality safety perspective.
As a strategic water conservancy project in the lower reaches of the Yangtze River in China, the project has multiple missions such as alleviating the shortage of water resources in Huaibei, improving the ecology of Chaohu Lake and Huaihe River, and promoting the sustainable development of the river basin. Dissolved organic matter (DOM) is an important indicator for assessing the health status of water bodies and tracing pollution sources. Study on its response process to inter-basin water transfers can accurately track the characteristics of water quality changes induced by such transfers, which is of great significance for optimizing ecological scheduling strategies and ensuring water environmental security in the Jiang-huai region. In this study, we selected the Yangtze-Chao section and Yangtze-Huai section in the water diversion project from the Yangtze River to Huaihe River (Anhui section), systematically analysed the source, composition and distribution characteristics of dissolved organic matter (DOM) and its influencing factors in the water diversion project (Anhui section) from the Yangtze River to Huaihe River at the different hydrological periods from December 2023 to June 2024. The results show as follows: (1) the concentration of total nitrogen (TN), ammonia nitrogen and permanganate index (CODMn) in the water bodies during the different hydrological periods showed increasing trends in the dry season, wet season and normal flow season, and their concentrations decreased after water diversion, especially in the Yangtze-Huai section the concentration of TN decreasing from 4.00±1.45 mg/L to 2.06±0.58 mg/L. TP concentration did not change with the spatial and seasonal distributions. DOC concentration showed significant seasonal and spatial variation. During the dry season, the concentrations of DOC in lakes and estuaries were relatively high, while DOC in river section was low. (2) Four DOM fluorescent components were identified, namely marine-derived humus C1, funic acid humic C2, humic acid C3, and tryptophan group proteins C4. DOM was both influenced by autogenic and terrestrial sources. There is no significant seasonal variation in the proportion of autogenic and terrestrial organic matter in the water during different hydrological periods. After water regulation, there is no obvious difference in the spatial distribution characteristics of DOM fluorescence intensity and DOC concentration due to water exchange. (3) TN, CODMn, DO, Chl-a and WT had a significant impact on the composition and concentration of DOM, while the increase of water temperature and DO had a promoting effect on algae growth and degradation of organic matter. The increase of TN concentration led to the eutrophication of water body and the accumulation of DOM. This study evaluated the water environment quality along the Anhui section of the Yangtze-to-Huaihe water diversion project after its initial implementation of water diversion. It reveals the response patterns of DOM in the early stages of inter-basin water transfer and provides a scientific basis for scheduling the water diversion project from a water quality safety perspective.
2026,(3):000-000, DOI: 10.18307/2026.0345
Available online: November 05, 2025
Abstract:
Affected by global climate change and anthropogenic activities, the degree of saltwater intrusion in China tidal river sections has been intensifying, posing a serious threat to the water-using safety and ecological stability in estuarine areas. The need for saltwater intrusion control is becoming increasingly urgent. Based on the finite volume ocean model, a hydrodynamic salinity numerical model of the estuary area was constructed with the downstream reaches of the Min River as the research region. The model simulated the saltwater intrusion scenario under extreme drought events and explored the influence regulation of upstream reservoir scheduling on saltwater intrusion. The results demonstrate that increasing the discharge flow from upstream reservoirs can significantly reduce the degree of saltwater intrusion. Under the ex-tremely drought conditions during the 2022 dry season, an increase of 240% in reservoir discharge could effectively push the saltwater intrusion boundary back to the confluence of the North Channel and the South Channel. When upstream reservoirs discharge was increased at varying gradients, the morphological differences between the North Channel and the South Channel led to uneven flow distribution, thereby differentially affecting saltwater retreat in the two channels. At an 80% increase in upstream discharge, the North Channel exhibited the maximum retreat of the saltwater intrusion front, beyond which the retreat rate diminished with further flow increases. In contrast, the South Channel showed a propor-tional retreat of the saltwater intrusion front with each incremental doubling of upstream discharge. In addition, when the upstream flow increased in a gradient manner, the longitudinal salinity along the lower reach was significantly reduced, with the largest decrease when the flow increased by 80%, and then the decrease became smaller. This study provides guidance and scientific basis for the formulation and implementation of prevention strategies for saltwater intrusion events in tidal rivers.
Affected by global climate change and anthropogenic activities, the degree of saltwater intrusion in China tidal river sections has been intensifying, posing a serious threat to the water-using safety and ecological stability in estuarine areas. The need for saltwater intrusion control is becoming increasingly urgent. Based on the finite volume ocean model, a hydrodynamic salinity numerical model of the estuary area was constructed with the downstream reaches of the Min River as the research region. The model simulated the saltwater intrusion scenario under extreme drought events and explored the influence regulation of upstream reservoir scheduling on saltwater intrusion. The results demonstrate that increasing the discharge flow from upstream reservoirs can significantly reduce the degree of saltwater intrusion. Under the ex-tremely drought conditions during the 2022 dry season, an increase of 240% in reservoir discharge could effectively push the saltwater intrusion boundary back to the confluence of the North Channel and the South Channel. When upstream reservoirs discharge was increased at varying gradients, the morphological differences between the North Channel and the South Channel led to uneven flow distribution, thereby differentially affecting saltwater retreat in the two channels. At an 80% increase in upstream discharge, the North Channel exhibited the maximum retreat of the saltwater intrusion front, beyond which the retreat rate diminished with further flow increases. In contrast, the South Channel showed a propor-tional retreat of the saltwater intrusion front with each incremental doubling of upstream discharge. In addition, when the upstream flow increased in a gradient manner, the longitudinal salinity along the lower reach was significantly reduced, with the largest decrease when the flow increased by 80%, and then the decrease became smaller. This study provides guidance and scientific basis for the formulation and implementation of prevention strategies for saltwater intrusion events in tidal rivers.
2026,(3):000-000, DOI: 10.18307/2026.0326
Available online: November 05, 2025
Abstract:
Wetlands represent crucial carbon reservoirs within terrestrial ecosystems, functioning as either carbon sources or sinks through complex carbon cycling processes. However, the day-night variations in CO? flux across wetland environments remain inadequately understood, creating uncertainty in accurate assessments of wetland carbon sequestration capacity. This study investigated the temporal dynamics and controlling factors of CO? flux in Poyang Lake wetland during 2021 (a normal flow year), employing eddy covariance measurements with partial correlation and multiple regression analyses during both exposed and inundation periods. The results show that: (1) During the exposed period (January-April and November-December), diurnal CO? flux exhibited characteristic "U"-shaped variations, functioning as a carbon sink during daylight hours and a carbon source at night. Conversely, during the inundation period (May-October), CO? flux remained near zero, though with notable day-night fluctuations emerging during late inundation (September-October). (2) Monthly analyses showed significant day-night CO? flux differences during exposed periods that diminished during inundation, closely corresponding with the transformation between carbon source and sink functions. (3) Annual assessments demonstrated pronounced day-night variations, with average nighttime flux exceeding daytime by 25.5%; this diurnal difference peaked during exposed periods (averaging 10.22 μmol·m?2·s?1). (4) Controlling factors varied by period: during exposed periods, daytime CO2 flux was primarily regulated by incident shortwave radiation and soil moisture, while nighttime CO2 flux was dominated by soil temperature; during inundation, daytime CO2 flux responded mainly to precipitation and soil moisture, while nighttime CO2 flux was jointly influenced by soil moisture, lake water level, and soil temperature. (5) The fundamental mechanisms driving these diurnal differences were period-dependent. During exposed periods, biological processes, including photosynthesis (daytime) and respiration (nighttime), created distinct carbon sink-source dynamics. During inundation, water coverage suppressed both plant and microbial activities, consequently reducing day-night CO2 flux variations. These findings elucidate the diurnal mechanisms governing wetland CO? flux, providing valuable scientific basis for integrated carbon-water resource management and wetland ecological protection.
Wetlands represent crucial carbon reservoirs within terrestrial ecosystems, functioning as either carbon sources or sinks through complex carbon cycling processes. However, the day-night variations in CO? flux across wetland environments remain inadequately understood, creating uncertainty in accurate assessments of wetland carbon sequestration capacity. This study investigated the temporal dynamics and controlling factors of CO? flux in Poyang Lake wetland during 2021 (a normal flow year), employing eddy covariance measurements with partial correlation and multiple regression analyses during both exposed and inundation periods. The results show that: (1) During the exposed period (January-April and November-December), diurnal CO? flux exhibited characteristic "U"-shaped variations, functioning as a carbon sink during daylight hours and a carbon source at night. Conversely, during the inundation period (May-October), CO? flux remained near zero, though with notable day-night fluctuations emerging during late inundation (September-October). (2) Monthly analyses showed significant day-night CO? flux differences during exposed periods that diminished during inundation, closely corresponding with the transformation between carbon source and sink functions. (3) Annual assessments demonstrated pronounced day-night variations, with average nighttime flux exceeding daytime by 25.5%; this diurnal difference peaked during exposed periods (averaging 10.22 μmol·m?2·s?1). (4) Controlling factors varied by period: during exposed periods, daytime CO2 flux was primarily regulated by incident shortwave radiation and soil moisture, while nighttime CO2 flux was dominated by soil temperature; during inundation, daytime CO2 flux responded mainly to precipitation and soil moisture, while nighttime CO2 flux was jointly influenced by soil moisture, lake water level, and soil temperature. (5) The fundamental mechanisms driving these diurnal differences were period-dependent. During exposed periods, biological processes, including photosynthesis (daytime) and respiration (nighttime), created distinct carbon sink-source dynamics. During inundation, water coverage suppressed both plant and microbial activities, consequently reducing day-night CO2 flux variations. These findings elucidate the diurnal mechanisms governing wetland CO? flux, providing valuable scientific basis for integrated carbon-water resource management and wetland ecological protection.
2026,(3):000-000, DOI: 10.18307/2026.0302
Available online: November 05, 2025
Abstract:
The construction of dams and reservoirs has profoundly altered the natural flow regimes of nearly two-thirds of the world"s major rivers exceeding 1,000 kilometers in length. With more than 90,000 water reservoirs, China ranked the 1st in the world for the number of reservoirs. A series of complex factors, including the dam"s trapping effect, hydraulic scheduling, local hydrometeorology, sediment inputs etc., not only shape reservoir sediments as a unique habitat, but also influence the diversity and functionality of microbial communities in the sediments. Microorganisms are the fundamental drivers of material cycling in the aquatic environment system and have important influences on the structure of watershed ecosystem, biogeochemical cyclings of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, biological conditions, but also by dynamically influencing the spatiotemporal distribution of environmental-ecological conditions. In response, microbial communities in sediment also react by altering surrounding environmental conditions to some extent. Existing studies on individual factors, although relatively complete, lack systematicity, which hinders further in-depth understanding of the important interactions between microorganisms and hydraulic and ecological environment. Therefore, 189 related research articles have been collected and analyzed by the 7th May, 2025, and this article reviews the physical, chemical, ecological impacts of reservoirs on sediment microbial communities, classifies and summarizes a series of responses of sediment microbial communities under hydrological regulation, and summarizes the environmental and ecological impacts brought by microbial communities. Results show that, most of the existing studies consider reservoirs as lake-like habitats, and few studies consider changes in hydraulic conditions or special characteristics of the habitat; although there are studies targeting microorganisms in sediments of water reservoirs, they are more focused on the biogeographical distribution patterns and less on the interactions between environment and microbial communities. Faced with the deficiencies in current research, it is recommended to strengthen the integration of interdisciplinary fields, and to carry out in-depth related research in the fields of ecological and environmental effects of microbial communities, application of microbial ecology techniques and theories, development of big data and artificial intelligence models, global climate change and greenhouse gas emission reduction, etc.
The construction of dams and reservoirs has profoundly altered the natural flow regimes of nearly two-thirds of the world"s major rivers exceeding 1,000 kilometers in length. With more than 90,000 water reservoirs, China ranked the 1st in the world for the number of reservoirs. A series of complex factors, including the dam"s trapping effect, hydraulic scheduling, local hydrometeorology, sediment inputs etc., not only shape reservoir sediments as a unique habitat, but also influence the diversity and functionality of microbial communities in the sediments. Microorganisms are the fundamental drivers of material cycling in the aquatic environment system and have important influences on the structure of watershed ecosystem, biogeochemical cyclings of elements, global climate change, etc. Reservoirs alter sediment microbial communities not only via the changes of a variety of physical, chemical, biological conditions, but also by dynamically influencing the spatiotemporal distribution of environmental-ecological conditions. In response, microbial communities in sediment also react by altering surrounding environmental conditions to some extent. Existing studies on individual factors, although relatively complete, lack systematicity, which hinders further in-depth understanding of the important interactions between microorganisms and hydraulic and ecological environment. Therefore, 189 related research articles have been collected and analyzed by the 7th May, 2025, and this article reviews the physical, chemical, ecological impacts of reservoirs on sediment microbial communities, classifies and summarizes a series of responses of sediment microbial communities under hydrological regulation, and summarizes the environmental and ecological impacts brought by microbial communities. Results show that, most of the existing studies consider reservoirs as lake-like habitats, and few studies consider changes in hydraulic conditions or special characteristics of the habitat; although there are studies targeting microorganisms in sediments of water reservoirs, they are more focused on the biogeographical distribution patterns and less on the interactions between environment and microbial communities. Faced with the deficiencies in current research, it is recommended to strengthen the integration of interdisciplinary fields, and to carry out in-depth related research in the fields of ecological and environmental effects of microbial communities, application of microbial ecology techniques and theories, development of big data and artificial intelligence models, global climate change and greenhouse gas emission reduction, etc.
2026,(3):000-000, DOI: 10.18307/2026.0353
Available online: November 04, 2025
Abstract:
Under the combined pressures of climate change and human activities, lake ecosystems across different regions of the Poyang Lake Basin have experienced varying degrees of degradation. A deep understanding of the long-term evolution and pattern of the lake basin environment is of great significance for the ecological restoration and conservation of Poyang Lake. Based on 21?Pb dating, this study employs a multi-proxy analysis including total organic carbon (TOC), total nitrogen (TN), their molar ratio (C/N ratio), organic carbon accumulation rate (OCAR), total nitrogen accumulation rate (TNAR), and stable carbon isotope of organic matter (δ13C??g) in sediments from Junshan Lake and Qinglan Lake in the southern Poyang Lake basin. It reveals the main sources of sedimentary organic matter and potential mechanisms driving changes in lake primary productivity and eutrophication processes over the past century. The results indicate that the C/N ratios and δ13C??g values in Junshan Lake ranged from 7.7 – 10.5 and -23.9‰ to -22.0‰, respectively, while in Qinglan Lake they ranged from 8.7 – 11.3 and -26.3‰ to -21.7‰. This suggests that sedimentary organic matter in both lakes primarily originated from macrophytes (large aquatic plants) and phytoplankton. Post-1905 in Junshan Lake and post-1980 in Qinglan Lake, TOC and TN concentrations showed an increasing trend, reflecting a common characteristic of gradually rising lake primary productivity. The differences in the response of δ13Corg to changes in primary productivity of different types of lakes reflected the differences in the composition of aquatic plant communities. Specifically, Junshan Lake, primarily influenced by climate warming and aquaculture activities, has undergone a successional shift over the past two centuries: from macrophyte dominance, through a phase of macrophyte-algae codominance, to the current state of algal dominance. In contrast, Qinglan Lake experienced a decline in submerged vegetation following the diversion of the river in 1958, largely due to increased sediment input. After 1980, superimposed impacts from domestic sewage and agricultural non-point source pollution associated with urbanization further accelerated this trend. Consequently, phytoplankton has become the dominant source of sedimentary organic matter in Qinglan Lake. Furthermore, this study compares the ecological environment evolution in different sub-regions of Poyang Lake, providing a scientific basis for understanding their divergent characteristics and clarifying the mechanisms of ecological degradation driven by the coupling of multiple factors.
Under the combined pressures of climate change and human activities, lake ecosystems across different regions of the Poyang Lake Basin have experienced varying degrees of degradation. A deep understanding of the long-term evolution and pattern of the lake basin environment is of great significance for the ecological restoration and conservation of Poyang Lake. Based on 21?Pb dating, this study employs a multi-proxy analysis including total organic carbon (TOC), total nitrogen (TN), their molar ratio (C/N ratio), organic carbon accumulation rate (OCAR), total nitrogen accumulation rate (TNAR), and stable carbon isotope of organic matter (δ13C??g) in sediments from Junshan Lake and Qinglan Lake in the southern Poyang Lake basin. It reveals the main sources of sedimentary organic matter and potential mechanisms driving changes in lake primary productivity and eutrophication processes over the past century. The results indicate that the C/N ratios and δ13C??g values in Junshan Lake ranged from 7.7 – 10.5 and -23.9‰ to -22.0‰, respectively, while in Qinglan Lake they ranged from 8.7 – 11.3 and -26.3‰ to -21.7‰. This suggests that sedimentary organic matter in both lakes primarily originated from macrophytes (large aquatic plants) and phytoplankton. Post-1905 in Junshan Lake and post-1980 in Qinglan Lake, TOC and TN concentrations showed an increasing trend, reflecting a common characteristic of gradually rising lake primary productivity. The differences in the response of δ13Corg to changes in primary productivity of different types of lakes reflected the differences in the composition of aquatic plant communities. Specifically, Junshan Lake, primarily influenced by climate warming and aquaculture activities, has undergone a successional shift over the past two centuries: from macrophyte dominance, through a phase of macrophyte-algae codominance, to the current state of algal dominance. In contrast, Qinglan Lake experienced a decline in submerged vegetation following the diversion of the river in 1958, largely due to increased sediment input. After 1980, superimposed impacts from domestic sewage and agricultural non-point source pollution associated with urbanization further accelerated this trend. Consequently, phytoplankton has become the dominant source of sedimentary organic matter in Qinglan Lake. Furthermore, this study compares the ecological environment evolution in different sub-regions of Poyang Lake, providing a scientific basis for understanding their divergent characteristics and clarifying the mechanisms of ecological degradation driven by the coupling of multiple factors.
2026,(3):000-000, DOI: 10.18307/2026.0323
Available online: November 04, 2025
Abstract:
The numerous lakes distributed in Inner Mongolia have experienced problems of excessive fluoride concentration due to environmental changes, posing carcinogenic health risks to humans and the lakes themselves, as well as potential ecological risks. To deeply explore the characteristics of fluoride forms in lake sediments and reveal the response relationship between fluoride adsorption-desorption behavior and influencing factors, Daihai Lake was selected as the research object. Surface sediment samples were collected, and the contents of different forms of fluoride were detected through multi-stage extraction. ArcGIS software was used to analyze the temporal and spatial differences of fluoride. Further, a 4-factor, 3-level orthogonal simulation experiment of fluoride adsorption-desorption in sediments and a simulation experiment of adsorption-desorption kinetics model were designed to reveal the influence of environmental factors on the adsorption and desorption behavior of fluoride in cold and arid lake sediments. The results showed that the average total fluoride content in the sediments of Daihai Lake was 860.44 ± 53.64 mg·kg-1, with a range of 600.03 to 1388.67 mg·kg-1. Among them, the content ranges of water-soluble, exchangeable, iron-manganese-bound, and organic-bound fluoride were 29.51 to 42.87 mg·kg-1, 8.37 to 21.81 mg·kg-1, 2.46 to 7.21 mg·kg-1, and 9.79 to 17.59 mg·kg-1, respectively. The fitting analysis of the fluoride adsorption-desorption process in sediments indicated that the pseudo-second-order kinetic model had a higher fitting degree under different initial concentrations and could better describe the kinetic process of this adsorption system. The Langmuir and Freundlich thermodynamic models were used to fit and analyze the fluoride adsorption behavior, confirming that monolayer adsorption played a key role in the adsorption process, while multilayer adsorption on heterogeneous surfaces was also an important factor affecting the adsorption behavior. Through the range analysis and variance analysis of orthogonal experimental data, the influence degree and significance of each environmental factor on the adsorption effect were determined. Among them, temperature was the core driving factor for fluoride adsorption-desorption (ANOVA significance: temperature > initial concentration > disturbance intensity > pH). The optimal conditions were screened out based on k values: initial concentration of 10 mg·L-1, temperature of 20 ℃, pH of 7, and shaking frequency of 200 r·min-1. This study can provide important theoretical support for the prevention and control of fluoride release pollution from lake sediments in cold and arid regions.
The numerous lakes distributed in Inner Mongolia have experienced problems of excessive fluoride concentration due to environmental changes, posing carcinogenic health risks to humans and the lakes themselves, as well as potential ecological risks. To deeply explore the characteristics of fluoride forms in lake sediments and reveal the response relationship between fluoride adsorption-desorption behavior and influencing factors, Daihai Lake was selected as the research object. Surface sediment samples were collected, and the contents of different forms of fluoride were detected through multi-stage extraction. ArcGIS software was used to analyze the temporal and spatial differences of fluoride. Further, a 4-factor, 3-level orthogonal simulation experiment of fluoride adsorption-desorption in sediments and a simulation experiment of adsorption-desorption kinetics model were designed to reveal the influence of environmental factors on the adsorption and desorption behavior of fluoride in cold and arid lake sediments. The results showed that the average total fluoride content in the sediments of Daihai Lake was 860.44 ± 53.64 mg·kg-1, with a range of 600.03 to 1388.67 mg·kg-1. Among them, the content ranges of water-soluble, exchangeable, iron-manganese-bound, and organic-bound fluoride were 29.51 to 42.87 mg·kg-1, 8.37 to 21.81 mg·kg-1, 2.46 to 7.21 mg·kg-1, and 9.79 to 17.59 mg·kg-1, respectively. The fitting analysis of the fluoride adsorption-desorption process in sediments indicated that the pseudo-second-order kinetic model had a higher fitting degree under different initial concentrations and could better describe the kinetic process of this adsorption system. The Langmuir and Freundlich thermodynamic models were used to fit and analyze the fluoride adsorption behavior, confirming that monolayer adsorption played a key role in the adsorption process, while multilayer adsorption on heterogeneous surfaces was also an important factor affecting the adsorption behavior. Through the range analysis and variance analysis of orthogonal experimental data, the influence degree and significance of each environmental factor on the adsorption effect were determined. Among them, temperature was the core driving factor for fluoride adsorption-desorption (ANOVA significance: temperature > initial concentration > disturbance intensity > pH). The optimal conditions were screened out based on k values: initial concentration of 10 mg·L-1, temperature of 20 ℃, pH of 7, and shaking frequency of 200 r·min-1. This study can provide important theoretical support for the prevention and control of fluoride release pollution from lake sediments in cold and arid regions.
Zhou Bingqian, Zhang Xiaonan, Zhang Can, Niu Haoge, Niu Tingyu, Leng Mingrui, Zhao Xiangyu, Wang Qirui, He Xin, Yang Xiaoyi, Chen Liang, Zhang Hucai
2026,(3):000-000, DOI: 10.18307/2026.0317
Available online: November 03, 2025
Abstract:
Lake Dian, a typical plateau freshwater lake in China, has experienced increasingly severe eutrophication in recent years due to intensified human activities and continuous nutrient inputs. To elucidate the composition and sources of sterols in surface sediments of Lake Dian , this study conducted systematic multi-site sampling and analyzed the spatial distribution of sterol molecular markers, total organic carbon (TOC), total nitrogen (TN), and the C/N ratio, in conjunction with watershed land use patterns. The results revealed pronounced spatial heterogeneity in organic matter content and C/N ratios across the lake. The Caohai area, influenced by urban runoff and multiple river inflows, exhibited higher organic matter content and C/N values compared to Waihai, displaying a southwest-high, northeast-low gradient. In Waihai, deep central zones had greater organic matter content and C/N ratios than littoral shallow areas, forming a center-high, margin-low pattern. Sterol biomarker analysis indicated that C27 sterols (coprostanol, epicoprostanol, cholesterol, and cholestanol) were primarily enriched in Caohai and the northern and southeastern Waihai, reflecting significant inputs from domestic sewage and anthropogenic activities, C?? sterols, including coprostanol and epicoprostanol, were mainly distributed in Caohai, as well as in the northeastern and southern regions of Waihai, indicating strong influence from domestic sewage inputs. C28 and C29 sterols (campesterol, stigmasterol, and β-sitosterol) were enriched in Caohai as well as in the central and southern regions of Waihai,, indicating substantial higher plant inputs associated with intensive agricultural activity. C30 sterol (dinosterol) was notably elevated in the southern sediments, suggesting high dinoflagellate biomass. Overall, the integration of sterols with TOC, TN, C/N ratios, and land use analysis effectively reveals the spatial heterogeneity of autochthonous, allochthonous, and anthropogenic organic matter in Lake Dian sediments, providing a robust tool for eutrophication monitoring and pollution source apportionment in plateau lake systems.
Lake Dian, a typical plateau freshwater lake in China, has experienced increasingly severe eutrophication in recent years due to intensified human activities and continuous nutrient inputs. To elucidate the composition and sources of sterols in surface sediments of Lake Dian , this study conducted systematic multi-site sampling and analyzed the spatial distribution of sterol molecular markers, total organic carbon (TOC), total nitrogen (TN), and the C/N ratio, in conjunction with watershed land use patterns. The results revealed pronounced spatial heterogeneity in organic matter content and C/N ratios across the lake. The Caohai area, influenced by urban runoff and multiple river inflows, exhibited higher organic matter content and C/N values compared to Waihai, displaying a southwest-high, northeast-low gradient. In Waihai, deep central zones had greater organic matter content and C/N ratios than littoral shallow areas, forming a center-high, margin-low pattern. Sterol biomarker analysis indicated that C27 sterols (coprostanol, epicoprostanol, cholesterol, and cholestanol) were primarily enriched in Caohai and the northern and southeastern Waihai, reflecting significant inputs from domestic sewage and anthropogenic activities, C?? sterols, including coprostanol and epicoprostanol, were mainly distributed in Caohai, as well as in the northeastern and southern regions of Waihai, indicating strong influence from domestic sewage inputs. C28 and C29 sterols (campesterol, stigmasterol, and β-sitosterol) were enriched in Caohai as well as in the central and southern regions of Waihai,, indicating substantial higher plant inputs associated with intensive agricultural activity. C30 sterol (dinosterol) was notably elevated in the southern sediments, suggesting high dinoflagellate biomass. Overall, the integration of sterols with TOC, TN, C/N ratios, and land use analysis effectively reveals the spatial heterogeneity of autochthonous, allochthonous, and anthropogenic organic matter in Lake Dian sediments, providing a robust tool for eutrophication monitoring and pollution source apportionment in plateau lake systems.
Li Xingyue, Liu Xiaomin, Liu Tingxi, Zhang Sheng, Lu Zongfu, Wang Wenjuan, Wang Zihang, Yang Yaotian
2026,(3):000-000, DOI: 10.18307/2026.0311
Available online: November 03, 2025
Abstract:
Under the conditions of climate warming and water eutrophication, cyanobacteria blooms frequently broke out in Hulun Lake in 2022, covering almost the entire lake surface, destroying the water landscape and seriously threatening the health and safety of the lake ecosystem. In order to reveal the driving mechanism of large-scale outbreak of cyanobacteria in Hulun Lake, 13 sampling sites were selected to collect surface, middle and bottom water samples in spring, summer and autumn of 2022, and the species, cell density, biomass and water quality indexes of cyanobacteria were studied. The results showed that a total of 22 species of cyanobacteria were identified, and a total of 10 dominant species were identified, among which Microcystis sp. was the dominant species throughout the survey period. There were significant changes in the density and biomass of cyanobacteria in different periods and depths. The density (2.58×109 cells/L) and biomass (3.30×102 mg/L) of cyanobacteria in summer were 1~2 orders of magnitude higher than those in spring and autumn. In spring, the density and biomass of cyanobacteria were the highest in the bottom layer of the lake, and the highest in the surface layer of the lake in summer and autumn. The results of correlation analysis and redundancy analysis showed that there were seasonal differences in the influencing factors of cyanobacteria. Water temperature, nitrogen and phosphorus content, dissolved oxygen and pH were the key environmental factors affecting the occurrence of cyanobacterial blooms. In terms of control strategies, moderate control of nutrient content, implementation of nitrogen and phosphorus dual control, and improvement of cyanobacterial bloom prediction and early warning and emergency response capabilities are the fundamental ways to effectively reduce the risk of cyanobacterial blooms, which is of great significance for the prevention and control of cyanobacterial blooms in eutrophic lakes in the future.
Under the conditions of climate warming and water eutrophication, cyanobacteria blooms frequently broke out in Hulun Lake in 2022, covering almost the entire lake surface, destroying the water landscape and seriously threatening the health and safety of the lake ecosystem. In order to reveal the driving mechanism of large-scale outbreak of cyanobacteria in Hulun Lake, 13 sampling sites were selected to collect surface, middle and bottom water samples in spring, summer and autumn of 2022, and the species, cell density, biomass and water quality indexes of cyanobacteria were studied. The results showed that a total of 22 species of cyanobacteria were identified, and a total of 10 dominant species were identified, among which Microcystis sp. was the dominant species throughout the survey period. There were significant changes in the density and biomass of cyanobacteria in different periods and depths. The density (2.58×109 cells/L) and biomass (3.30×102 mg/L) of cyanobacteria in summer were 1~2 orders of magnitude higher than those in spring and autumn. In spring, the density and biomass of cyanobacteria were the highest in the bottom layer of the lake, and the highest in the surface layer of the lake in summer and autumn. The results of correlation analysis and redundancy analysis showed that there were seasonal differences in the influencing factors of cyanobacteria. Water temperature, nitrogen and phosphorus content, dissolved oxygen and pH were the key environmental factors affecting the occurrence of cyanobacterial blooms. In terms of control strategies, moderate control of nutrient content, implementation of nitrogen and phosphorus dual control, and improvement of cyanobacterial bloom prediction and early warning and emergency response capabilities are the fundamental ways to effectively reduce the risk of cyanobacterial blooms, which is of great significance for the prevention and control of cyanobacterial blooms in eutrophic lakes in the future.
2026,(3):000-000, DOI: 10.18307/2026.0316
Available online: October 31, 2025
Abstract:
Phytoplankton chlorophyll-a (Chl-a) concentration serves as a crucial indicator for assessing water eutrophication status. Conventional monitoring approaches face significant limitations: laboratory analyses are time-consuming and labor-intensive, while in-situ sensors suffer from biofouling interference, low accuracy, and high maintenance costs. Traditional satellite remote sensing techniques are unsuitable for high-precision and real-time monitoring due to incorrect atmospheric correction, technical complexity, and poor temporal resolution. The emergence of hyperspectral proximal sensing technology has effectively addressed these challenges, significantly improving Chl-a concentration monitoring efficiency. This study employed a novel portable hyperspectral proximal sensing water quality monitoring device, collecting 533 synchronized in-situ Chl-a measurements across eight lakes, reservoirs, and rivers from 2021 to 2024. High-accuracy Chl-a concentration inversion models were developed and compared through both linear regression algorithms and machine learning approaches to achieve real-time Chl-a concentration monitoring. Comparative analysis of models based on linear regression, Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM) algorithms revealed that the XGBoost-based model demonstrated superior performance (R2=0.87, RMSE=6.02 μg/L, MAE=3.98 μg/L). This innovative methodology enables simultaneous spectral acquisition and Chl-a concentration estimation, streamlining field monitoring procedures while reducing technical barriers and significantly enhancing operational efficiency.
Phytoplankton chlorophyll-a (Chl-a) concentration serves as a crucial indicator for assessing water eutrophication status. Conventional monitoring approaches face significant limitations: laboratory analyses are time-consuming and labor-intensive, while in-situ sensors suffer from biofouling interference, low accuracy, and high maintenance costs. Traditional satellite remote sensing techniques are unsuitable for high-precision and real-time monitoring due to incorrect atmospheric correction, technical complexity, and poor temporal resolution. The emergence of hyperspectral proximal sensing technology has effectively addressed these challenges, significantly improving Chl-a concentration monitoring efficiency. This study employed a novel portable hyperspectral proximal sensing water quality monitoring device, collecting 533 synchronized in-situ Chl-a measurements across eight lakes, reservoirs, and rivers from 2021 to 2024. High-accuracy Chl-a concentration inversion models were developed and compared through both linear regression algorithms and machine learning approaches to achieve real-time Chl-a concentration monitoring. Comparative analysis of models based on linear regression, Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM) algorithms revealed that the XGBoost-based model demonstrated superior performance (R2=0.87, RMSE=6.02 μg/L, MAE=3.98 μg/L). This innovative methodology enables simultaneous spectral acquisition and Chl-a concentration estimation, streamlining field monitoring procedures while reducing technical barriers and significantly enhancing operational efficiency.
wangcong, wangzhi, lienhua, zhanglu, liuxi, lishuyin, liruiwen, xingpeng, aosicheng, lushaoyong, tantiejun, yangjun
2026,(3):000-000, DOI: 10.18307/2026.0301
Available online: October 31, 2025
Abstract:
The lack of freshwater ecosystem damage assessment system seriously hinders the implementation of environmental justice and ecological compensation in China. To address this gap, we developed a comprehensive freshwater ecosystem damage assessment system, guided by national standards for ecological environment damage assessment and the practical needs of environmental protection public interest litigation. The system encompasses three dimensions, including environmental quality, biological integrity and ecological function, and is structured into 1 target, 2 sub-targets, 8 criteria, and 27 indicators. In this system, the ecological baseline of the indicators is calculated by the trisection method and the quartile method, and hierarchical calculation formulas from the indicator to the target were provided. The degree of ecosystem damage is measured by the ecological damage index (EDI), with threshold values of 1.2, 1.5, and 2.0 representing mild, moderate, and severe damage, respectively. To validate the system’s applicability, case studies were conducted on Honghu Lake and a river in Xianning. To further improve the effectiveness of the system, the sensitivity and evaluation accuracy of the criterion factors was analyzed. Ensuring evaluation accuracy, we developed a prioritized combination list of assessment criteria (R2 > 0.9, RMSE < 0.1). Subsequently, non-core indicators in the same criterions were removed through correlation analysis. Finally, a prioritized combination list of 1 to 4 levels was provided, including 8, 7, 6, and 5 criteria, respectively, covering 14 to 21 indicators. The construction and application of this freshwater ecosystem damage assessment system not only advance the development of water ecological damage assessment theory in China, but also provide robust theoretical and methodological support for ecological environment protection law enforcement and ecological compensation practices.
The lack of freshwater ecosystem damage assessment system seriously hinders the implementation of environmental justice and ecological compensation in China. To address this gap, we developed a comprehensive freshwater ecosystem damage assessment system, guided by national standards for ecological environment damage assessment and the practical needs of environmental protection public interest litigation. The system encompasses three dimensions, including environmental quality, biological integrity and ecological function, and is structured into 1 target, 2 sub-targets, 8 criteria, and 27 indicators. In this system, the ecological baseline of the indicators is calculated by the trisection method and the quartile method, and hierarchical calculation formulas from the indicator to the target were provided. The degree of ecosystem damage is measured by the ecological damage index (EDI), with threshold values of 1.2, 1.5, and 2.0 representing mild, moderate, and severe damage, respectively. To validate the system’s applicability, case studies were conducted on Honghu Lake and a river in Xianning. To further improve the effectiveness of the system, the sensitivity and evaluation accuracy of the criterion factors was analyzed. Ensuring evaluation accuracy, we developed a prioritized combination list of assessment criteria (R2 > 0.9, RMSE < 0.1). Subsequently, non-core indicators in the same criterions were removed through correlation analysis. Finally, a prioritized combination list of 1 to 4 levels was provided, including 8, 7, 6, and 5 criteria, respectively, covering 14 to 21 indicators. The construction and application of this freshwater ecosystem damage assessment system not only advance the development of water ecological damage assessment theory in China, but also provide robust theoretical and methodological support for ecological environment protection law enforcement and ecological compensation practices.
2026,(3):000-000, DOI: 10.18307/2026.0334
Available online: October 31, 2025
Abstract:
Rapid and accurate monitoring of aquatic vegetation is crucial for the protection and management of lake ecosystems. In this study, the Nanji Wetland National Nature Reserve and Poyang Lake National Nature Reserve were selected as study areas.First,the Normalized Difference Vegetation Index(NDVI) was used to separate water bodies,Then, the Normalized Difference Mud Index(NDMI) was constructed to eliminate the interfernce of mudflats on vegetation classification.Next,floating-leaved plants and emergent plants are distinguished based on differences in the backscattering coefficient within the radar imagery.Finally, this study compared the proposed method with existing methods for distinguishing these two types of aquatic vegetation. The results show that:(1) The method based on backscattering coefficients for distinguishing floating-leaved plants from emergent plants achieved a significant improvement in overall accuracy compared to existing methods. The overall classification accuracy of this method was 89.72%, with a Kappa coefficient of 0.8413.(2) For remote sensing images from different periods, the overall classification accuracy of our method was consistently above 80%, demonstrating good stability and reliability.(3) Our method effectively excluded the interference of mudflats on vegetation classification, thereby avoiding the misclassification of exposed mudflats after water recession. It is particularly suitable for floodplain wetlands with large water level fluctuations.In summary,the method developed in this study provides a new technical approach for distinguishing between floating-leaved and emergent plants and offers a reference for monitoring different types of aquatic vegetation.
Rapid and accurate monitoring of aquatic vegetation is crucial for the protection and management of lake ecosystems. In this study, the Nanji Wetland National Nature Reserve and Poyang Lake National Nature Reserve were selected as study areas.First,the Normalized Difference Vegetation Index(NDVI) was used to separate water bodies,Then, the Normalized Difference Mud Index(NDMI) was constructed to eliminate the interfernce of mudflats on vegetation classification.Next,floating-leaved plants and emergent plants are distinguished based on differences in the backscattering coefficient within the radar imagery.Finally, this study compared the proposed method with existing methods for distinguishing these two types of aquatic vegetation. The results show that:(1) The method based on backscattering coefficients for distinguishing floating-leaved plants from emergent plants achieved a significant improvement in overall accuracy compared to existing methods. The overall classification accuracy of this method was 89.72%, with a Kappa coefficient of 0.8413.(2) For remote sensing images from different periods, the overall classification accuracy of our method was consistently above 80%, demonstrating good stability and reliability.(3) Our method effectively excluded the interference of mudflats on vegetation classification, thereby avoiding the misclassification of exposed mudflats after water recession. It is particularly suitable for floodplain wetlands with large water level fluctuations.In summary,the method developed in this study provides a new technical approach for distinguishing between floating-leaved and emergent plants and offers a reference for monitoring different types of aquatic vegetation.
2026,(3):000-000, DOI: 10.18307/2026.0325
Available online: October 31, 2025
Abstract:
Research on carbon dynamics and source processes in terminal lakes contributes to a precise characterization of their role as "sources" or "sinks" in the regional carbon cycle. This study selected Lake Ulansuhai, a terminal lake in northern China, as the research object. Using methods such as the Bayesian mixing model (MixSIAR) and a carbon isotope two-end-member mixing model, the sources of different forms of carbon in the water body and their main influencing factors were investigated. The main results are as follows: Both dissolved organic carbon (DOC) and particulate organic carbon (POC) showed a spatially decreasing concentration trend from north to south (p<0.05). In April, the primary source of both DOC and POC was phytoplankton, whereas in July and October, the main source was irrigation return flow. For DOC, the overall source contribution proportions were irrigation return flow (72%) > phytoplankton (15%) > terrestrial C3 plants (7%) > aquatic plants (6%). For POC, the overall proportions were phytoplankton (39%) > irrigation return flow (34%) > aquatic plants (15%) > terrestrial C3 plants (12%). Spatially, no significant differences were found for dissolved inorganic carbon (DIC) and particulate inorganic carbon (PIC) (p>0.05). The sources of DIC varied significantly across months: in April, it was primarily contributed by soil organic matter (92.7%) and atmospheric exchange (7.3%); in July, the main sources were irrigation return flow (74.1%) and biological activity (25.9%); in October, the main sources were irrigation return flow (71.9%) and atmospheric exchange (28.1%). PIC mainly originated from endogenous autogenic precipitation. Multiple regression analysis indicated that Chl-a and TN are the main drivers of DOC concentration (R2=0.662, p<0.001); SD, TN, and SPM collectively explained the variation in POC concentration (R2=0.566, p<0.05); NH4+-N is the core regulating factor for DIC concentration (R2=0.370, p<0.001); and both TN and pH have a dual promoting effect on PIC formation (R2=0.573, p<0.05). The findings of this study can provide a scientific basis for carbon cycle research in terminal lakes within agricultural irrigation areas.
Research on carbon dynamics and source processes in terminal lakes contributes to a precise characterization of their role as "sources" or "sinks" in the regional carbon cycle. This study selected Lake Ulansuhai, a terminal lake in northern China, as the research object. Using methods such as the Bayesian mixing model (MixSIAR) and a carbon isotope two-end-member mixing model, the sources of different forms of carbon in the water body and their main influencing factors were investigated. The main results are as follows: Both dissolved organic carbon (DOC) and particulate organic carbon (POC) showed a spatially decreasing concentration trend from north to south (p<0.05). In April, the primary source of both DOC and POC was phytoplankton, whereas in July and October, the main source was irrigation return flow. For DOC, the overall source contribution proportions were irrigation return flow (72%) > phytoplankton (15%) > terrestrial C3 plants (7%) > aquatic plants (6%). For POC, the overall proportions were phytoplankton (39%) > irrigation return flow (34%) > aquatic plants (15%) > terrestrial C3 plants (12%). Spatially, no significant differences were found for dissolved inorganic carbon (DIC) and particulate inorganic carbon (PIC) (p>0.05). The sources of DIC varied significantly across months: in April, it was primarily contributed by soil organic matter (92.7%) and atmospheric exchange (7.3%); in July, the main sources were irrigation return flow (74.1%) and biological activity (25.9%); in October, the main sources were irrigation return flow (71.9%) and atmospheric exchange (28.1%). PIC mainly originated from endogenous autogenic precipitation. Multiple regression analysis indicated that Chl-a and TN are the main drivers of DOC concentration (R2=0.662, p<0.001); SD, TN, and SPM collectively explained the variation in POC concentration (R2=0.566, p<0.05); NH4+-N is the core regulating factor for DIC concentration (R2=0.370, p<0.001); and both TN and pH have a dual promoting effect on PIC formation (R2=0.573, p<0.05). The findings of this study can provide a scientific basis for carbon cycle research in terminal lakes within agricultural irrigation areas.
2026,(3):000-000, DOI: 10.18307/2026.0331
Available online: October 29, 2025
Abstract:
Comprehensive acquisition of aquatic organism data is fundamental for the effective conservation and restoration of aquatic ecosystems. However, efficient monitoring of aquatic biodiversity dynamics in large river systems remains highly challenging. Environmental DNA (eDNA) technology, as an emerging monitoring approach, offers advantages of rapidity and high efficiency. Nevertheless, conventional cross-sectional small-volume eDNA sampling methods exhibit clear limitations in detecting rare fish species. To address this issue, the present study developed a novel mobile large-volume eDNA sampling method, which substantially increases the water volume filtered per sample through the use of capsule filtration and integrates a mobile sampling strategy to improve the efficiency and representativeness of eDNA metabarcoding surveys. In October 2022, comparative surveys were conducted at two representative cross-sections of the lower Yangtze River to evaluate differences in fish diversity detection between the mobile large-volume method and the conventional small-volume cross-sectional method. All eDNA samples were amplified and sequenced using the Tele02 primer set. The results demonstrated that: (1) Each large-volume mobile sample detected an average of 38 fish species, representing a 216.7% increase compared with the small-volume cross-sectional method (12 species); (2) The mobile large-volume method exhibited higher accuracy in biodiversity detection and greater consistency among parallel replicates; (3) The mobile large-volume sampling method detected 24 fish species of primary concern, including rare and endangered species listed in the IUCN Red List of Threatened Species, fish species listed in the Catalogue of National Key Protected Economic Aquatic Animals and Plants of China, and Chinese endemic species. This represents a 50% increase compared with the 16 species detected by the cross-sectional small-volume sampling method, with 14 species shared between the two approaches. Overall, the study confirms that the mobile large-volume eDNA sampling method demonstrates significant advantages in species detection rate, detection precision and stability, and the identification of fish species of primary conservation concern in large river systems.
Comprehensive acquisition of aquatic organism data is fundamental for the effective conservation and restoration of aquatic ecosystems. However, efficient monitoring of aquatic biodiversity dynamics in large river systems remains highly challenging. Environmental DNA (eDNA) technology, as an emerging monitoring approach, offers advantages of rapidity and high efficiency. Nevertheless, conventional cross-sectional small-volume eDNA sampling methods exhibit clear limitations in detecting rare fish species. To address this issue, the present study developed a novel mobile large-volume eDNA sampling method, which substantially increases the water volume filtered per sample through the use of capsule filtration and integrates a mobile sampling strategy to improve the efficiency and representativeness of eDNA metabarcoding surveys. In October 2022, comparative surveys were conducted at two representative cross-sections of the lower Yangtze River to evaluate differences in fish diversity detection between the mobile large-volume method and the conventional small-volume cross-sectional method. All eDNA samples were amplified and sequenced using the Tele02 primer set. The results demonstrated that: (1) Each large-volume mobile sample detected an average of 38 fish species, representing a 216.7% increase compared with the small-volume cross-sectional method (12 species); (2) The mobile large-volume method exhibited higher accuracy in biodiversity detection and greater consistency among parallel replicates; (3) The mobile large-volume sampling method detected 24 fish species of primary concern, including rare and endangered species listed in the IUCN Red List of Threatened Species, fish species listed in the Catalogue of National Key Protected Economic Aquatic Animals and Plants of China, and Chinese endemic species. This represents a 50% increase compared with the 16 species detected by the cross-sectional small-volume sampling method, with 14 species shared between the two approaches. Overall, the study confirms that the mobile large-volume eDNA sampling method demonstrates significant advantages in species detection rate, detection precision and stability, and the identification of fish species of primary conservation concern in large river systems.
2026,(3):000-000, DOI: 10.18307/2026.0315
Available online: October 22, 2025
Abstract:
Carbon sinks of natural ecological systems are regarded as one of the key pathways to combat climate change. Eutrophic lakes, due to their higher primary productivity, have higher carbon sink potential. This study estimated the algae-derived carbon sink in eutrophic Lake Taihu from 2011 to 2020 using the Vertically Generalized Production Model (VGPM), quantified the contribution of key influencing factors using the Generalized Additive Model (GAM), and conducted short-term prediction using the Autoregressive Integrated Moving Average model (ARIMA). The results indicated that, the cumulative algae-derived carbon sink in Lake Taihu reached 3.8 × 106 t from 2011 to 2020, exhibiting remarkable spatiotemporal heterogeneity. The highest carbon sink occurred in 2019 (7.2 × 105 t), and the lowest was in 2011 (1.7 × 105 t); Zhushan Bay had the highest carbon sink (291 g/m2), while Xuhu Bay had the lowest (66 g/m2). Chlorophyll a concentration was identified as the primary factor driving algal-derived carbon sink, accounting for the largest contribution (86.0%), followed by photosynthetically active radiation, suspended matter concentration, and water temperature, with contributions of 13.2%, 4.6%, and 39.3%, respectively. Using only chlorophyll a concentration as a single parameter, the ARIMA model can effectively estimate the algal-derived carbon sink in Lake Taihu. The findings provide important theoretical insights and methodological support for carbon sink assessment in eutrophic lakes. Keywords: Eutrophication, Lake, Algae, Carbon sink, Short-term prediction
Carbon sinks of natural ecological systems are regarded as one of the key pathways to combat climate change. Eutrophic lakes, due to their higher primary productivity, have higher carbon sink potential. This study estimated the algae-derived carbon sink in eutrophic Lake Taihu from 2011 to 2020 using the Vertically Generalized Production Model (VGPM), quantified the contribution of key influencing factors using the Generalized Additive Model (GAM), and conducted short-term prediction using the Autoregressive Integrated Moving Average model (ARIMA). The results indicated that, the cumulative algae-derived carbon sink in Lake Taihu reached 3.8 × 106 t from 2011 to 2020, exhibiting remarkable spatiotemporal heterogeneity. The highest carbon sink occurred in 2019 (7.2 × 105 t), and the lowest was in 2011 (1.7 × 105 t); Zhushan Bay had the highest carbon sink (291 g/m2), while Xuhu Bay had the lowest (66 g/m2). Chlorophyll a concentration was identified as the primary factor driving algal-derived carbon sink, accounting for the largest contribution (86.0%), followed by photosynthetically active radiation, suspended matter concentration, and water temperature, with contributions of 13.2%, 4.6%, and 39.3%, respectively. Using only chlorophyll a concentration as a single parameter, the ARIMA model can effectively estimate the algal-derived carbon sink in Lake Taihu. The findings provide important theoretical insights and methodological support for carbon sink assessment in eutrophic lakes. Keywords: Eutrophication, Lake, Algae, Carbon sink, Short-term prediction
2026,(1):000-000, DOI: 10.18307/2026.0100
Available online: October 22, 2025
Abstract:
Lakes and reservoirs (collectively referred to as lake-reservoirs) serve as the "power source" for the green and high-quality development of the Yangtze River Economic Belt. They also act as the "cornerstone" for ensuring the safety of drinking water in cities along the Yangtze River Economic Belt and in the Beijing-Tianjin-Hebei-Henan region. Clarifying the spatial distribution and water quality evolution of lake-reservoirs used as drinking water sources is helpful to enhance the capacity to safeguard drinking water security. This study integrates ecological and environmental statistical information to construct a dataset of prefecture-level and county-level centralized drinking water sources across 11 provinces along the Yangtze River Economic Belt. Our results show that among all 1,557 prefecture-level and county-level centralized drinking water sources in 2025, 762 water sources are lake-reservoir types accounting for 49.0%, which distributed across 23 lakes and 682 reservoirs. Over the past decade, there has been a notable increase in both the number and proportion of lake-reservoir-type drinking water sources at both prefecture-level and county-level centralized drinking water sources, which further highlights the crucial role of lakes and reservoirs in ensuring the safety of urban drinking water. Long-term Landsat satellite remote sensing estimation results indicate that since 1986, the transparency of lakes and reservoirs used as drinking water sources in the Yangtze River Economic Belt has shown a significant upward trend. Secchi disk depth of lakes and reservoirs increased from 1.41 ± 0.78 m in 1986 to 1.94 ± 1.35 m in 2024 demonstrating that the overall water bodies are becoming clearer. However, there are marked differences between lakes and reservoirs, with lake transparency declining while reservoir transparency has risen significantly. Long-term positioning monitoring of five key water quality indicators—dissolved oxygen, total nitrogen, ammonia nitrogen, total phosphorus, and biochemical oxygen demand—in 47 drinking water source lakes and reservoirs from 2005 to 2024 uncovers an overall significant improvement in water quality. The total nitrogen and total phosphorus concentrations decreased from 1.90 mg/L and 0.100 mg/L in 2005 to 1.30 mg/L and 0.052 mg/L in 2024, respectively. Nevertheless, the total nitrogen concentration in reservoirs has not shown marked improvement and has even increased in some cases. Currently, the protection, governance, and sustainable development of drinking water source lakes and reservoirs continue to face multiple risks and challenges, including excessive external pollution loadings from the catchment and increased internal pollution release, high nitrogen and phosphorus concentrations leading to blue-green algae blooms, the degradation of submerged vegetation and decline in biodiversity, as well as the increased frequency of extreme floods and droughts caused by global climate change.
Lakes and reservoirs (collectively referred to as lake-reservoirs) serve as the "power source" for the green and high-quality development of the Yangtze River Economic Belt. They also act as the "cornerstone" for ensuring the safety of drinking water in cities along the Yangtze River Economic Belt and in the Beijing-Tianjin-Hebei-Henan region. Clarifying the spatial distribution and water quality evolution of lake-reservoirs used as drinking water sources is helpful to enhance the capacity to safeguard drinking water security. This study integrates ecological and environmental statistical information to construct a dataset of prefecture-level and county-level centralized drinking water sources across 11 provinces along the Yangtze River Economic Belt. Our results show that among all 1,557 prefecture-level and county-level centralized drinking water sources in 2025, 762 water sources are lake-reservoir types accounting for 49.0%, which distributed across 23 lakes and 682 reservoirs. Over the past decade, there has been a notable increase in both the number and proportion of lake-reservoir-type drinking water sources at both prefecture-level and county-level centralized drinking water sources, which further highlights the crucial role of lakes and reservoirs in ensuring the safety of urban drinking water. Long-term Landsat satellite remote sensing estimation results indicate that since 1986, the transparency of lakes and reservoirs used as drinking water sources in the Yangtze River Economic Belt has shown a significant upward trend. Secchi disk depth of lakes and reservoirs increased from 1.41 ± 0.78 m in 1986 to 1.94 ± 1.35 m in 2024 demonstrating that the overall water bodies are becoming clearer. However, there are marked differences between lakes and reservoirs, with lake transparency declining while reservoir transparency has risen significantly. Long-term positioning monitoring of five key water quality indicators—dissolved oxygen, total nitrogen, ammonia nitrogen, total phosphorus, and biochemical oxygen demand—in 47 drinking water source lakes and reservoirs from 2005 to 2024 uncovers an overall significant improvement in water quality. The total nitrogen and total phosphorus concentrations decreased from 1.90 mg/L and 0.100 mg/L in 2005 to 1.30 mg/L and 0.052 mg/L in 2024, respectively. Nevertheless, the total nitrogen concentration in reservoirs has not shown marked improvement and has even increased in some cases. Currently, the protection, governance, and sustainable development of drinking water source lakes and reservoirs continue to face multiple risks and challenges, including excessive external pollution loadings from the catchment and increased internal pollution release, high nitrogen and phosphorus concentrations leading to blue-green algae blooms, the degradation of submerged vegetation and decline in biodiversity, as well as the increased frequency of extreme floods and droughts caused by global climate change.
2026,(1):000-000, DOI: 10.18307/2026.0103
Available online: October 16, 2025
Abstract:
Inland aquatic systems play a critical role in the global carbon cycle, with carbon dioxide (CO2) emission characteristics directly influencing climate change dynamics. However, current research on CO2 emissions from inland waters predominantly focuses on local scales, lacking systematic cross-regional and global integration. This gap introduces substantial uncertainties in global CO2 flux estimates and constrains comprehensive understanding of spatiotemporal patterns and driving mechanisms of aquatic carbon fluxes. Through systematic review of primary monitoring methods (floating chambers method, eddy covariance method, boundary layer method) and upscaling approaches (area-based extrapolation, statistical regression, mechanistic process modeling) for inland water CO2 fluxes, this study reveals how methodological differences drive data uncertainties. firstly, the differences in the characteristics of the three monitoring methods and the observational biases caused by the differences in the applicable scenarios are comparatively analysed; then, the sources of estimation bias of different upscaling methods are analysed, including the neglect of environmental heterogeneity in the area extrapolation method, the insufficient representativeness of the driving factors in the statistical regression method, and the simplification of boundary conditions in the mechanistic process model. The research demonstrates that enhanced data quality and precision are fundamental to improving estimation accuracy. Future studies should advance automated monitoring technologies, strengthen spatiotemporal data representativeness, integrate abiotic-biotic factor interactions, and optimize model frameworks to refine carbon source/sink assessments and provide robust scientific support for global carbon mitigation strategies.
Inland aquatic systems play a critical role in the global carbon cycle, with carbon dioxide (CO2) emission characteristics directly influencing climate change dynamics. However, current research on CO2 emissions from inland waters predominantly focuses on local scales, lacking systematic cross-regional and global integration. This gap introduces substantial uncertainties in global CO2 flux estimates and constrains comprehensive understanding of spatiotemporal patterns and driving mechanisms of aquatic carbon fluxes. Through systematic review of primary monitoring methods (floating chambers method, eddy covariance method, boundary layer method) and upscaling approaches (area-based extrapolation, statistical regression, mechanistic process modeling) for inland water CO2 fluxes, this study reveals how methodological differences drive data uncertainties. firstly, the differences in the characteristics of the three monitoring methods and the observational biases caused by the differences in the applicable scenarios are comparatively analysed; then, the sources of estimation bias of different upscaling methods are analysed, including the neglect of environmental heterogeneity in the area extrapolation method, the insufficient representativeness of the driving factors in the statistical regression method, and the simplification of boundary conditions in the mechanistic process model. The research demonstrates that enhanced data quality and precision are fundamental to improving estimation accuracy. Future studies should advance automated monitoring technologies, strengthen spatiotemporal data representativeness, integrate abiotic-biotic factor interactions, and optimize model frameworks to refine carbon source/sink assessments and provide robust scientific support for global carbon mitigation strategies.
2026,(2):000-000, DOI: 10.18307/2026.0210
Available online: October 10, 2025
Abstract:
The remote sensing retrieval of algal blooms in river systems is often interfered by the boundary effects of riparian wetlands, leading to limited accuracy with traditional methods in narrow water bodies. The tail-end section of the Ganjiang River, as a typical sensitive water area, has an unclear mechanism for algal bloom outbreaks. This study proposes an improved algorithm integrating the inward masking technique, coupling the Phytoplankton Absorption Index (FAI) with the Otsu method, effectively suppressing near-shore interference. Based on Sentinel-2/Landsat satellite data from 2019 to 2024, this study accurately extracts algal blooms in the tail-end section of the Ganjiang River. By combining remote sensing retrieval results with hydrological and meteorological data, the temporal and spatial distribution characteristics and outbreak mechanisms of algal blooms in this region were analyzed. The results indicate: (1) From 2019 to 2024, the scale of algal blooms showed an increasing trend with significant seasonality, peaking in late summer and early autumn (August and September), predominantly characterized by small-scale blooms. (2) Spatially, algal blooms were significantly concentrated in the near-shore slow-flow areas of the southern and middle branches of the Ganjiang River. The high-temperature heatwave weather during the late summer and early autumn low-flow period is the primary driving factor for the large-scale outbreak of algal blooms in this region.
The remote sensing retrieval of algal blooms in river systems is often interfered by the boundary effects of riparian wetlands, leading to limited accuracy with traditional methods in narrow water bodies. The tail-end section of the Ganjiang River, as a typical sensitive water area, has an unclear mechanism for algal bloom outbreaks. This study proposes an improved algorithm integrating the inward masking technique, coupling the Phytoplankton Absorption Index (FAI) with the Otsu method, effectively suppressing near-shore interference. Based on Sentinel-2/Landsat satellite data from 2019 to 2024, this study accurately extracts algal blooms in the tail-end section of the Ganjiang River. By combining remote sensing retrieval results with hydrological and meteorological data, the temporal and spatial distribution characteristics and outbreak mechanisms of algal blooms in this region were analyzed. The results indicate: (1) From 2019 to 2024, the scale of algal blooms showed an increasing trend with significant seasonality, peaking in late summer and early autumn (August and September), predominantly characterized by small-scale blooms. (2) Spatially, algal blooms were significantly concentrated in the near-shore slow-flow areas of the southern and middle branches of the Ganjiang River. The high-temperature heatwave weather during the late summer and early autumn low-flow period is the primary driving factor for the large-scale outbreak of algal blooms in this region.
2026,(2):000-000, DOI: 10.18307/2026.0244
Available online: September 24, 2025
Abstract:
Located in the arid semi-arid transition zone at the edge of the East Asian monsoon, the Huangqihai Lake is a typical lake ecosystem that is highly sensitive to climate change and human activities. Clarifying the differences between climate-driven natural evolutionary processes and human-induced ecological changes is a key scientific issue for understanding the response mechanisms of lake ecosystems in this region. In this study, the historical evolution of phytoplankton primary productivity and lake trophic state over the past ~1600 years was inferred in the Huangqihai Lake based on visible reflectance spectroscopy (VRS)-reconstructed chlorophyll a (Chl.a) concentration in sediments and visible-near-infrared spectroscopy (VNIR)-reconstructed total organic carbon (TOC) concentration in lake water. Combined with multi-environmental proxies such as TOC, total nitrogen (TN), total phosphorus (TP), particle size, magnetic susceptibility and geochemical elements in sediments, the evolution of the Huangqihai Lake ecosystem and its main drivers were systematically explored. The results show that before ~820 AD, despite the warm and humid climate and the enhanced East Asian summer monsoon, the runoff from the watershed led to a decrease in the light penetration of lake water, which suppressed the primary productivity of the lake. Between 820 and 1500 AD, the warm and humid climate promoted the vegetation development in the watershed, leading to increased nutrient input into the lake. This nutrient enrichment likely exceeded ecological thresholds, significantly enhancing phytoplankton productivity and TOC concentrations in the lake water. These changes contributed to pronounced shifts in lake ecosystem structure. Since 1500 AD, despite a shift to a cooler and drier climate, intensified agricultural activities in the watershed led to increased soil erosion and nutrient input, maintaining relatively stable algal productivity. In the 20th century, a combination of climate warming, enhanced evaporation, and increased anthropogenic disturbances such as over-exploitation of groundwater and exploitation of lake resources, resulted in a marked decline in lake water levels and algal productivity, indicating a trend of ecosystem degradation. This study reveals the nonlinear and phased evolution of the Huangqihai Lake ecosystem under the combined effects of climate change and human activities, highlighting the profound impacts of land use, groundwater regulation, and hydrological processes on the stability of lake systems in arid and semi-arid regions. These findings provide a scientific basis for ecosystem restoration and adaptive management of water resources in these regions.
Located in the arid semi-arid transition zone at the edge of the East Asian monsoon, the Huangqihai Lake is a typical lake ecosystem that is highly sensitive to climate change and human activities. Clarifying the differences between climate-driven natural evolutionary processes and human-induced ecological changes is a key scientific issue for understanding the response mechanisms of lake ecosystems in this region. In this study, the historical evolution of phytoplankton primary productivity and lake trophic state over the past ~1600 years was inferred in the Huangqihai Lake based on visible reflectance spectroscopy (VRS)-reconstructed chlorophyll a (Chl.a) concentration in sediments and visible-near-infrared spectroscopy (VNIR)-reconstructed total organic carbon (TOC) concentration in lake water. Combined with multi-environmental proxies such as TOC, total nitrogen (TN), total phosphorus (TP), particle size, magnetic susceptibility and geochemical elements in sediments, the evolution of the Huangqihai Lake ecosystem and its main drivers were systematically explored. The results show that before ~820 AD, despite the warm and humid climate and the enhanced East Asian summer monsoon, the runoff from the watershed led to a decrease in the light penetration of lake water, which suppressed the primary productivity of the lake. Between 820 and 1500 AD, the warm and humid climate promoted the vegetation development in the watershed, leading to increased nutrient input into the lake. This nutrient enrichment likely exceeded ecological thresholds, significantly enhancing phytoplankton productivity and TOC concentrations in the lake water. These changes contributed to pronounced shifts in lake ecosystem structure. Since 1500 AD, despite a shift to a cooler and drier climate, intensified agricultural activities in the watershed led to increased soil erosion and nutrient input, maintaining relatively stable algal productivity. In the 20th century, a combination of climate warming, enhanced evaporation, and increased anthropogenic disturbances such as over-exploitation of groundwater and exploitation of lake resources, resulted in a marked decline in lake water levels and algal productivity, indicating a trend of ecosystem degradation. This study reveals the nonlinear and phased evolution of the Huangqihai Lake ecosystem under the combined effects of climate change and human activities, highlighting the profound impacts of land use, groundwater regulation, and hydrological processes on the stability of lake systems in arid and semi-arid regions. These findings provide a scientific basis for ecosystem restoration and adaptive management of water resources in these regions.
2026,(2):000-000, DOI: 10.18307/2026.0216
Available online: September 24, 2025
Abstract:
Microorganisms respond rapidly to environmental changes, making them promising indicators for ecological assessments. However, their application in assessing aquatic ecosystems remains limited. This study investigated bacterial community structure in both water and sediments across three typologically different lake areas of Poyang Lake—specifically, the main lake area, dish-shaped lakes, and aquaculture lakes—using high-throughput sequencing techniques. A machine learning approach was employed to develop a Microbial Biotic Index (MBI) for assessing the ecological status of these lakes. The results revealed significant disparities in nutrient levels of water and sediment between different types of lake zones, which drove the spatial variations of bacterial community structures and dominant genera. Although community coalescence between water and sediment bacterial communities was limited, higher trophic state index (TSI) levels were associated with increased cross-habitat connectivity, as evidenced by a significantly greater proportion of sediment-derived bacteria in the water column. Using quantile regression and machine learning, we classified ASVs from water and sediment into five ecological groups. The resulting MBI showed a high degree of agreement with trophic state indices for both water and sediment. The ecological assessment based on the MBI indicated that water quality in the main lake and aquaculture lakes was better than in the dish-shaped lakes. Sediment ecological conditions ranked highest in aquaculture lakes, followed by dish-shaped lakes, and lowest in the main lake area. Overall, water quality was better than sediment conditions, suggesting that sediments may serve as internal sources of eutrophication. These findings underscore the importance of incorporating sediment condition monitoring into future lake health management. This study proposed a novel microbiome-based assessment index constructed using machine learning, offering a robust tool for evaluating aquatic ecological conditions under varying trophic states.
Microorganisms respond rapidly to environmental changes, making them promising indicators for ecological assessments. However, their application in assessing aquatic ecosystems remains limited. This study investigated bacterial community structure in both water and sediments across three typologically different lake areas of Poyang Lake—specifically, the main lake area, dish-shaped lakes, and aquaculture lakes—using high-throughput sequencing techniques. A machine learning approach was employed to develop a Microbial Biotic Index (MBI) for assessing the ecological status of these lakes. The results revealed significant disparities in nutrient levels of water and sediment between different types of lake zones, which drove the spatial variations of bacterial community structures and dominant genera. Although community coalescence between water and sediment bacterial communities was limited, higher trophic state index (TSI) levels were associated with increased cross-habitat connectivity, as evidenced by a significantly greater proportion of sediment-derived bacteria in the water column. Using quantile regression and machine learning, we classified ASVs from water and sediment into five ecological groups. The resulting MBI showed a high degree of agreement with trophic state indices for both water and sediment. The ecological assessment based on the MBI indicated that water quality in the main lake and aquaculture lakes was better than in the dish-shaped lakes. Sediment ecological conditions ranked highest in aquaculture lakes, followed by dish-shaped lakes, and lowest in the main lake area. Overall, water quality was better than sediment conditions, suggesting that sediments may serve as internal sources of eutrophication. These findings underscore the importance of incorporating sediment condition monitoring into future lake health management. This study proposed a novel microbiome-based assessment index constructed using machine learning, offering a robust tool for evaluating aquatic ecological conditions under varying trophic states.
2026,(2):000-000, DOI: 10.18307/2026.0215
Available online: September 22, 2025
Abstract:
Under the dual pressures of global climate change and anthropogenic activities, significant shifts have been observed in the succession characteristics of lake biological communities and ecosystem structures, with diatoms emerging as one of the key indicators for assessing lake environmental changes. This study focuses on Chenghai Lake, a natural closed deep-water lake, investigating seasonal patterns in water environment, diatom community structure, and biodiversity through bi-monthly stratified sampling at four open-water stations over one year. The research evaluates the driving roles of key factors such as lake water alkalinity, eutrophication levels, and water temperature. Hydrochemical results reveal that Chenghai Lake is currently a phosphorus-limited system, with water pH consistently exceeding 9 annually and peaking in winter. Chlorophyll-a (Chl-a) and dissolved oxygen (DO) exhibit seasonal dynamics synchronous with pH fluctuations. 122 diatom species belonging to 21 genera were identified. The diatom community demonstrates a seasonal adaptive strategy of functional group shift between planktonic and benthic forms, alongside high spatial homogeneity in distribution. Seasonal differences in community structure were significant: planktonic species dominated from January to May, benthic/epiphytic species prevailed from July to September, and both groups co-dominated in November. Spatially, dominant species and their relative abundances remained consistent across sampling sites. Redundancy analysis (RDA) revealed that water temperature (~31%) is the primary environmental driver of seasonal shifts in dominant diatom species, with environmental gradients including conductivity (13.7%) and nutrients (6.1%) synergistically facilitating seasonal succession. Meanwhile, seasonal variation in thermal stratification intensity of deep lakes might influence algal growth by regulating water mixing intensity. Diatom species richness decreased with increasing water depth and exhibited significant seasonal differences (with the highest diversity in summer and autumn). Spatially, diatom diversity showed no significant differences among sampling sites due to convergent aquatic environmental conditions. The spatiotemporal variation in diatom diversity was significantly influenced by interactive effects of multiple environmental factors including temperature, water depth, and nutrients. This study provides targeted scientific insights for ecosystem evaluation and biodiversity conservation in closed lakes, offering data support for the effective protection of low-latitude plateau deep-water lakes under future climate change scenarios.
Under the dual pressures of global climate change and anthropogenic activities, significant shifts have been observed in the succession characteristics of lake biological communities and ecosystem structures, with diatoms emerging as one of the key indicators for assessing lake environmental changes. This study focuses on Chenghai Lake, a natural closed deep-water lake, investigating seasonal patterns in water environment, diatom community structure, and biodiversity through bi-monthly stratified sampling at four open-water stations over one year. The research evaluates the driving roles of key factors such as lake water alkalinity, eutrophication levels, and water temperature. Hydrochemical results reveal that Chenghai Lake is currently a phosphorus-limited system, with water pH consistently exceeding 9 annually and peaking in winter. Chlorophyll-a (Chl-a) and dissolved oxygen (DO) exhibit seasonal dynamics synchronous with pH fluctuations. 122 diatom species belonging to 21 genera were identified. The diatom community demonstrates a seasonal adaptive strategy of functional group shift between planktonic and benthic forms, alongside high spatial homogeneity in distribution. Seasonal differences in community structure were significant: planktonic species dominated from January to May, benthic/epiphytic species prevailed from July to September, and both groups co-dominated in November. Spatially, dominant species and their relative abundances remained consistent across sampling sites. Redundancy analysis (RDA) revealed that water temperature (~31%) is the primary environmental driver of seasonal shifts in dominant diatom species, with environmental gradients including conductivity (13.7%) and nutrients (6.1%) synergistically facilitating seasonal succession. Meanwhile, seasonal variation in thermal stratification intensity of deep lakes might influence algal growth by regulating water mixing intensity. Diatom species richness decreased with increasing water depth and exhibited significant seasonal differences (with the highest diversity in summer and autumn). Spatially, diatom diversity showed no significant differences among sampling sites due to convergent aquatic environmental conditions. The spatiotemporal variation in diatom diversity was significantly influenced by interactive effects of multiple environmental factors including temperature, water depth, and nutrients. This study provides targeted scientific insights for ecosystem evaluation and biodiversity conservation in closed lakes, offering data support for the effective protection of low-latitude plateau deep-water lakes under future climate change scenarios.
2026,(2):000-000, DOI: 10.18307/2026.0252
Available online: September 22, 2025
Abstract:
Various factors such as Dam discharge, algal photosynthesis, and sudden increase in water temperature in the natural environment can lead to supersaturation of Dissolved Oxygen (DO) or Total Dissolved Gas (TDG), which may cause fish to suffer from gas bubble disease or even death. In order to investigate the quantitative effect of algal photosynthesis alone on dissolved gas, especially TDG supersaturation, this paper carried out a quantitative study of the effect of algal photosynthesis on dissolved gas supersaturation in the Xiangjiaba reservoir area using the light-dark bottle method. Additionally, the relationship between dissolved gas saturation and algal density was analyzed in the downstream section of Jinsha River, considering the combined effect of dam release and algal photosynthesis and oxygen production. The results showed that: the increase of TDG saturation due to algal oxygen production ranged from 0.18% to 5.67%, significantly lower than the effect of the spillway building on TDG saturation. The effect of algal photosynthesis on dissolved gases was highly dependent on hydrodynamic factors. In tributaries, DO and TDG saturation exhibited a significant positive correlation with the algal density, whereas this relationship was negligible in the main channel. Algal photosynthesis had a more pronounced influence on DO saturation than on TDG saturation. The effect of algal photosynthesis on DO saturation was greater than that on TDG saturation, and the prototype observations at consecutive times showed that the variation of TDG saturation was much smaller than that of DO saturation. These findings provide a basis for clarifying the key drivers of dissolved gas supersaturation in reservoirs, and offer theoretical insights for mitigating the effects of dissolved gas supersaturation on fish.
Various factors such as Dam discharge, algal photosynthesis, and sudden increase in water temperature in the natural environment can lead to supersaturation of Dissolved Oxygen (DO) or Total Dissolved Gas (TDG), which may cause fish to suffer from gas bubble disease or even death. In order to investigate the quantitative effect of algal photosynthesis alone on dissolved gas, especially TDG supersaturation, this paper carried out a quantitative study of the effect of algal photosynthesis on dissolved gas supersaturation in the Xiangjiaba reservoir area using the light-dark bottle method. Additionally, the relationship between dissolved gas saturation and algal density was analyzed in the downstream section of Jinsha River, considering the combined effect of dam release and algal photosynthesis and oxygen production. The results showed that: the increase of TDG saturation due to algal oxygen production ranged from 0.18% to 5.67%, significantly lower than the effect of the spillway building on TDG saturation. The effect of algal photosynthesis on dissolved gases was highly dependent on hydrodynamic factors. In tributaries, DO and TDG saturation exhibited a significant positive correlation with the algal density, whereas this relationship was negligible in the main channel. Algal photosynthesis had a more pronounced influence on DO saturation than on TDG saturation. The effect of algal photosynthesis on DO saturation was greater than that on TDG saturation, and the prototype observations at consecutive times showed that the variation of TDG saturation was much smaller than that of DO saturation. These findings provide a basis for clarifying the key drivers of dissolved gas supersaturation in reservoirs, and offer theoretical insights for mitigating the effects of dissolved gas supersaturation on fish.
2026,(2):000-000, DOI: 10.18307/2026.0224
Available online: September 22, 2025
Abstract:
Matrix bound phosphine (MBP) in sediment is a widely existing yet often overlooked biologically available phosphorus pool in lakes. We firstly investigated the composition, spatial distribution, and potential environmental risks of MBP in the deep oligotrophic Fuxian Lake and shallow eutrophic Xingyun Lake using a pre-column cold trap enrichment-gas chromatography method. Results showed that the free gaseous phosphine (FGP) concentrations Fuxian Lake and Xingyun Lake were 5.39 ± 1.43 μg P/L and 8.81 ± 2.81 μg P/L, respectively, which accounted for approximately 31.87% to 73.75% of the soluble reactive phosphorus (SRP) in the overlying water, indicating that PH3 was an important component of the P cycle in both lakes. The total MBP (TMBP), porewater-soluble MBP (PMBP), and labile bound MBP (LMPB) in the sediments of Fuxian Lake and Xingyun Lake were 3.59 ± 0.89 ng/kg, 0.98 ± 0.24 ng/kg, and 0.68 ± 0.24 ng/kg; 122.84 ± 26.90 ng/kg, 0.83 ± 0.20 ng/kg, and 0.60 ± 0.18 ng/kg, respectively. TMBP concentrations in Xingyun Lake were found to be significantly higher than those in Fuxian Lake, with pronounced spatial heterogeneity in MBP distribution observed in both lakes. This heterogeneity was characterised by elevated concentrations in the northern regions compared to the southern and central areas, which served as primary inflow areas. The northern Fuxian Lake maintained persistent strongly anaerobic conditions which favored MBP generation. In contrast, the northern Xingyun Lake received substantial inputs of agricultural and domestic wastewater, providing important precusor substance for MBP production. These findings offered scientific insights into the biogeochemical P cycle in plateau lakes.
Matrix bound phosphine (MBP) in sediment is a widely existing yet often overlooked biologically available phosphorus pool in lakes. We firstly investigated the composition, spatial distribution, and potential environmental risks of MBP in the deep oligotrophic Fuxian Lake and shallow eutrophic Xingyun Lake using a pre-column cold trap enrichment-gas chromatography method. Results showed that the free gaseous phosphine (FGP) concentrations Fuxian Lake and Xingyun Lake were 5.39 ± 1.43 μg P/L and 8.81 ± 2.81 μg P/L, respectively, which accounted for approximately 31.87% to 73.75% of the soluble reactive phosphorus (SRP) in the overlying water, indicating that PH3 was an important component of the P cycle in both lakes. The total MBP (TMBP), porewater-soluble MBP (PMBP), and labile bound MBP (LMPB) in the sediments of Fuxian Lake and Xingyun Lake were 3.59 ± 0.89 ng/kg, 0.98 ± 0.24 ng/kg, and 0.68 ± 0.24 ng/kg; 122.84 ± 26.90 ng/kg, 0.83 ± 0.20 ng/kg, and 0.60 ± 0.18 ng/kg, respectively. TMBP concentrations in Xingyun Lake were found to be significantly higher than those in Fuxian Lake, with pronounced spatial heterogeneity in MBP distribution observed in both lakes. This heterogeneity was characterised by elevated concentrations in the northern regions compared to the southern and central areas, which served as primary inflow areas. The northern Fuxian Lake maintained persistent strongly anaerobic conditions which favored MBP generation. In contrast, the northern Xingyun Lake received substantial inputs of agricultural and domestic wastewater, providing important precusor substance for MBP production. These findings offered scientific insights into the biogeochemical P cycle in plateau lakes.
2026,(2):000-000, DOI: 10.18307/2026.0231
Available online: September 22, 2025
Abstract:
Under the context of global warming, the Qinghai-Tibet Plateau has given rise to diverse glacial lakes, with glacier retreat influencing microbial community composition and distribution in these lakes by altering aquatic environmental conditions. Investigating the heterogeneity of unique algal communities and their assembly mechanisms across different glacial lake types is crucial for understanding eukaryotic phytoplankton distribution patterns and their responses to environmental changes in the Tibetan Plateau"s glacial lakes. This study examined 10 glacial lakes in the Kuoqionggangri Glacier region of the southern Qinghai-Tibet Plateau, classifying them into proglacial lakes, glacier-fed lakes, and non-glacier-fed lakes based on meltwater supply patterns. Using 18S rDNA amplicon sequencing, co-occurrence network analysis, and community assembly modeling, we assessed how different water supply modes affect eukaryotic phytoplankton communities. The results revealed that Chlorophyta dominated these glacial lakes, with proglacial lakes exhibiting the highest α-diversity, stable community structures, and assembly processes primarily driven by dispersal limitation. In contrast, glacier-fed lakes displayed fragmented community structures shaped mainly by heterogeneous selection, while non-glacier-fed lakes had the lowest α-diversity, relying on strong species interactions for stability, with stochastic processes dominating community assembly. Water conductivity and total dissolved solids significantly influenced α-diversity, whereas nutrients had limited effects. These findings highlight the heterogeneity among glacial lake types in species composition, α- and β-diversity, community stability, assembly mechanisms, and environmental relationships, providing key insights into microbial community dynamics and ecological responses to environmental changes in high-altitude glacial lake ecosystems.
Under the context of global warming, the Qinghai-Tibet Plateau has given rise to diverse glacial lakes, with glacier retreat influencing microbial community composition and distribution in these lakes by altering aquatic environmental conditions. Investigating the heterogeneity of unique algal communities and their assembly mechanisms across different glacial lake types is crucial for understanding eukaryotic phytoplankton distribution patterns and their responses to environmental changes in the Tibetan Plateau"s glacial lakes. This study examined 10 glacial lakes in the Kuoqionggangri Glacier region of the southern Qinghai-Tibet Plateau, classifying them into proglacial lakes, glacier-fed lakes, and non-glacier-fed lakes based on meltwater supply patterns. Using 18S rDNA amplicon sequencing, co-occurrence network analysis, and community assembly modeling, we assessed how different water supply modes affect eukaryotic phytoplankton communities. The results revealed that Chlorophyta dominated these glacial lakes, with proglacial lakes exhibiting the highest α-diversity, stable community structures, and assembly processes primarily driven by dispersal limitation. In contrast, glacier-fed lakes displayed fragmented community structures shaped mainly by heterogeneous selection, while non-glacier-fed lakes had the lowest α-diversity, relying on strong species interactions for stability, with stochastic processes dominating community assembly. Water conductivity and total dissolved solids significantly influenced α-diversity, whereas nutrients had limited effects. These findings highlight the heterogeneity among glacial lake types in species composition, α- and β-diversity, community stability, assembly mechanisms, and environmental relationships, providing key insights into microbial community dynamics and ecological responses to environmental changes in high-altitude glacial lake ecosystems.
2026,(2):000-000, DOI: 10.18307/2026.0253
Available online: September 22, 2025
Abstract:
Abstract: Reservoir tributaries are important areas for the production and release of greenhouse gas (GHG) due to their special hydrological conditions and biogeochemical processes. In this study, the spatial and temporal distribution characteristics and formation mechanisms of CH?, CO? and N?O were systematically investigated by high-resolution vertical sampling in Yongping River, a tributary of Xiaowan Reservoir of Lancang River. The results showed that significant thermodynamic stratification existed in the study area, and the stability of stratification was significantly stronger in the dry water period (IC = 3.87) than in the abundant water period (IC = 5.72). The stratification structure of the water column affected the characteristics of the vertical distribution of GHG, and the stable stratification led to a CH? concentration of 2.085 μmol/L in the bottom layer, which was much larger than that in the surface layer; CO? appeared to have a maximum value in the thermocline (121.37 μmol/L); and N?O concentration was elevated at the sediment-water interface. Apparent oxygen consumption was significantly and positively correlated with ΔCO? (R2 = 0.46 during the dry period and R2 = 0.15 during the abundant period), suggesting that organic matter degradation is an important source of CO? production. Spatially, the mean value of CO? equivalent in the river-phase section was 641.31 mg CO?eq/m2/d, and its emission gradually decreased as the point was close to the reservoir area; the transition section was the hotspot of GHG emission, and its mean value of CO? equivalent amounted to 764.79 mg CO?eq/m2/d; and the lake-phase section had the smallest CO? equivalent value of 434.49 CO?eq/m2/d. Temporally, the total emission of GHG was 808.79 mg CO? equivalent in the dry season. The total GHG emission of 808.64 mg CO?eq/m2/d was higher than that of 440.64 mg CO?eq/m2/d during the abundant water period, and this difference was more prominent in the lake-phase section and the transition section, while it was not obvious in the river-phase section. Overall, the construction of the reservoir made the transitional section of the tributary become a hotspot of GHG emission, and caused obvious seasonal differences between the transitional section and the lake-phase section. In addition, the tributary GHG emission (624.64 mg CO2eq/m2/d) was larger than that of the main reservoir (337.06 mg CO2eq/m2/d). Therefore, the contribution of tributaries to reservoir GHG emissions cannot be ignored. This study preliminarily elucidated the vertical characteristics and formation mechanism of the GHG distribution in the reservoir tributaries, and suggested that the transition section should be the key monitoring area, and the research results provide important references for the assessment of GHG emissions from the reservoir tributaries and the formulation of emission reduction strategies.
Abstract: Reservoir tributaries are important areas for the production and release of greenhouse gas (GHG) due to their special hydrological conditions and biogeochemical processes. In this study, the spatial and temporal distribution characteristics and formation mechanisms of CH?, CO? and N?O were systematically investigated by high-resolution vertical sampling in Yongping River, a tributary of Xiaowan Reservoir of Lancang River. The results showed that significant thermodynamic stratification existed in the study area, and the stability of stratification was significantly stronger in the dry water period (IC = 3.87) than in the abundant water period (IC = 5.72). The stratification structure of the water column affected the characteristics of the vertical distribution of GHG, and the stable stratification led to a CH? concentration of 2.085 μmol/L in the bottom layer, which was much larger than that in the surface layer; CO? appeared to have a maximum value in the thermocline (121.37 μmol/L); and N?O concentration was elevated at the sediment-water interface. Apparent oxygen consumption was significantly and positively correlated with ΔCO? (R2 = 0.46 during the dry period and R2 = 0.15 during the abundant period), suggesting that organic matter degradation is an important source of CO? production. Spatially, the mean value of CO? equivalent in the river-phase section was 641.31 mg CO?eq/m2/d, and its emission gradually decreased as the point was close to the reservoir area; the transition section was the hotspot of GHG emission, and its mean value of CO? equivalent amounted to 764.79 mg CO?eq/m2/d; and the lake-phase section had the smallest CO? equivalent value of 434.49 CO?eq/m2/d. Temporally, the total emission of GHG was 808.79 mg CO? equivalent in the dry season. The total GHG emission of 808.64 mg CO?eq/m2/d was higher than that of 440.64 mg CO?eq/m2/d during the abundant water period, and this difference was more prominent in the lake-phase section and the transition section, while it was not obvious in the river-phase section. Overall, the construction of the reservoir made the transitional section of the tributary become a hotspot of GHG emission, and caused obvious seasonal differences between the transitional section and the lake-phase section. In addition, the tributary GHG emission (624.64 mg CO2eq/m2/d) was larger than that of the main reservoir (337.06 mg CO2eq/m2/d). Therefore, the contribution of tributaries to reservoir GHG emissions cannot be ignored. This study preliminarily elucidated the vertical characteristics and formation mechanism of the GHG distribution in the reservoir tributaries, and suggested that the transition section should be the key monitoring area, and the research results provide important references for the assessment of GHG emissions from the reservoir tributaries and the formulation of emission reduction strategies.
Nie Minchuan, Yao Jing, Gong Leiqiang, Cai Yongjiu, Xiong Lili, Liang Hanwei, Wang Xiaolong, Tan Zhiqiang
2026,(2):000-000, DOI: 10.18307/2026.0241
Available online: September 16, 2025
Abstract:
Under the combined influence of multiple factors such as inflow from the Yangtze River and the Five Rivers Basin, extreme flood-drought events in Poyang Lake have occurred frequently in recent years, with rapid shifts between floods and droughts observed from 2020 to 2024, leading to increased uncertainty in hydrological regimes. This study integrated LSTM neural networks and the MIKE21 hydrodynamic model to construct three scenarios: measured boundary conditions, scenarios excluding Three Gorges Reservoir (TGR) regulation, and scenarios with average annual basin inflow. A scenario comparison method was systematically applied to analyze the impacts of TGR regulation and basin inflow on extreme flood-drought events in Poyang Lake since 2020. Key findings include: (1) TGR regulation positively mitigated flood peaks, reducing the maximum water level drop at Xingzi Station during extreme floods by 1.35 m. Conversely, basin inflow negatively affected low-water stability, exacerbating the maximum water level drop at Xingzi Station during extreme droughts by 3.26 m. (2) Under combined effects, TGR regulation dominated extreme flood water level variations (reduction of 0.09–0.38 m, contributing 58%–81%), while basin inflow was the primary driver of droughts, significantly lowering dry-season water levels (reduction of 0.13–1.12 m, contributing 35%–100%). (3) During extreme floods, TGR regulation impacted the entire lake area, reducing water levels by up to 1.32–1.38 m with diminishing effects from north to south. During extreme droughts, basin inflow predominantly affected the main channel and southern Fuhe River inflow zone, lowering water levels by 0–3.96 m and reducing water surface area by 516.03 km2. This research provides scientific support for water resource management, extreme disaster early warning, and ecological protection in the middle and lower Yangtze River basin.
Under the combined influence of multiple factors such as inflow from the Yangtze River and the Five Rivers Basin, extreme flood-drought events in Poyang Lake have occurred frequently in recent years, with rapid shifts between floods and droughts observed from 2020 to 2024, leading to increased uncertainty in hydrological regimes. This study integrated LSTM neural networks and the MIKE21 hydrodynamic model to construct three scenarios: measured boundary conditions, scenarios excluding Three Gorges Reservoir (TGR) regulation, and scenarios with average annual basin inflow. A scenario comparison method was systematically applied to analyze the impacts of TGR regulation and basin inflow on extreme flood-drought events in Poyang Lake since 2020. Key findings include: (1) TGR regulation positively mitigated flood peaks, reducing the maximum water level drop at Xingzi Station during extreme floods by 1.35 m. Conversely, basin inflow negatively affected low-water stability, exacerbating the maximum water level drop at Xingzi Station during extreme droughts by 3.26 m. (2) Under combined effects, TGR regulation dominated extreme flood water level variations (reduction of 0.09–0.38 m, contributing 58%–81%), while basin inflow was the primary driver of droughts, significantly lowering dry-season water levels (reduction of 0.13–1.12 m, contributing 35%–100%). (3) During extreme floods, TGR regulation impacted the entire lake area, reducing water levels by up to 1.32–1.38 m with diminishing effects from north to south. During extreme droughts, basin inflow predominantly affected the main channel and southern Fuhe River inflow zone, lowering water levels by 0–3.96 m and reducing water surface area by 516.03 km2. This research provides scientific support for water resource management, extreme disaster early warning, and ecological protection in the middle and lower Yangtze River basin.
2026,(2):000-000, DOI: 10.18307/2026.0243
Available online: September 16, 2025
Abstract:
The Tibetan Plateau, a globally sensitive region to climate change, exhibits significant implications of its high-altitude lake surface water temperature (LSWT) evolution for regional ecological security. When exploring the factors influencing lake water temperature changes, various influencing factors are involved, such as meteorological conditions and topography. However, conventional methodologies demonstrate limited capacity in quantitatively resolving nonlinear interactive effects among multiple drivers. This study investigated 106 large-medium lakes across the Tibetan Plateau, developing a deep learning model based on Long Short-Term Memory (LSTM) networks integrated with SHapley Additive explanation (SHAP) interpretability analysis. We quantitatively differentiated the individual and interactive contributions of seven drivers (air temperature, precipitation, downward longwave radiation, downward shortwave radiation, air pressure, specific humidity, and wind speed) to LSWT variations at both regional and individual lake scales, systematically elucidating driving mechanisms and synergistic patterns. Key findings reveal: (1) Longwave and shortwave radiation emerged as dominant drivers, collectively contributing more than 80.0% of global SHAP values across scales, exhibiting significant positive correlations with LSWT. Air temperature and specific humidity demonstrated secondary influences, while precipitation and wind speed showed minimal impacts. (2) Ubiquitous interactive effects identified four predominant synergistic modes: linear pattern (e.g., downward longwave radiation-air temperature, 67.92% lakes), inverted U-shape pattern (e.g., specific humidity-air temperature, 51.89% lakes), effect cross-driven pattern (e.g., wind speed-specific humidity, 70.75% lakes), and threshold-constrained pattern (e.g., precipitation-air pressure, 100% lakes). (3) SHAP methodology effectively quantified nonlinear synergistic characteristics, revealing plateau lakes" heightened sensitivity to radiative factors attributable to high solar radiation permeability under thin atmospheric conditions. This study innovatively integrates deep learning with interpretability analysis, establishing a quantitative framework for disentangling complex driving mechanisms of high-altitude LSWT. The findings provide critical insights for predicting thermal responses under climate change and formulating differentiated regulatory strategies, bearing substantial practical scientific significance.
The Tibetan Plateau, a globally sensitive region to climate change, exhibits significant implications of its high-altitude lake surface water temperature (LSWT) evolution for regional ecological security. When exploring the factors influencing lake water temperature changes, various influencing factors are involved, such as meteorological conditions and topography. However, conventional methodologies demonstrate limited capacity in quantitatively resolving nonlinear interactive effects among multiple drivers. This study investigated 106 large-medium lakes across the Tibetan Plateau, developing a deep learning model based on Long Short-Term Memory (LSTM) networks integrated with SHapley Additive explanation (SHAP) interpretability analysis. We quantitatively differentiated the individual and interactive contributions of seven drivers (air temperature, precipitation, downward longwave radiation, downward shortwave radiation, air pressure, specific humidity, and wind speed) to LSWT variations at both regional and individual lake scales, systematically elucidating driving mechanisms and synergistic patterns. Key findings reveal: (1) Longwave and shortwave radiation emerged as dominant drivers, collectively contributing more than 80.0% of global SHAP values across scales, exhibiting significant positive correlations with LSWT. Air temperature and specific humidity demonstrated secondary influences, while precipitation and wind speed showed minimal impacts. (2) Ubiquitous interactive effects identified four predominant synergistic modes: linear pattern (e.g., downward longwave radiation-air temperature, 67.92% lakes), inverted U-shape pattern (e.g., specific humidity-air temperature, 51.89% lakes), effect cross-driven pattern (e.g., wind speed-specific humidity, 70.75% lakes), and threshold-constrained pattern (e.g., precipitation-air pressure, 100% lakes). (3) SHAP methodology effectively quantified nonlinear synergistic characteristics, revealing plateau lakes" heightened sensitivity to radiative factors attributable to high solar radiation permeability under thin atmospheric conditions. This study innovatively integrates deep learning with interpretability analysis, establishing a quantitative framework for disentangling complex driving mechanisms of high-altitude LSWT. The findings provide critical insights for predicting thermal responses under climate change and formulating differentiated regulatory strategies, bearing substantial practical scientific significance.
2026,(2):000-000, DOI: 10.18307/2026.0242
Available online: September 15, 2025
Abstract:
Baihetan Hydropower Station is the second stage of the lower reaches of the Jinsha River, with frequent landslides and mudslides in the reservoir area, and a large amount of sand production. After the reservoir impoundment, a large amount of sediment will be deposited in the reservoir area, damaging the capacity of the reservoir, and affecting the play of the comprehensive benefits of the reservoir. Based on the measured cross-section data of Baihetan Reservoir, the spatial and temporal evolution of sedimentation before and after impoundment was analyzed. The results show that: before impoundment (2013-2021), the sediment deposition process of the main river channel is “first silt and then flush”, and the other four tributaries basically maintain the balance of siltation and flushing except for the cumulative siltation of the Heishui River; after impoundment (2021-2023), a total of 82,796,000m3 of silt was deposited in the reservoir area, the proportion of siltation in dry and branch streams is 75.2% and 24.8% respectively, and the tributaries are most silted up by Heishui River and Xiaojiang River. From the inter-annual distribution, affected by high dams and reservoirs on sediment density and sedimentation, the siltation of dry tributaries is mainly concentrated in the first year after the formation of reservoirs, accounting for 71.8% of the total amount of siltation, and then the amount of siltation decreases year by year, and the phenomenon of “pseudo-scouring” appears in 2023. From the distribution within the year, the dry and tributary channels are silted during the flood season of each year, and scouring is dominant during the non-flood season. From the longitudinal distribution of siltation, the change of the backwater area continues to be slightly flushed, sediment siltation is mainly in the mouth of the Xiaojiang River to the mouth of the Yili River; sediment particles along the process of the phenomenon of refinement is significant, the closer to the front of the dam, the smaller the median particle size. From the distribution of siltation of different characteristics of reservoir capacity, sediment is mainly silted below the dead water level, with 1.14% siltation of dead reservoir capacity; the range of dead water level~normal storage level in the reservoir area is mainly scouring, with the increase of regulating reservoir capacity by 0.14%. From the longitudinal profile form, under the influence of sand coming from the zone, the deep Hong uplift of the perennial backwater area below the mouth of the Pudu River is relatively uniform, and the average uplift height of different river sections ranges from 1.8 to 2.3m. From the siltation of the tributaries, the Pudu River is a band siltation, the estuary sections of the Yili River, Xiaojiang River and Daqiao River show delta siltation, and the Heishui River is greatly affected by the backwater of dry-flow sediments and there is a risk of formation of barrage sand.
Baihetan Hydropower Station is the second stage of the lower reaches of the Jinsha River, with frequent landslides and mudslides in the reservoir area, and a large amount of sand production. After the reservoir impoundment, a large amount of sediment will be deposited in the reservoir area, damaging the capacity of the reservoir, and affecting the play of the comprehensive benefits of the reservoir. Based on the measured cross-section data of Baihetan Reservoir, the spatial and temporal evolution of sedimentation before and after impoundment was analyzed. The results show that: before impoundment (2013-2021), the sediment deposition process of the main river channel is “first silt and then flush”, and the other four tributaries basically maintain the balance of siltation and flushing except for the cumulative siltation of the Heishui River; after impoundment (2021-2023), a total of 82,796,000m3 of silt was deposited in the reservoir area, the proportion of siltation in dry and branch streams is 75.2% and 24.8% respectively, and the tributaries are most silted up by Heishui River and Xiaojiang River. From the inter-annual distribution, affected by high dams and reservoirs on sediment density and sedimentation, the siltation of dry tributaries is mainly concentrated in the first year after the formation of reservoirs, accounting for 71.8% of the total amount of siltation, and then the amount of siltation decreases year by year, and the phenomenon of “pseudo-scouring” appears in 2023. From the distribution within the year, the dry and tributary channels are silted during the flood season of each year, and scouring is dominant during the non-flood season. From the longitudinal distribution of siltation, the change of the backwater area continues to be slightly flushed, sediment siltation is mainly in the mouth of the Xiaojiang River to the mouth of the Yili River; sediment particles along the process of the phenomenon of refinement is significant, the closer to the front of the dam, the smaller the median particle size. From the distribution of siltation of different characteristics of reservoir capacity, sediment is mainly silted below the dead water level, with 1.14% siltation of dead reservoir capacity; the range of dead water level~normal storage level in the reservoir area is mainly scouring, with the increase of regulating reservoir capacity by 0.14%. From the longitudinal profile form, under the influence of sand coming from the zone, the deep Hong uplift of the perennial backwater area below the mouth of the Pudu River is relatively uniform, and the average uplift height of different river sections ranges from 1.8 to 2.3m. From the siltation of the tributaries, the Pudu River is a band siltation, the estuary sections of the Yili River, Xiaojiang River and Daqiao River show delta siltation, and the Heishui River is greatly affected by the backwater of dry-flow sediments and there is a risk of formation of barrage sand.
2026,(2):000-000, DOI: 10.18307/2026.0251
Available online: September 12, 2025
Abstract:
In-lake dissolved carbon turnover is an important component of the global carbon cycle. However, previous studies largely focused on the hydro-chemical characteristics of dissolved inorganic carbon, with limited understanding of the internal linkages between dissolved inorganic carbon (DIC) and organic carbon (DOC). In this study, we aim to explore the mutual transformation among dissolved carbon components under seasonal changes in the Lugu Lake, Southwest China. We examined seasonal variations in DIC species (DIC, HCO3-, CO32-, and CO2) and DOC optical parameters (S275-295, SUVA254, SUVA280, URI, BIX, HIX and FI). In particular, we performed Fluorescence Region Integration (FRI) and Excitation-Emission Matrix Parallel Factor Analysis (EEM-PARAFAC), and measured partial pressure of CO2 (pCO2) and CO2 flux (F), to comprehensively assess dissolved carbon. Our results showed that carbonate dissolution caused significant seasonal differences in DIC species (P < 0.05). The significant seasonal variations in the spectral slope (S275-295) (P < 0.05) indicated the presence of allochthonous high-molecular-weight dissolved organic carbon inputs during the rainy season, and the high level of biological index (BIX) yet low level of humification index (HIX) suggested significant biological activity. Soluble microbial by-products were the primary DOC component, accounting for 44.53% to 71.97% on average, with humic-like and tryptophan-like DOC being dominant in the lake. During the rainy season, Lake Lugu acts as a pronounced CO2 source driven by intense microbial mineralization of DOC（pCO2 > 470 μatm，F > 0）. Overall, this study elucidates the variations in DIC and DOC in Lake Lugu across rainy and dry seasons, revealing the transformation patterns driven by seasonal microbial metabolism within the dissolved carbon pool. Specifically, respiratory processes dominate during the rainy season, mineralizing DIC into CO2, while photosynthetic activity prevails during the dry season. These findings offer novel insights into natural aquatic carbon fixation and sequestration in lakes.
In-lake dissolved carbon turnover is an important component of the global carbon cycle. However, previous studies largely focused on the hydro-chemical characteristics of dissolved inorganic carbon, with limited understanding of the internal linkages between dissolved inorganic carbon (DIC) and organic carbon (DOC). In this study, we aim to explore the mutual transformation among dissolved carbon components under seasonal changes in the Lugu Lake, Southwest China. We examined seasonal variations in DIC species (DIC, HCO3-, CO32-, and CO2) and DOC optical parameters (S275-295, SUVA254, SUVA280, URI, BIX, HIX and FI). In particular, we performed Fluorescence Region Integration (FRI) and Excitation-Emission Matrix Parallel Factor Analysis (EEM-PARAFAC), and measured partial pressure of CO2 (pCO2) and CO2 flux (F), to comprehensively assess dissolved carbon. Our results showed that carbonate dissolution caused significant seasonal differences in DIC species (P < 0.05). The significant seasonal variations in the spectral slope (S275-295) (P < 0.05) indicated the presence of allochthonous high-molecular-weight dissolved organic carbon inputs during the rainy season, and the high level of biological index (BIX) yet low level of humification index (HIX) suggested significant biological activity. Soluble microbial by-products were the primary DOC component, accounting for 44.53% to 71.97% on average, with humic-like and tryptophan-like DOC being dominant in the lake. During the rainy season, Lake Lugu acts as a pronounced CO2 source driven by intense microbial mineralization of DOC（pCO2 > 470 μatm，F > 0）. Overall, this study elucidates the variations in DIC and DOC in Lake Lugu across rainy and dry seasons, revealing the transformation patterns driven by seasonal microbial metabolism within the dissolved carbon pool. Specifically, respiratory processes dominate during the rainy season, mineralizing DIC into CO2, while photosynthetic activity prevails during the dry season. These findings offer novel insights into natural aquatic carbon fixation and sequestration in lakes.
2026,(2):000-000, DOI: 10.18307/2026.0221
Available online: September 09, 2025
Abstract:
Based on self-developed two-dimensional micro-scale diffusive gradients in thin films (2D-MDGT) and planar optode (PO) techniques, this study, for the first time, conducted in-situ investigations of the spatiotemporal variations of labile phosphorus (Labile-P), soluble reactive phosphorus (SRP), ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-) at the sediment-water interface (SWI) of Ulansuhai Lake, a typical cold and arid zone lake, during both freezing and unfreezing periods. Simultaneously, the micro-environmental characteristics of SWI, including pH and dissolved oxygen (DO), were monitored. Furthermore, the exchange fluxes at the SWI were analyzed in situ. The results revealed significant spatial and temporal heterogeneity in the concentrations of the five nitrogen (N) and phosphorus (P) species across all sediment profiles, with statistically significant differences (P < 0.05). During the freezing period, the average concentrations of Labile-P, SRP, NH4+, NO2- and NO3- were 0.006 ± 0.005 mg/L, 0.096 ± 0.07 mg/L, 2.71 ± 0.502 mg/L, 0.149 ± 0.061 mg/L, and 0.482 ± 0.475 mg/L, respectively, which were significantly lower than those during the unfreezing period (0.06 ± 0.036 mg/L, 0.153 ± 0.162 mg/L, 24.276 ± 1.714 mg/L, 0.36 ± 0.042 mg/L, and 1.359 ± 1.09 mg/L, respectively). Vertically, the concentrations of Labile-P, SRP, and NH4+ increased with depth, while NO3- concentrations decreased with depth. In contrast, NO2- concentrations showed no significant variation with depth. Horizontally, the northern region of the lake exhibited higher concentrations of N and P species in the sediment profiles, which was attributed to higher P accumulation and intense oxygen-consuming reductive processes. The in-situ measured exchange fluxes of Labile-P, SRP, NH4+, NO2- and NO3- ranged from -0.322 to 25.787 μg.m?2.d?1, -3.909 to 35.659 μg.m?2.d?1, -18.043 to 6.940 mg.m?2.d?1, -1.532 to 8.026 mg.m?2.d?1, and -0.222 to 0.145 mg.m?2.d?1, respectively. Notably, the unfreezing period exhibited a strong release of N and P, which significantly increases the risk of water quality deterioration in the lake.
Based on self-developed two-dimensional micro-scale diffusive gradients in thin films (2D-MDGT) and planar optode (PO) techniques, this study, for the first time, conducted in-situ investigations of the spatiotemporal variations of labile phosphorus (Labile-P), soluble reactive phosphorus (SRP), ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-) at the sediment-water interface (SWI) of Ulansuhai Lake, a typical cold and arid zone lake, during both freezing and unfreezing periods. Simultaneously, the micro-environmental characteristics of SWI, including pH and dissolved oxygen (DO), were monitored. Furthermore, the exchange fluxes at the SWI were analyzed in situ. The results revealed significant spatial and temporal heterogeneity in the concentrations of the five nitrogen (N) and phosphorus (P) species across all sediment profiles, with statistically significant differences (P < 0.05). During the freezing period, the average concentrations of Labile-P, SRP, NH4+, NO2- and NO3- were 0.006 ± 0.005 mg/L, 0.096 ± 0.07 mg/L, 2.71 ± 0.502 mg/L, 0.149 ± 0.061 mg/L, and 0.482 ± 0.475 mg/L, respectively, which were significantly lower than those during the unfreezing period (0.06 ± 0.036 mg/L, 0.153 ± 0.162 mg/L, 24.276 ± 1.714 mg/L, 0.36 ± 0.042 mg/L, and 1.359 ± 1.09 mg/L, respectively). Vertically, the concentrations of Labile-P, SRP, and NH4+ increased with depth, while NO3- concentrations decreased with depth. In contrast, NO2- concentrations showed no significant variation with depth. Horizontally, the northern region of the lake exhibited higher concentrations of N and P species in the sediment profiles, which was attributed to higher P accumulation and intense oxygen-consuming reductive processes. The in-situ measured exchange fluxes of Labile-P, SRP, NH4+, NO2- and NO3- ranged from -0.322 to 25.787 μg.m?2.d?1, -3.909 to 35.659 μg.m?2.d?1, -18.043 to 6.940 mg.m?2.d?1, -1.532 to 8.026 mg.m?2.d?1, and -0.222 to 0.145 mg.m?2.d?1, respectively. Notably, the unfreezing period exhibited a strong release of N and P, which significantly increases the risk of water quality deterioration in the lake.
2026,(2):000-000, DOI: 10.18307/2026.0211
Available online: September 09, 2025
Abstract:
Through years of integrated remediation efforts, the prevention and control of cyanobacterial blooms in Lake Dianchi have achieved remarkable interim progress. Since 2018, both the annual frequency of cyanobacterial blooms and the spatial extent of blooms have exhibited a sustained declining trend. However, a notable resurgence of cyanobacterial blooms was observed in 2023, drawing significant scientific and public attention. This study systematically analyzed the variation characteristics and outbreak mechanisms of cyanobacterial blooms in Lake Dianchi based on MODIS satellite imagery data (2018-2023) and integrated water quality and meteorological monitoring data. The monitoring data indicated that over the past six years, the annual frequency of cyanobacterial blooms in Lake Dianchi exhibited a "V"-shaped trend, with the value in 2023 (87.0%) being significantly higher than the six-year average (69.3%). The average cyanobacterial bloom area from 2022 to 2023 was markedly lower than that from 2018 to 2021. Specifically, the average cyanobacterial bloom area in 2023 (15.86 km2) was 65.3% lower than the six-year mean, though it showed an 11.4% increase compared to 2022. Spearman correlation analysis revealed that the frequency of cyanobacterial blooms and the average bloom area were significantly positively correlated with air temperature and precipitation but significantly negatively correlated with wind speed. Additionally, cyanobacterial density showed a significant positive correlation with total phosphorus. Multivariate linear regression analysis demonstrated that air temperature and wind speed were the key meteorological factors regulating cyanobacterial blooms in Lake Dianchi, whereas the explanatory power of total phosphorus concentration for variations in algal density was limited. Against the background of cyanobacterial density persistently exceeding the mild bloom threshold (1.0×10? cells/L) from 2018 to 2023, the rebound of cyanobacterial conditions in Lake Dianchi in 2023 was primarily driven by the synergistic regulation of meteorological factors. More specifically, during the non-bloom period (January-May and December), the increased proportion of 13-20°C temperatures accelerated cyanobacterial resurgence. In the bloom period (June-November), the higher frequency of low wind speeds (<2 m/s) facilitated cyanobacterial surfacing and aggregation, while the decreased proportion of temperatures below 13°C favored cyanobacterial proliferation. These combined factors likely contributed to the elevated incidence of algal blooms observed in 2023. Moreover, the significantly increased proportion of high temperatures (20–25°C) during the bloom period likely enhanced cyanobacterial buoyancy, serving as a key driver for the expansion of bloom coverage that year. The findings not only provide theoretical support for the daily prevention, prediction, and early warning of cyanobacterial blooms in Lake Dianchi, but also offer scientific references for managing cyanobacterial blooms in other plateau lakes in Yunnan Province.
Through years of integrated remediation efforts, the prevention and control of cyanobacterial blooms in Lake Dianchi have achieved remarkable interim progress. Since 2018, both the annual frequency of cyanobacterial blooms and the spatial extent of blooms have exhibited a sustained declining trend. However, a notable resurgence of cyanobacterial blooms was observed in 2023, drawing significant scientific and public attention. This study systematically analyzed the variation characteristics and outbreak mechanisms of cyanobacterial blooms in Lake Dianchi based on MODIS satellite imagery data (2018-2023) and integrated water quality and meteorological monitoring data. The monitoring data indicated that over the past six years, the annual frequency of cyanobacterial blooms in Lake Dianchi exhibited a "V"-shaped trend, with the value in 2023 (87.0%) being significantly higher than the six-year average (69.3%). The average cyanobacterial bloom area from 2022 to 2023 was markedly lower than that from 2018 to 2021. Specifically, the average cyanobacterial bloom area in 2023 (15.86 km2) was 65.3% lower than the six-year mean, though it showed an 11.4% increase compared to 2022. Spearman correlation analysis revealed that the frequency of cyanobacterial blooms and the average bloom area were significantly positively correlated with air temperature and precipitation but significantly negatively correlated with wind speed. Additionally, cyanobacterial density showed a significant positive correlation with total phosphorus. Multivariate linear regression analysis demonstrated that air temperature and wind speed were the key meteorological factors regulating cyanobacterial blooms in Lake Dianchi, whereas the explanatory power of total phosphorus concentration for variations in algal density was limited. Against the background of cyanobacterial density persistently exceeding the mild bloom threshold (1.0×10? cells/L) from 2018 to 2023, the rebound of cyanobacterial conditions in Lake Dianchi in 2023 was primarily driven by the synergistic regulation of meteorological factors. More specifically, during the non-bloom period (January-May and December), the increased proportion of 13-20°C temperatures accelerated cyanobacterial resurgence. In the bloom period (June-November), the higher frequency of low wind speeds (<2 m/s) facilitated cyanobacterial surfacing and aggregation, while the decreased proportion of temperatures below 13°C favored cyanobacterial proliferation. These combined factors likely contributed to the elevated incidence of algal blooms observed in 2023. Moreover, the significantly increased proportion of high temperatures (20–25°C) during the bloom period likely enhanced cyanobacterial buoyancy, serving as a key driver for the expansion of bloom coverage that year. The findings not only provide theoretical support for the daily prevention, prediction, and early warning of cyanobacterial blooms in Lake Dianchi, but also offer scientific references for managing cyanobacterial blooms in other plateau lakes in Yunnan Province.
2026,(2):000-000, DOI: 10.18307/2026.0225
Available online: September 08, 2025
Abstract:
The bioavailability of dissolved organic carbon (DOC), i.e., %BDOC, has received increasing attention in recent years. The %BDOC level directly affects the biogeochemical behavior of organic matter as well as the toxicity and bioavailability of heavy metals and pollutants. Lake Taihu Basin, situated in the economically advanced Yangtze River Delta region of China, has faced severe pollution due to large-scale industrial and domestic wastewater discharge over recent decades, posing a significant threat to drinking water safety for residents. Investigating the %BDOC in Lake Taihu is crucial for understanding lake carbon cycling and ensuring safe water supplies in the region. Long-term bio-incubation experiments were conducted to explore the spatial and temporal variations and the main factors influencing %BDOC in Lake Taihu from August 2018 to May 2021. The study revealed that %BDOC in Lake Taihu was higher in February and May compared to August and November, following a decreasing trend from northwest to southeast, with the highest levels observed in Zhushan Bay. After 28 days of bioincubation, tryptophan-like C2 and red-shifted tyrosine-like C3 levels showed significant reductions compared to pre-incubation levels (t-test, p<0.001). The fluorescence intensity of protein-like components was found to directly influence %BDOC in Lake Taihu, and these components exhibited high bioavailability. Pearson correlation analysis, random forest modeling, and partial least squares (PLS) regression were employed to comprehensive analyze %BDOC and its associated physicochemical parameters. Results indicated that %BDOC was significantly and negatively correlated with SUVA254 (aromaticity level) and positively correlated with DOC, COD, TN, and TP. Dissolved oxygen was identified as a key indicator of %BDOC variations in Lake Taihu. Enhanced research and monitoring of lake %BDOC are pivotal for elucidating organic matter dynamics, assessing carbon emission potential, and protecting water supplies.
The bioavailability of dissolved organic carbon (DOC), i.e., %BDOC, has received increasing attention in recent years. The %BDOC level directly affects the biogeochemical behavior of organic matter as well as the toxicity and bioavailability of heavy metals and pollutants. Lake Taihu Basin, situated in the economically advanced Yangtze River Delta region of China, has faced severe pollution due to large-scale industrial and domestic wastewater discharge over recent decades, posing a significant threat to drinking water safety for residents. Investigating the %BDOC in Lake Taihu is crucial for understanding lake carbon cycling and ensuring safe water supplies in the region. Long-term bio-incubation experiments were conducted to explore the spatial and temporal variations and the main factors influencing %BDOC in Lake Taihu from August 2018 to May 2021. The study revealed that %BDOC in Lake Taihu was higher in February and May compared to August and November, following a decreasing trend from northwest to southeast, with the highest levels observed in Zhushan Bay. After 28 days of bioincubation, tryptophan-like C2 and red-shifted tyrosine-like C3 levels showed significant reductions compared to pre-incubation levels (t-test, p<0.001). The fluorescence intensity of protein-like components was found to directly influence %BDOC in Lake Taihu, and these components exhibited high bioavailability. Pearson correlation analysis, random forest modeling, and partial least squares (PLS) regression were employed to comprehensive analyze %BDOC and its associated physicochemical parameters. Results indicated that %BDOC was significantly and negatively correlated with SUVA254 (aromaticity level) and positively correlated with DOC, COD, TN, and TP. Dissolved oxygen was identified as a key indicator of %BDOC variations in Lake Taihu. Enhanced research and monitoring of lake %BDOC are pivotal for elucidating organic matter dynamics, assessing carbon emission potential, and protecting water supplies.
2026,(2):000-000, DOI: 10.18307/2026.0213
Available online: September 08, 2025
Abstract:
Algae serve as crucial primary producers in lake ecosystems, with their biomass and community structure acting as indicators of water pollution and ecological status. Diatoms, being a major component of algae, exhibit species composition characteristics that are sensitive markers for assessing lake environmental quality. However, systematic analyses remain scarce regarding whether distinct patterns and response mechanisms of algal biomass and diatom communities exist across lakes with varying pollution levels. This study conducted seasonal surveys and comparative analyses on three plateau lakes in Yunnan Province with different levels of arsenic (As) pollution gradient, including As-polluted Datun and Yangzong, as well as non-As-polluted Yilong, aiming to identify the seasonal variations, driving factors and key processes in algal changes under varying As pollution levels. Analysis of 55 surface water samples revealed the highest chlorophyll-a (Chl.a) concentrations in the eutrophic Dian Lake. Diatom composition differed significantly between lakes and exhibited marked seasonal fluctuations. Correlation analysis showed that the seasonal variations of arsenic and Chl.a concentration presented a significant positive correlation (p<0.05) across the three lakes, reflecting that algae had strong tolerance to long - term arsenic stress and there was a strong promotion effect with low As. Meanwhile, the main direction of diatom community changes was also significantly correlated with lake-water arsenic (p<0.05). Variance partitioning analysis of algal data and environmental factors indicated that key environmental gradients exerted a more pronounced influence on diatom community succession (represented by PC1, mean explained variance: 64.1%) than on Chl.a fluctuations (mean explained variance: 39.8%). Results further revealed that seasonal variations in aqueous As pollution were closely linked to water temperature and lake depth type: rising temperatures enhanced As chemical activity and increased aqueous As concentrations in shallow lakes, whereas in deep lakes, thermal stratification restricted both the diffusion of sediment-derived As and vertical migration of aqueous As. In conclusion, the interaction of As with water temperature, nutrient levels, and depth significantly influenced algal seasonal dynamics under varying pollution levels, leading to substantial differences in the response intensity of different algal indicators. Therefore, effective ecological remediation and assessment of As pollution in lakes necessitate integrated consideration of temperature and nutrient conditions, coupled with multi-indicator analysis incorporating both algal biomass and diom community structure.
Algae serve as crucial primary producers in lake ecosystems, with their biomass and community structure acting as indicators of water pollution and ecological status. Diatoms, being a major component of algae, exhibit species composition characteristics that are sensitive markers for assessing lake environmental quality. However, systematic analyses remain scarce regarding whether distinct patterns and response mechanisms of algal biomass and diatom communities exist across lakes with varying pollution levels. This study conducted seasonal surveys and comparative analyses on three plateau lakes in Yunnan Province with different levels of arsenic (As) pollution gradient, including As-polluted Datun and Yangzong, as well as non-As-polluted Yilong, aiming to identify the seasonal variations, driving factors and key processes in algal changes under varying As pollution levels. Analysis of 55 surface water samples revealed the highest chlorophyll-a (Chl.a) concentrations in the eutrophic Dian Lake. Diatom composition differed significantly between lakes and exhibited marked seasonal fluctuations. Correlation analysis showed that the seasonal variations of arsenic and Chl.a concentration presented a significant positive correlation (p<0.05) across the three lakes, reflecting that algae had strong tolerance to long - term arsenic stress and there was a strong promotion effect with low As. Meanwhile, the main direction of diatom community changes was also significantly correlated with lake-water arsenic (p<0.05). Variance partitioning analysis of algal data and environmental factors indicated that key environmental gradients exerted a more pronounced influence on diatom community succession (represented by PC1, mean explained variance: 64.1%) than on Chl.a fluctuations (mean explained variance: 39.8%). Results further revealed that seasonal variations in aqueous As pollution were closely linked to water temperature and lake depth type: rising temperatures enhanced As chemical activity and increased aqueous As concentrations in shallow lakes, whereas in deep lakes, thermal stratification restricted both the diffusion of sediment-derived As and vertical migration of aqueous As. In conclusion, the interaction of As with water temperature, nutrient levels, and depth significantly influenced algal seasonal dynamics under varying pollution levels, leading to substantial differences in the response intensity of different algal indicators. Therefore, effective ecological remediation and assessment of As pollution in lakes necessitate integrated consideration of temperature and nutrient conditions, coupled with multi-indicator analysis incorporating both algal biomass and diom community structure.
2026,(2):000-000, DOI: 10.18307/2026.0214
Available online: September 05, 2025
Abstract:
Chenghai Lake, a significant water body on the Yunnan-Guizhou Plateau, plays a pivotal role in the improvement of its watershed’s ecological environment. This is not only essential for Yunnan’s achievement of the three major ecological security tasks but also serves as the foundation for sustainable socio-economic development. In recent years, Chenghai"s water environment quality has faced serious challenges due to both human activities and natural factors. To investigate the spatiotemporal evolution characteristics of the trophic state and its key driving factors in Chenghai, a deep, closed lake, this study analyzes monitoring data from three regions of Chenghai Lake from 2010 to 2023. We employed M-K tests, Spearman"s rank correlation analysis, multiple linear regression models, and piecewise structural equation modeling to examine the spatiotemporal evolution of the lake’s trophic state, elucidate the direct driving effects of various factors on the trophic state, and explore their indirect pathways of influence. The aim of this study is to provide both theoretical insights and data support for the protection and management of Chenghai"s water environment. The results are as follows: (1) Between 2010 and 2023, the trophic state of Chenghai Lake showed a phased evolutionary pattern, predominantly remaining at a mesotrophic level. (2) Ecological water replenishment played a positive role in shifting the lake’s trophic state and its trends. Specifically, the comprehensive trophic state index (TLI(Σ)) in the southern and central regions showed a significant upward trend before water replenishment (2013–2018) (p < 0.01), and a significant downward trend after replenishment (2019–2023) (p < 0.05). No significant differences in TLI(Σ) were observed before and after replenishment across different regions, and the trophic state remained mesotrophic. (3) The trophic state of Chenghai Lake was significantly influenced by seasonality, with TLI(Σ) being higher during the colder spring and winter months compared to the warmer summer and autumn months. This may be attributed to the lake’s concentration effect and thermal stratification. (4) Physical and chemical factors are the main drivers of changes in TLI(Σ). Over all periods, nitrogen and phosphorus inputs, primarily from external sources, indirectly influenced TLI(Σ) by affecting other factors. Moreover, a series of ecological and environmental protection measures implemented in recent years have reduced the contribution of nitrogen and phosphorus inputs to TLI(Σ). It is important to note that despite significant ecological water replenishment, the trophic state of Chenghai Lake remains at a mesotrophic level. This indicates that the impact of terrestrial pollutant inputs and internal pollution on the lake’s trophic state should not be overlooked. Therefore, while maintaining and enhancing ecological water replenishment, a critical focus for future conservation efforts will be to reduce terrestrial pollutant inputs and remove pollutants from the lake’s water.
Chenghai Lake, a significant water body on the Yunnan-Guizhou Plateau, plays a pivotal role in the improvement of its watershed’s ecological environment. This is not only essential for Yunnan’s achievement of the three major ecological security tasks but also serves as the foundation for sustainable socio-economic development. In recent years, Chenghai"s water environment quality has faced serious challenges due to both human activities and natural factors. To investigate the spatiotemporal evolution characteristics of the trophic state and its key driving factors in Chenghai, a deep, closed lake, this study analyzes monitoring data from three regions of Chenghai Lake from 2010 to 2023. We employed M-K tests, Spearman"s rank correlation analysis, multiple linear regression models, and piecewise structural equation modeling to examine the spatiotemporal evolution of the lake’s trophic state, elucidate the direct driving effects of various factors on the trophic state, and explore their indirect pathways of influence. The aim of this study is to provide both theoretical insights and data support for the protection and management of Chenghai"s water environment. The results are as follows: (1) Between 2010 and 2023, the trophic state of Chenghai Lake showed a phased evolutionary pattern, predominantly remaining at a mesotrophic level. (2) Ecological water replenishment played a positive role in shifting the lake’s trophic state and its trends. Specifically, the comprehensive trophic state index (TLI(Σ)) in the southern and central regions showed a significant upward trend before water replenishment (2013–2018) (p < 0.01), and a significant downward trend after replenishment (2019–2023) (p < 0.05). No significant differences in TLI(Σ) were observed before and after replenishment across different regions, and the trophic state remained mesotrophic. (3) The trophic state of Chenghai Lake was significantly influenced by seasonality, with TLI(Σ) being higher during the colder spring and winter months compared to the warmer summer and autumn months. This may be attributed to the lake’s concentration effect and thermal stratification. (4) Physical and chemical factors are the main drivers of changes in TLI(Σ). Over all periods, nitrogen and phosphorus inputs, primarily from external sources, indirectly influenced TLI(Σ) by affecting other factors. Moreover, a series of ecological and environmental protection measures implemented in recent years have reduced the contribution of nitrogen and phosphorus inputs to TLI(Σ). It is important to note that despite significant ecological water replenishment, the trophic state of Chenghai Lake remains at a mesotrophic level. This indicates that the impact of terrestrial pollutant inputs and internal pollution on the lake’s trophic state should not be overlooked. Therefore, while maintaining and enhancing ecological water replenishment, a critical focus for future conservation efforts will be to reduce terrestrial pollutant inputs and remove pollutants from the lake’s water.
2026,(2):000-000, DOI: 10.18307/2026.0255
Available online: August 28, 2025
Abstract:
A comprehensive understanding of the absorption and emission characteristics of greenhouse gases is vital to estimating carbon budget in lakes. For the Poyang Lake, most efforts have been devoted to the study of wetland vegetation instead of that of open waters. Here we conducted high-frequency surface and profiling observations of CH? and CO? concentrations in a northern site of the Poyang Lake open waters during the last summer. The study revealed significant diurnal variations in water CO? concentrations. During daytime, surface CO? concentrations were lower (15.02 μmol/L), with distinct stratification observed in vertical profiles, while nighttime surface concentrations increased (22.30 μmol/L) and vertical gradients became less pronounced. In contrast, CH? concentrations exhibited strong fluctuations without clear diurnal patterns.?CO? concentrations showed significant negative correlations (p < 0.01) with dissolved oxygen (DO), water temperature and chlorophyll content, but positively correlated with relative humidity and nitrate-nitrogen concentrations. CH? concentrations were significantly positively correlated with net radiation irradiance and inorganic carbon (DIC) concentrations (p < 0.01),?and negatively correlated with net longwave radiation (p < 0.01). A single-time sampling is always not temporally representative of daily averages, and only daytime sampling might underestimate the CO? concentration by as high as 19.9%. For the Poyang Lake, the optimal sampling time is 14–16 时 for the CH? concentration, and is 10–12 时 for the CO? concentration. This study revealed the high-frequency diurnal variation characteristics of greenhouse gas concentrations in the Poyang Lake, providing support for quantifying the uncertainties associated with key variables in the carbon cycle and for accurately estimating the lake carbon budget.
A comprehensive understanding of the absorption and emission characteristics of greenhouse gases is vital to estimating carbon budget in lakes. For the Poyang Lake, most efforts have been devoted to the study of wetland vegetation instead of that of open waters. Here we conducted high-frequency surface and profiling observations of CH? and CO? concentrations in a northern site of the Poyang Lake open waters during the last summer. The study revealed significant diurnal variations in water CO? concentrations. During daytime, surface CO? concentrations were lower (15.02 μmol/L), with distinct stratification observed in vertical profiles, while nighttime surface concentrations increased (22.30 μmol/L) and vertical gradients became less pronounced. In contrast, CH? concentrations exhibited strong fluctuations without clear diurnal patterns.?CO? concentrations showed significant negative correlations (p < 0.01) with dissolved oxygen (DO), water temperature and chlorophyll content, but positively correlated with relative humidity and nitrate-nitrogen concentrations. CH? concentrations were significantly positively correlated with net radiation irradiance and inorganic carbon (DIC) concentrations (p < 0.01),?and negatively correlated with net longwave radiation (p < 0.01). A single-time sampling is always not temporally representative of daily averages, and only daytime sampling might underestimate the CO? concentration by as high as 19.9%. For the Poyang Lake, the optimal sampling time is 14–16 时 for the CH? concentration, and is 10–12 时 for the CO? concentration. This study revealed the high-frequency diurnal variation characteristics of greenhouse gas concentrations in the Poyang Lake, providing support for quantifying the uncertainties associated with key variables in the carbon cycle and for accurately estimating the lake carbon budget.
2026,(2):000-000, DOI: 10.18307/2026.0222
Available online: August 28, 2025
Abstract:
The Jiulong-Fenggang area on the south shore of Poyang Lake was selected as the study area to identify the pollution risks and sources of heavy metals in the soil within the Poyang Lake embankment region. A total of 3,799 topsoil samples and 26 soil profile samples were collected. The pollution status was assessed using three methods: the geoaccumulation index, the Nemerow index, and the potential ecological risk index. The positive definite matrix factor decomposition method (PMF) was employed to analyze the sources of heavy metals in the soil. The results indicated that the average concentrations of As, Cd, Cu, Cr, Hg, Ni, Pb, and Zn in the surface soil of the embankment area were 1.06 to 2.10 times higher than the background values of the soil in Jiangxi Province. The geoaccumulation index revealed a non-polluting to slightly polluting level. The comprehensive potential ecological risk index indicated primarily a low-risk level. The comprehensive Nemerow index suggested that the area was mainly non-polluted, with only the sampling sites in the tidal flats showing moderate to high levels of pollution, where Cd was the primary contributor. Due to the influence of the upstream water system, the concentrations of heavy metals, particularly Cd, in the vertical profile soil and surface soil in the tidal flats outside the embankment area were significantly elevated, exceeding the standards, while the heavy metal concentrations in the soil within the embankment area remained relatively stable. Joint analysis identified four sources of heavy metals in the soil: secondary enrichment during red soil formation (49.28%), upstream industrial and mining activities (20.19%), weathering of parent rocks in coal-bearing strata and agricultural production (11.91%), and coal combustion (18.62%). Notably, soil Cd primarily originated from upstream transport (79.92%), providing an effective basis for the precise prevention and control of heavy metal pollution in farmland within embankment areas and ensuring safe utilization.
The Jiulong-Fenggang area on the south shore of Poyang Lake was selected as the study area to identify the pollution risks and sources of heavy metals in the soil within the Poyang Lake embankment region. A total of 3,799 topsoil samples and 26 soil profile samples were collected. The pollution status was assessed using three methods: the geoaccumulation index, the Nemerow index, and the potential ecological risk index. The positive definite matrix factor decomposition method (PMF) was employed to analyze the sources of heavy metals in the soil. The results indicated that the average concentrations of As, Cd, Cu, Cr, Hg, Ni, Pb, and Zn in the surface soil of the embankment area were 1.06 to 2.10 times higher than the background values of the soil in Jiangxi Province. The geoaccumulation index revealed a non-polluting to slightly polluting level. The comprehensive potential ecological risk index indicated primarily a low-risk level. The comprehensive Nemerow index suggested that the area was mainly non-polluted, with only the sampling sites in the tidal flats showing moderate to high levels of pollution, where Cd was the primary contributor. Due to the influence of the upstream water system, the concentrations of heavy metals, particularly Cd, in the vertical profile soil and surface soil in the tidal flats outside the embankment area were significantly elevated, exceeding the standards, while the heavy metal concentrations in the soil within the embankment area remained relatively stable. Joint analysis identified four sources of heavy metals in the soil: secondary enrichment during red soil formation (49.28%), upstream industrial and mining activities (20.19%), weathering of parent rocks in coal-bearing strata and agricultural production (11.91%), and coal combustion (18.62%). Notably, soil Cd primarily originated from upstream transport (79.92%), providing an effective basis for the precise prevention and control of heavy metal pollution in farmland within embankment areas and ensuring safe utilization.
2026,(2):000-000, DOI: 10.18307/2026.0232
Available online: August 28, 2025
Abstract:
Seasonal hydroacoustic surveys, combined with net fishing data, were used to investigate the spatiotemporal distribution of fish resources in the lower Chishui River during 2023. The results showed that fish communities were primarily composed of Squalidus argentatus, Pelteobagrus vachelli, and Pseudobrama simoni, with notable seasonal variations in composition and abundance. Hydroacoustic results showed that the target strength (TS) of fish individuals exhibited a temporal pattern of February>October>June>August, while density peaked in June (June>August>October>February). Horizontal distribution showed higher densities near the Zhenlong Town, Xianshi Town, and Fuxing Town, with average densities of 16.12 ind/1000m3, 21.16 ind/1000m3, and 17.46 ind/1000m3, respectively. In terms of vertical distribution, the fish density is primarily concentrated in the lower layers. Geostatistical analysis estimated seasonal fish resources ranging from 2.94×105 (winter) to 1.72×106 (spring), exhibiting a patchy distribution related to water depth and channel morphology. Compared to historical data, our results indicated an initial recovery of fish communities after the implementation of the “10-year fishing ban” policy in the Chishui River. We recommend integrating acoustic methods into routine fish resource monitoring.
Seasonal hydroacoustic surveys, combined with net fishing data, were used to investigate the spatiotemporal distribution of fish resources in the lower Chishui River during 2023. The results showed that fish communities were primarily composed of Squalidus argentatus, Pelteobagrus vachelli, and Pseudobrama simoni, with notable seasonal variations in composition and abundance. Hydroacoustic results showed that the target strength (TS) of fish individuals exhibited a temporal pattern of February>October>June>August, while density peaked in June (June>August>October>February). Horizontal distribution showed higher densities near the Zhenlong Town, Xianshi Town, and Fuxing Town, with average densities of 16.12 ind/1000m3, 21.16 ind/1000m3, and 17.46 ind/1000m3, respectively. In terms of vertical distribution, the fish density is primarily concentrated in the lower layers. Geostatistical analysis estimated seasonal fish resources ranging from 2.94×105 (winter) to 1.72×106 (spring), exhibiting a patchy distribution related to water depth and channel morphology. Compared to historical data, our results indicated an initial recovery of fish communities after the implementation of the “10-year fishing ban” policy in the Chishui River. We recommend integrating acoustic methods into routine fish resource monitoring.
2026,(2):000-000, DOI: 10.18307/2026.0254
Available online: August 28, 2025
Abstract:
Reservoirs constitute significant sources of greenhouse gas emissions. To investigate the spatiotemporal variations and driving factors of dissolved greenhouse gas concentrations and diffusive fluxes in cascade reservoirs, this study focused on the Gangnan and Huangbizhuang reservoirs located along the mainstem of Hutuo River in Hebei Province. Two field campaigns were conducted during the drainage period (2023) and storage period (2023), employing headspace equilibrium method to measure dissolved concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), while diffusive fluxes across water-air interface were estimated using diffusion models. Concurrent measurements of water column and sediment physicochemical parameters were performed. Results showed mean dissolved concentrations of 442.16±159.64 μmol/L for CO2, 0.30±0.26 μmol/L for CH4, and 0.04±0.02 μmol/L for N2O, with corresponding fluxes of 63.26±69.43 mmol/(m2·d), 42.02±49.89 μmol/(m2·d), and 3.58±3.54 μmol/(m2·d). Temporally, dissolved concentrations and diffusive fluxes of CO2 and CH4, along with N2O fluxes, were generally higher during drainage than storage, whereas N2O concentrations exhibited the opposite trend. Spatially, during drainage, CO2 concentrations and fluxes were greater in Gangnan Reservoir than Huangbizhuang Reservoir, while CH4 and N2O showed higher values in Huangbizhuang Reservoir. During storage, all three greenhouse gases exhibited elevated concentrations and fluxes in riverine zones and Huangbizhuang Reservoir compared to Gangnan Reservoir. Redundancy analysis revealed that during drainage, conductivity, dissolved oxygen, and sediment NH4+-N were key factors regulating dissolved gas concentrations, whereas conductivity and sediment pH primarily influenced diffusive fluxes. During storage, water pH and NH4+-N controlled dissolved concentrations, while dissolved oxygen and suspended particulate matter governed flux variations, indicating co-regulation of reservoir greenhouse gases by both water column and sediment properties. Comparative analysis with national averages demonstrated that Gangnan and Huangbizhuang reservoirs exhibit distinct emission patterns: elevated CO2 fluxes but relatively low CH4 and N2O emissions.
Reservoirs constitute significant sources of greenhouse gas emissions. To investigate the spatiotemporal variations and driving factors of dissolved greenhouse gas concentrations and diffusive fluxes in cascade reservoirs, this study focused on the Gangnan and Huangbizhuang reservoirs located along the mainstem of Hutuo River in Hebei Province. Two field campaigns were conducted during the drainage period (2023) and storage period (2023), employing headspace equilibrium method to measure dissolved concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), while diffusive fluxes across water-air interface were estimated using diffusion models. Concurrent measurements of water column and sediment physicochemical parameters were performed. Results showed mean dissolved concentrations of 442.16±159.64 μmol/L for CO2, 0.30±0.26 μmol/L for CH4, and 0.04±0.02 μmol/L for N2O, with corresponding fluxes of 63.26±69.43 mmol/(m2·d), 42.02±49.89 μmol/(m2·d), and 3.58±3.54 μmol/(m2·d). Temporally, dissolved concentrations and diffusive fluxes of CO2 and CH4, along with N2O fluxes, were generally higher during drainage than storage, whereas N2O concentrations exhibited the opposite trend. Spatially, during drainage, CO2 concentrations and fluxes were greater in Gangnan Reservoir than Huangbizhuang Reservoir, while CH4 and N2O showed higher values in Huangbizhuang Reservoir. During storage, all three greenhouse gases exhibited elevated concentrations and fluxes in riverine zones and Huangbizhuang Reservoir compared to Gangnan Reservoir. Redundancy analysis revealed that during drainage, conductivity, dissolved oxygen, and sediment NH4+-N were key factors regulating dissolved gas concentrations, whereas conductivity and sediment pH primarily influenced diffusive fluxes. During storage, water pH and NH4+-N controlled dissolved concentrations, while dissolved oxygen and suspended particulate matter governed flux variations, indicating co-regulation of reservoir greenhouse gases by both water column and sediment properties. Comparative analysis with national averages demonstrated that Gangnan and Huangbizhuang reservoirs exhibit distinct emission patterns: elevated CO2 fluxes but relatively low CH4 and N2O emissions.
2026,(2):000-000, DOI: 10.18307/2026.0229
Available online: August 28, 2025
Abstract:
The source of Yangtze River and Lancang River are important water sources and natural barriers of aquatic ecosystems in the lower part of the river basin. In recent years, the ecosystems and habitats of the two source areas are facing great challenges in terms of ecosystems and habitats protection, driven by the superimposed effects of climate change and human activities. Chromophoric dissolved organic matter (CDOM), as an important component of aquatic ecosystems, plays an important role in revealing the changes and responses of aquatic ecosystems. Therefore, in this study, the spectral characteristics of CDOM in the main streams and tributaries of the Yangtze River and Lancang River during the ice-melting and water-abundance periods were systematically explored by combining ultraviolet-visible (UV-Vis) spectroscopy and 3D fluorescence spectroscopy, revealing the compositional characteristics, sources and differences of CDOM in the two source areas, aiming to provide scientific basis for revealing the carbon cycle, the migration and transformation process of organic matter in the hinterland of the Tibetan Plateau, as well as for evaluating the degree of human influence in the source areas. The results showed that 1) the absorption coefficients α254 and DOC in the Yangtze River and Lancang River sources during the ice ablation period were higher than those in the abundant water period, and the spectral parameters E2/E3 and SUVA254 indicated that the degree of humification, aromaticity, and the relative molecular mass of CDOM in the two source regions were higher overall, and all of them showed the characteristics of a strong land source of organic matter. 2) A total of eight fluorescence fractions were extracted from the two source areas, all of which were dominated by land-source-like humic substances. Among them, the CJ-C1 (260nm/500nm) and CJ-C4 (290nm/400nm), CJ-C2 (260nm/420nm) and CJ-C3 (350nm/450nm) fractions of the Yangtze River source were UVA-like humic substances, humic substances, and UVC-like humic substances, and were mainly dominated by the CJ-C2 (36.4%) and CJ-C4 ( 24.4%) fractions; LCJ-C1 (255nm/480nm), LCJ-C2 (255nm/400nm) and LCJ-C3 (330nm/440nm) of the Lancang River source were UVA-like humic substances, humic substances and UVC-like humic substances, respectively (a total of 83.4%), and LCJ-C4 (280nm/355nm) was a humic substance like tryptophan (16.6%), indicating that the CDOM composition of the Lancang River source was also affected by human activities. 3) The mean values of fluorescence index (FI) and autochthonous index (BIX) of the Yangtze River source were 1.36 and 0.26, respectively, which were lower than those of the Lancang River source (the mean value of FI was 1.45, and the mean value of HIX was 0.52), which indicated that the terrestrial humus characteristics of the CDOM of the Yangtze River source were higher than those of the Lancang River source; the CDOM of the two source areas were mainly derived from the organic matter produced by terrestrial water and soil erosion or through atmospheric deposition and burial in glacial permafrost. The CDOM of both source areas is mainly derived from the organic matter produced by land soil erosion or buried in glacial permafrost through at`1mospheric deposition, but the CDOM of the Lancang River source is also affected by the input of organic matter from agriculture and livestock in the basin.
The source of Yangtze River and Lancang River are important water sources and natural barriers of aquatic ecosystems in the lower part of the river basin. In recent years, the ecosystems and habitats of the two source areas are facing great challenges in terms of ecosystems and habitats protection, driven by the superimposed effects of climate change and human activities. Chromophoric dissolved organic matter (CDOM), as an important component of aquatic ecosystems, plays an important role in revealing the changes and responses of aquatic ecosystems. Therefore, in this study, the spectral characteristics of CDOM in the main streams and tributaries of the Yangtze River and Lancang River during the ice-melting and water-abundance periods were systematically explored by combining ultraviolet-visible (UV-Vis) spectroscopy and 3D fluorescence spectroscopy, revealing the compositional characteristics, sources and differences of CDOM in the two source areas, aiming to provide scientific basis for revealing the carbon cycle, the migration and transformation process of organic matter in the hinterland of the Tibetan Plateau, as well as for evaluating the degree of human influence in the source areas. The results showed that 1) the absorption coefficients α254 and DOC in the Yangtze River and Lancang River sources during the ice ablation period were higher than those in the abundant water period, and the spectral parameters E2/E3 and SUVA254 indicated that the degree of humification, aromaticity, and the relative molecular mass of CDOM in the two source regions were higher overall, and all of them showed the characteristics of a strong land source of organic matter. 2) A total of eight fluorescence fractions were extracted from the two source areas, all of which were dominated by land-source-like humic substances. Among them, the CJ-C1 (260nm/500nm) and CJ-C4 (290nm/400nm), CJ-C2 (260nm/420nm) and CJ-C3 (350nm/450nm) fractions of the Yangtze River source were UVA-like humic substances, humic substances, and UVC-like humic substances, and were mainly dominated by the CJ-C2 (36.4%) and CJ-C4 ( 24.4%) fractions; LCJ-C1 (255nm/480nm), LCJ-C2 (255nm/400nm) and LCJ-C3 (330nm/440nm) of the Lancang River source were UVA-like humic substances, humic substances and UVC-like humic substances, respectively (a total of 83.4%), and LCJ-C4 (280nm/355nm) was a humic substance like tryptophan (16.6%), indicating that the CDOM composition of the Lancang River source was also affected by human activities. 3) The mean values of fluorescence index (FI) and autochthonous index (BIX) of the Yangtze River source were 1.36 and 0.26, respectively, which were lower than those of the Lancang River source (the mean value of FI was 1.45, and the mean value of HIX was 0.52), which indicated that the terrestrial humus characteristics of the CDOM of the Yangtze River source were higher than those of the Lancang River source; the CDOM of the two source areas were mainly derived from the organic matter produced by terrestrial water and soil erosion or through atmospheric deposition and burial in glacial permafrost. The CDOM of both source areas is mainly derived from the organic matter produced by land soil erosion or buried in glacial permafrost through at`1mospheric deposition, but the CDOM of the Lancang River source is also affected by the input of organic matter from agriculture and livestock in the basin.
2026,(2):000-000, DOI: 10.18307/2026.0202
Available online: August 28, 2025
Abstract:
Nitrogen fixation is critical for primary productivity and carbon-nitrogen biogeochemical cycles in marine, riverine, and lacustrine ecosystems. However, research on aquatic nitrogen fixation remains predominantly focused on marine environments. To elucidate research hotspots and trends in freshwater lake nitrogen-fixing microorganisms, this study analyzed literature from the Web of Science database using Citespace and VOSviewer to construct a knowledge map of publication trends and thematic evolution. Results indicate a continuous increase in global publications and citations from 1992 to 2024, with collaborative networks revealing interdisciplinary and multinational research engagement. Cluster analysis identified three core research foci: (1) phosphorus limitation-driven nutrient control strategies and their impacts on cyanobacterial community succession (Cluster 0), (2) functional characterization of nitrogen-fixing microorganisms based onSnifHSgene diversity (Cluster 1), and (3) long-term phytoplankton community dynamics under environmental drivers (Cluster 2). Meta-analysis further revealed: (1) Geographical imbalance in nitrogen fixation quantification, with North America establishing comprehensive indicator systems across diverse water bodies, while Asia and South America prioritize cyanobacterial biomass descriptions, and Europe focuses on regional nitrogen-phosphorus dynamics; (2) Dominance of Cyanobacteria (e.g.,SDolichospermum,SAphanizomenon) in taxonomic studies, with limited research on Proteobacteria and Archaea; (3) Positive correlation between total phosphorus (TP) and nitrogen fixation rates, with a nonlinear threshold (24.97 μg-P/L) regulating fixation in eutrophic systems, while total dissolved nitrogen (TDN), nitrate (NO??-N), and ammonium (NH??-N) exhibit significant negative correlations. Future research should prioritize diversification of measurement indicators (e.g., fixation rates, enzyme activity) to capture niche-specific processes, standardization of methodologies (e.g., acetylene reduction assay, isotopic tracer techniques) and unit systems (area/volume-based metrics), and integration of multi-indicator approaches to enhance accuracy in assessing nitrogen fixation roles. This study synthesizes three decades of research trends, providing insights into frontier topics and guiding future research directions.Keywords: freshwater lakes; nitrogen-fixing microorganisms; Citespace; keyword clustering; research hotspots; nitrogen and phosphorus
Nitrogen fixation is critical for primary productivity and carbon-nitrogen biogeochemical cycles in marine, riverine, and lacustrine ecosystems. However, research on aquatic nitrogen fixation remains predominantly focused on marine environments. To elucidate research hotspots and trends in freshwater lake nitrogen-fixing microorganisms, this study analyzed literature from the Web of Science database using Citespace and VOSviewer to construct a knowledge map of publication trends and thematic evolution. Results indicate a continuous increase in global publications and citations from 1992 to 2024, with collaborative networks revealing interdisciplinary and multinational research engagement. Cluster analysis identified three core research foci: (1) phosphorus limitation-driven nutrient control strategies and their impacts on cyanobacterial community succession (Cluster 0), (2) functional characterization of nitrogen-fixing microorganisms based onSnifHSgene diversity (Cluster 1), and (3) long-term phytoplankton community dynamics under environmental drivers (Cluster 2). Meta-analysis further revealed: (1) Geographical imbalance in nitrogen fixation quantification, with North America establishing comprehensive indicator systems across diverse water bodies, while Asia and South America prioritize cyanobacterial biomass descriptions, and Europe focuses on regional nitrogen-phosphorus dynamics; (2) Dominance of Cyanobacteria (e.g.,SDolichospermum,SAphanizomenon) in taxonomic studies, with limited research on Proteobacteria and Archaea; (3) Positive correlation between total phosphorus (TP) and nitrogen fixation rates, with a nonlinear threshold (24.97 μg-P/L) regulating fixation in eutrophic systems, while total dissolved nitrogen (TDN), nitrate (NO??-N), and ammonium (NH??-N) exhibit significant negative correlations. Future research should prioritize diversification of measurement indicators (e.g., fixation rates, enzyme activity) to capture niche-specific processes, standardization of methodologies (e.g., acetylene reduction assay, isotopic tracer techniques) and unit systems (area/volume-based metrics), and integration of multi-indicator approaches to enhance accuracy in assessing nitrogen fixation roles. This study synthesizes three decades of research trends, providing insights into frontier topics and guiding future research directions.Keywords: freshwater lakes; nitrogen-fixing microorganisms; Citespace; keyword clustering; research hotspots; nitrogen and phosphorus
2026,(2):000-000, DOI: 10.18307/2026.0226
Available online: August 28, 2025
Abstract:
Seasonal temperature changes have significantly affected microbial functional transformations and greenhouse gas emissions in ecosystems. Current studies have shown that there is a direct regulatory effect of temperature on microorganisms in plant-free systems. The lakeshore zone, as an important site for climate change response, is characterized by periodic water-level fluctuations that place sediments under different flooding conditions, profoundly affecting the sediment microenvironment and microbial activity. However, the effects of temperature on functional microorganisms in lakeshore sediments with different flooding conditions have not been well studied. In this study, we investigated the short-term effects of temperature on microbial denitrification in lakeshore sediments by simulating four types of flooding conditions, including non-flooded (NF), intermittent flooded (IF), alternating high and low water level flooded (HLF), and constant water level flooded (WF). The results showed that increasing temperature significantly increased the sediment N2 release rate and decreased the N2O release rate under each flooding condition. In terms of microbial metabolism, the effect of temperature on carbon metabolic pathways was variable: under NF and IF conditions, 15°C promoted glycolysis and pentose phosphate cycle activities, while 30°C produced inhibition; while under HLF and WF conditions, 30°C significantly activated different carbon metabolic activities. Meanwhile, the content of electron donors was inhibited by 30°C under NF and IF conditions, but significantly increased under HLF and WF conditions. Notably, temperature altered the electron-consuming capacity by modulating the activity of denitrification key enzymes, resulting in an increase in the N2 potential release rate and a decrease in the N2O potential release rate. In terms of microbial communities, temperature significantly altered the diversity and compositional characteristics of nirS and nosZ-type denitrifying bacteria in lakeshore sediments under different flooding conditions. Further analysis by partial least squares path modeling indicated that the community of nirS and nosZ-type denitrifying bacteria was a key indicator for predicting the potential release rates of N2 and N2O at different temperatures compared to the metabolic processes of microorganisms. In addition, by estimating the potential emissions of N2 and N2O from sediments in the lakeshore zone, it was found that sediments in the area of frequent water level fluctuations in the lakeshore zone have a better nitrogen removal capacity under high temperature (30℃) environments, which is a key spatial and temporal point for the conversion of greenhouse gases to the environmentally friendly end-product N2.
Seasonal temperature changes have significantly affected microbial functional transformations and greenhouse gas emissions in ecosystems. Current studies have shown that there is a direct regulatory effect of temperature on microorganisms in plant-free systems. The lakeshore zone, as an important site for climate change response, is characterized by periodic water-level fluctuations that place sediments under different flooding conditions, profoundly affecting the sediment microenvironment and microbial activity. However, the effects of temperature on functional microorganisms in lakeshore sediments with different flooding conditions have not been well studied. In this study, we investigated the short-term effects of temperature on microbial denitrification in lakeshore sediments by simulating four types of flooding conditions, including non-flooded (NF), intermittent flooded (IF), alternating high and low water level flooded (HLF), and constant water level flooded (WF). The results showed that increasing temperature significantly increased the sediment N2 release rate and decreased the N2O release rate under each flooding condition. In terms of microbial metabolism, the effect of temperature on carbon metabolic pathways was variable: under NF and IF conditions, 15°C promoted glycolysis and pentose phosphate cycle activities, while 30°C produced inhibition; while under HLF and WF conditions, 30°C significantly activated different carbon metabolic activities. Meanwhile, the content of electron donors was inhibited by 30°C under NF and IF conditions, but significantly increased under HLF and WF conditions. Notably, temperature altered the electron-consuming capacity by modulating the activity of denitrification key enzymes, resulting in an increase in the N2 potential release rate and a decrease in the N2O potential release rate. In terms of microbial communities, temperature significantly altered the diversity and compositional characteristics of nirS and nosZ-type denitrifying bacteria in lakeshore sediments under different flooding conditions. Further analysis by partial least squares path modeling indicated that the community of nirS and nosZ-type denitrifying bacteria was a key indicator for predicting the potential release rates of N2 and N2O at different temperatures compared to the metabolic processes of microorganisms. In addition, by estimating the potential emissions of N2 and N2O from sediments in the lakeshore zone, it was found that sediments in the area of frequent water level fluctuations in the lakeshore zone have a better nitrogen removal capacity under high temperature (30℃) environments, which is a key spatial and temporal point for the conversion of greenhouse gases to the environmentally friendly end-product N2.
zhongxiang, xiongqiulin, nieyunju, chenwenbo, liujutao, yangping, xuligang, huangyirong, hongqingwen, gaobeijie
2026,(2):000-000, DOI: 10.18307/2026.0223
Available online: August 28, 2025
Abstract:
In August 2021 (wet season), 45 sampling sites were established across the Poyang Lake area. The concentrations of Mn, Cu, Zn, Cd, Pb, Cr, As and Hg in the lake water were analyzed using Inductively Coupled Plasma Mass Spectrometry and Atomic Fluorescence Spectrometry. Human health risk assessment for heavy metals was conducted based on drinking water and dermal exposure parameters specific to the Chinese population. Spatial distribution characteristics of heavy metals and their associated health risks were analyzed using the Kriging interpolation method. Key results indicate: (1) The concentration of heavy metals in the study area ranged from 1.89 μg/L to 183.25 μg/L, with Mn exhibiting the highest average concentration and Cr the lowest. Elevated heavy metal concentrations were observed in the river-lake ecotone in the southern Poyang Lake, where Mn levels exceeded safety standards at the confluences of Poyang Lake with the Ganjiang, Xinjiang, and Fuhe rivers. (2) As and Cr posed significant human health risks in Poyang Lake. In 2021, carcinogenic risk dominated the heavy metal risks in the lake water, with As presenting a pronounced carcinogenic threat. Some sampling sites showed low non-carcinogenic risks for Cr. (3) High non-carcinogenic risk areas were primarily distributed in the southern lake region, while high carcinogenic risk areas were concentrated in the central lake region. Mn, As, and Cr are the heavy metals that need to be strictly controlled in Poyang Lake. The water pollution caused by heavy metals in the southern and central parts of the lake area should be given priority for prevention and control.
In August 2021 (wet season), 45 sampling sites were established across the Poyang Lake area. The concentrations of Mn, Cu, Zn, Cd, Pb, Cr, As and Hg in the lake water were analyzed using Inductively Coupled Plasma Mass Spectrometry and Atomic Fluorescence Spectrometry. Human health risk assessment for heavy metals was conducted based on drinking water and dermal exposure parameters specific to the Chinese population. Spatial distribution characteristics of heavy metals and their associated health risks were analyzed using the Kriging interpolation method. Key results indicate: (1) The concentration of heavy metals in the study area ranged from 1.89 μg/L to 183.25 μg/L, with Mn exhibiting the highest average concentration and Cr the lowest. Elevated heavy metal concentrations were observed in the river-lake ecotone in the southern Poyang Lake, where Mn levels exceeded safety standards at the confluences of Poyang Lake with the Ganjiang, Xinjiang, and Fuhe rivers. (2) As and Cr posed significant human health risks in Poyang Lake. In 2021, carcinogenic risk dominated the heavy metal risks in the lake water, with As presenting a pronounced carcinogenic threat. Some sampling sites showed low non-carcinogenic risks for Cr. (3) High non-carcinogenic risk areas were primarily distributed in the southern lake region, while high carcinogenic risk areas were concentrated in the central lake region. Mn, As, and Cr are the heavy metals that need to be strictly controlled in Poyang Lake. The water pollution caused by heavy metals in the southern and central parts of the lake area should be given priority for prevention and control.
2026,(2):000-000, DOI: 10.18307/2026.0233
Available online: August 28, 2025
Abstract:
Bacterioplankton are an important part of freshwater ecosystems such as rivers. To explore the seasonal dynamics and driving mechanisms of bacterioplankton communities in the river of the southeastern Himalayan basin, we used 16S rRNA high-throughput sequencing technology to analyze the diversity, biogeographical patterns and driving factors of bacterioplankton communities at 33 different sites in the river of the southeastern Himalayan basin in terms of time scale in spring (May), summer (July) and autumn (September). The results showed that: (1) Proteobacteria, Actinobacteriota, Bacteroidota and Cyanobacteria were the dominant phyla in all three seasons. The abundance of Proteobacteria was the highest, with a seasonal difference of spring > autumn > summer. The Shannon diversity index, Simpson diversity index and Chao1 diversity index of bacterioplankton communities in spring were the lowest, and the difference was significant compared with those. (2) There were significant differences among the bacterioplankton communities in the three seasons. β diversity and component decomposition showed that the differences in the three seasons were mainly driven by species turnover. There was a significant trend of geographic distance attenuation in each season, and the decline rate was the fastest in autumn. (3) The Neutral Community Model and the Modified Stochasticity Ratio showed that the stochastic process dominated the assembly of the bacterioplankton communities in spring, while the deterministic process dominated in summer and autumn. (4) The co-occurrence network analysis showed that the species interactions between bacterioplankton communities in the three seasons was dominated by synergistic effect, and each network exhibited a high degree of modularity. (5) Compared to geographical factors, the bacterioplankton communities are more influenced by environmental factors. The key driving factors affecting the bacterioplankton communities in spring are EC, COD, TN, ALT and DO, while in summer they are TUR, EC and pH. In autumn, TUR, ALT, DO, EC and WT are considered. The results show that the bacterioplankton communities in the river of the southeastern Himalayan basin are driven by geographical distance, species interaction and different environmental factors, and there are seasonal differences.
Bacterioplankton are an important part of freshwater ecosystems such as rivers. To explore the seasonal dynamics and driving mechanisms of bacterioplankton communities in the river of the southeastern Himalayan basin, we used 16S rRNA high-throughput sequencing technology to analyze the diversity, biogeographical patterns and driving factors of bacterioplankton communities at 33 different sites in the river of the southeastern Himalayan basin in terms of time scale in spring (May), summer (July) and autumn (September). The results showed that: (1) Proteobacteria, Actinobacteriota, Bacteroidota and Cyanobacteria were the dominant phyla in all three seasons. The abundance of Proteobacteria was the highest, with a seasonal difference of spring > autumn > summer. The Shannon diversity index, Simpson diversity index and Chao1 diversity index of bacterioplankton communities in spring were the lowest, and the difference was significant compared with those. (2) There were significant differences among the bacterioplankton communities in the three seasons. β diversity and component decomposition showed that the differences in the three seasons were mainly driven by species turnover. There was a significant trend of geographic distance attenuation in each season, and the decline rate was the fastest in autumn. (3) The Neutral Community Model and the Modified Stochasticity Ratio showed that the stochastic process dominated the assembly of the bacterioplankton communities in spring, while the deterministic process dominated in summer and autumn. (4) The co-occurrence network analysis showed that the species interactions between bacterioplankton communities in the three seasons was dominated by synergistic effect, and each network exhibited a high degree of modularity. (5) Compared to geographical factors, the bacterioplankton communities are more influenced by environmental factors. The key driving factors affecting the bacterioplankton communities in spring are EC, COD, TN, ALT and DO, while in summer they are TUR, EC and pH. In autumn, TUR, ALT, DO, EC and WT are considered. The results show that the bacterioplankton communities in the river of the southeastern Himalayan basin are driven by geographical distance, species interaction and different environmental factors, and there are seasonal differences.
2026,(2):000-000, DOI: 10.18307/2026.0201
Available online: August 21, 2025
Abstract:
As emerging environmental contaminants, antibiotic resistance genes (ARGs) and their transmission mechanisms and risk control in basin water environments represent critical scientific issues for ensuring water security. This paper systematically reviews the occurrence characteristics, pollution sources, and spatiotemporal distribution patterns of ARGs in the water environments of China’s seven major river basins (Yangtze River, Yellow River, Huaihe River, Pearl River, Haihe River, Liaohe River, and Songhua River). It also analyzes the migration and diffusion mechanisms of ARGs in combination with the combined pollution effects of eutrophication, heavy metals, and emerging contaminants (antibiotics, microplastics, endocrine-disrupting chemicals, persistent organic pollutants, etc.). The study shows that ARGs in China’s basin water environments are dominated by sulfonamides, tetracyclines, and aminoglycosides, primarily sourced from non-point source pollution (agricultural planting, livestock and poultry farming, etc.) and point source emissions (wastewater treatment plant effluents, medical wastewater, etc.). In terms of occurrence levels, the absolute abundances of ARGs in sediments (106~1010 copies/g) are generally three orders of magnitude higher than those in water bodies (103~107 copies/mL), though their relative abundances (copies/16S rRNA) are similar. Spatiotemporally, ARGs are driven by microbial communities, environmental physicochemical factors, human activities, and mobile genetic elements (MGEs), with microbial communities exerting the most significant influence. Regarding pollution effects, water eutrophication promotes the proliferation of ARG-hosting bacterial communities such as nitrate-reducing bacteria, resulting in a significant positive correlation between ARG abundances and total nitrogen (TN) and total phosphorus (TP) loads. Heavy metals (e.g., Cu, Zn, Ni) enhance ARG conjugative transfer efficiency through co-selection effects. Among emerging contaminants, antibiotics drive ARG evolution through selective pressure; microplastic biofilms can increase ARG transformation frequencies to 1,000 times those of natural substrates; and endocrine-disrupting chemicals (e.g., bisphenol A) and persistent organic pollutants (e.g., perfluorooctanoic acid) promote ARG horizontal transfer by inducing oxidative stress or upregulating plasmid expression. ARG transmission mechanisms primarily include bacterial community shaping (e.g., selective enrichment of Firmicutes and Proteobacteria), conjugative transfer (dependent on MGEs and ATP energy metabolism), induced transformation (extracellular eDNA adsorption onto suspended particulates), and phage-mediated transfer (preferential packaging of ARG fragments). Notably, fluvial sediment dynamics processes, such as suspended sediment transport and sediment resuspension, significantly influence ARG transmission fluxes by regulating pollutant partitioning across phases. Future research should investigate the coupled processes of "sediment-water dynamics-contaminants-ARGs," analyze cross-scale regulatory mechanisms of ARGs in multi-phase water environments, and explore the application potential of sediment-water ecological regulation in ARG risk management.
As emerging environmental contaminants, antibiotic resistance genes (ARGs) and their transmission mechanisms and risk control in basin water environments represent critical scientific issues for ensuring water security. This paper systematically reviews the occurrence characteristics, pollution sources, and spatiotemporal distribution patterns of ARGs in the water environments of China’s seven major river basins (Yangtze River, Yellow River, Huaihe River, Pearl River, Haihe River, Liaohe River, and Songhua River). It also analyzes the migration and diffusion mechanisms of ARGs in combination with the combined pollution effects of eutrophication, heavy metals, and emerging contaminants (antibiotics, microplastics, endocrine-disrupting chemicals, persistent organic pollutants, etc.). The study shows that ARGs in China’s basin water environments are dominated by sulfonamides, tetracyclines, and aminoglycosides, primarily sourced from non-point source pollution (agricultural planting, livestock and poultry farming, etc.) and point source emissions (wastewater treatment plant effluents, medical wastewater, etc.). In terms of occurrence levels, the absolute abundances of ARGs in sediments (106~1010 copies/g) are generally three orders of magnitude higher than those in water bodies (103~107 copies/mL), though their relative abundances (copies/16S rRNA) are similar. Spatiotemporally, ARGs are driven by microbial communities, environmental physicochemical factors, human activities, and mobile genetic elements (MGEs), with microbial communities exerting the most significant influence. Regarding pollution effects, water eutrophication promotes the proliferation of ARG-hosting bacterial communities such as nitrate-reducing bacteria, resulting in a significant positive correlation between ARG abundances and total nitrogen (TN) and total phosphorus (TP) loads. Heavy metals (e.g., Cu, Zn, Ni) enhance ARG conjugative transfer efficiency through co-selection effects. Among emerging contaminants, antibiotics drive ARG evolution through selective pressure; microplastic biofilms can increase ARG transformation frequencies to 1,000 times those of natural substrates; and endocrine-disrupting chemicals (e.g., bisphenol A) and persistent organic pollutants (e.g., perfluorooctanoic acid) promote ARG horizontal transfer by inducing oxidative stress or upregulating plasmid expression. ARG transmission mechanisms primarily include bacterial community shaping (e.g., selective enrichment of Firmicutes and Proteobacteria), conjugative transfer (dependent on MGEs and ATP energy metabolism), induced transformation (extracellular eDNA adsorption onto suspended particulates), and phage-mediated transfer (preferential packaging of ARG fragments). Notably, fluvial sediment dynamics processes, such as suspended sediment transport and sediment resuspension, significantly influence ARG transmission fluxes by regulating pollutant partitioning across phases. Future research should investigate the coupled processes of "sediment-water dynamics-contaminants-ARGs," analyze cross-scale regulatory mechanisms of ARGs in multi-phase water environments, and explore the application potential of sediment-water ecological regulation in ARG risk management.
Huang Yanan, Yang Zhengjian, Han Yanxing, Guo Xiaojuan, Ji Daobin, Cui Yujie, Li Yiping, Liu Defu, Wang Congfeng
2026,(2):000-000, DOI: 10.18307/2026.0227
Available online: August 21, 2025
Abstract:
Denitrification is a crucial process for removing nitrogen loads from aquatic ecosystems. To assess the impacts of algae in reservoirs on water denitrification, we selected the Xiangxi Bay (XXB), a typical tributary of the Three Gorges Reservoir (TGR). In situ water samples were collected, and experiments were conducted to assess the denitrification potential of algae with different concentrations, species, and growth conditions. The acetylene inhibition method was used to measure the denitrification rate. The results indicated that within a specific concentration range, the water column denitrification rate increased with rising algal concentrations. However, when the algal concentration reached four times the baseline level (with a Chl-a concentration of 472.1 μg·L-1), the denitrification rate declined due to limitations in nitrate substrate availability. The smaller cell size and cell number of added Microcystis aeruginosa may account for the slightly lower denitrification rate compared to Chlorella pyrenoidosa. The denitrification rates in water with the addition of decaying algae were consistently higher than those in the growing group. Specifically, decaying Microcystis aeruginosa (42.50±1.26 nmol·L-1·h-1) significantly promoted denitrification more than decaying Chlorella pyrenoidosa (29.02 ±0.10 nmol·L?1·h?1). This enhancement is primarily due to the fact that decaying algae, at suitable concentrations, can provide essential carbon and nitrogen substrates, as well as a more favorable dissolved oxygen environment. Further research is needed to determine the optimal concentration of growing algae, and community structure that is most beneficial for water denitrification in tributaries of the TGR. While controlling algal blooms through methods such as water level fluctuations, it is also crucial to consider enhancing algal-mediated denitrification. This approach will provide a theoretical basis for accurately assessing the denitrification effects of reservoirs and optimizing reservoir operations to promote denitrification functions.
Denitrification is a crucial process for removing nitrogen loads from aquatic ecosystems. To assess the impacts of algae in reservoirs on water denitrification, we selected the Xiangxi Bay (XXB), a typical tributary of the Three Gorges Reservoir (TGR). In situ water samples were collected, and experiments were conducted to assess the denitrification potential of algae with different concentrations, species, and growth conditions. The acetylene inhibition method was used to measure the denitrification rate. The results indicated that within a specific concentration range, the water column denitrification rate increased with rising algal concentrations. However, when the algal concentration reached four times the baseline level (with a Chl-a concentration of 472.1 μg·L-1), the denitrification rate declined due to limitations in nitrate substrate availability. The smaller cell size and cell number of added Microcystis aeruginosa may account for the slightly lower denitrification rate compared to Chlorella pyrenoidosa. The denitrification rates in water with the addition of decaying algae were consistently higher than those in the growing group. Specifically, decaying Microcystis aeruginosa (42.50±1.26 nmol·L-1·h-1) significantly promoted denitrification more than decaying Chlorella pyrenoidosa (29.02 ±0.10 nmol·L?1·h?1). This enhancement is primarily due to the fact that decaying algae, at suitable concentrations, can provide essential carbon and nitrogen substrates, as well as a more favorable dissolved oxygen environment. Further research is needed to determine the optimal concentration of growing algae, and community structure that is most beneficial for water denitrification in tributaries of the TGR. While controlling algal blooms through methods such as water level fluctuations, it is also crucial to consider enhancing algal-mediated denitrification. This approach will provide a theoretical basis for accurately assessing the denitrification effects of reservoirs and optimizing reservoir operations to promote denitrification functions.
2026,(2):000-000, DOI: 10.18307/2026.0228
Available online: August 21, 2025
Abstract:
Denitrification is an important pathway for removing nitrogen loads from water bodies. Accurately and rapidly measuring the denitrification rate in water bodies is crucial for assessing the nitrogen removal potential of lakes, reservoirs, and rivers. To address the issues of existing methods, such as the acetylene inhibition method and the 15N isotope tracer method, which are unable to provide in situ rapid measurements of denitrification rates, and are costly and time-consuming, this study proposes a novel method for rapid in situ measurement of denitrification rates in water bodies based on nitrogen gas increment. The method involves in situ water sampling, purging, incubation, and measurement, enabling rapid field detection of total denitrification rates. This method was applied in May–June 2024 to conduct point-based continuous monitoring and bay-wide surveys of denitrification rates in the Pengxi River, a tributary of the Three Gorges Reservoir. A comparison with the acetylene inhibition method was performed, and the influence of various environmental factors on denitrification rates was analyzed. Results showed that the denitrification rates measured by this method were approximately seven times higher than the denitrification rates obtained using the acetylene inhibition method, with a significant correlation between the two. During the monitoring period, the denitrification rates in the Pengxi River were highest in the surface layer, followed by the bottom layer and then the middle layer. The surface layer denitrification rates were mainly influenced by algal concentrations, while those in the bottom layer were primarily affected by turbidity. This study has significant implications for the rapid in situ measurement of water body denitrification rates and for accurately understanding and evaluating the nitrogen removal potential of water bodies.
Denitrification is an important pathway for removing nitrogen loads from water bodies. Accurately and rapidly measuring the denitrification rate in water bodies is crucial for assessing the nitrogen removal potential of lakes, reservoirs, and rivers. To address the issues of existing methods, such as the acetylene inhibition method and the 15N isotope tracer method, which are unable to provide in situ rapid measurements of denitrification rates, and are costly and time-consuming, this study proposes a novel method for rapid in situ measurement of denitrification rates in water bodies based on nitrogen gas increment. The method involves in situ water sampling, purging, incubation, and measurement, enabling rapid field detection of total denitrification rates. This method was applied in May–June 2024 to conduct point-based continuous monitoring and bay-wide surveys of denitrification rates in the Pengxi River, a tributary of the Three Gorges Reservoir. A comparison with the acetylene inhibition method was performed, and the influence of various environmental factors on denitrification rates was analyzed. Results showed that the denitrification rates measured by this method were approximately seven times higher than the denitrification rates obtained using the acetylene inhibition method, with a significant correlation between the two. During the monitoring period, the denitrification rates in the Pengxi River were highest in the surface layer, followed by the bottom layer and then the middle layer. The surface layer denitrification rates were mainly influenced by algal concentrations, while those in the bottom layer were primarily affected by turbidity. This study has significant implications for the rapid in situ measurement of water body denitrification rates and for accurately understanding and evaluating the nitrogen removal potential of water bodies.
2026,(1):000-000, DOI: 10.18307/2026.0142
Available online: July 25, 2025
Abstract:
The impact of the "four colliding" typhoons has become the focus of attention in the disaster prevention and reduction system in the Taihu basin. However, the risk impact of wind, storm, tide, and flood brought by it on the safety of flood prevention is still unclear. It is considerable to carry out the analysis of rainstorm, flood and its movement caused by the typical typhoon of "four colliding".It takes the two typical typhoons "Fitow" and "In-Fa" since 1990 as samples, and other typhoons with two or three colliding as references. Based on hydrological and engineering data, the impact of "four colliding" typhoons is compared. The results showed that: (1) The "four colliding" typhoons all caused extreme rainfall, with a large total amount and wide range, resulting in the rainfall that was more than 70% higher than the average of the two and three colliding typhoons. The higher part was basically the same as the rainfall caused by typhoon Morakot in 2009. (2) The water levels of the Taihu Lake has risen by the second and third place respectively since 1949. In particular, "In-Fa" caused numbered floods, and the maximum tilt of the Taihu Lake was more than 1.00 m. The highest water (tide) level of 33 sites in the river network broke the historical records, and the high water levels lasted for a long time, which seriously threatened the safety of regional flood prevention. (3) It was dominated by storage during "Fitow", and then the drainage capacity of backbone projects was significantly enhanced. During "In-Fa", the flood movement pattern changed to both storage and drainage, with the storage and drainage ratio changing from 1:0.6 to 1:1.1, and the proportion of drainage increased. (4) During the rainstorm of the two typhoons, the drainage was obviously restricted by the astronomical spring tide jacking. After the rainfall stopped and the astronomical spring tide passed, the drainage of the backbone projects increased significantly, especially the Yangtze river to the north and the Huangpu river to the east. (5) Although the drainage capacity of the backbone projects has been significantly strengthened, it still needs to be further improved in the face of the "four colliding" typhoon and the transfer of regional flood disaster risks. The research results could provide a reference for the scientific defense of the "four colliding" typhoon in the Taihu basin in the future.
The impact of the "four colliding" typhoons has become the focus of attention in the disaster prevention and reduction system in the Taihu basin. However, the risk impact of wind, storm, tide, and flood brought by it on the safety of flood prevention is still unclear. It is considerable to carry out the analysis of rainstorm, flood and its movement caused by the typical typhoon of "four colliding".It takes the two typical typhoons "Fitow" and "In-Fa" since 1990 as samples, and other typhoons with two or three colliding as references. Based on hydrological and engineering data, the impact of "four colliding" typhoons is compared. The results showed that: (1) The "four colliding" typhoons all caused extreme rainfall, with a large total amount and wide range, resulting in the rainfall that was more than 70% higher than the average of the two and three colliding typhoons. The higher part was basically the same as the rainfall caused by typhoon Morakot in 2009. (2) The water levels of the Taihu Lake has risen by the second and third place respectively since 1949. In particular, "In-Fa" caused numbered floods, and the maximum tilt of the Taihu Lake was more than 1.00 m. The highest water (tide) level of 33 sites in the river network broke the historical records, and the high water levels lasted for a long time, which seriously threatened the safety of regional flood prevention. (3) It was dominated by storage during "Fitow", and then the drainage capacity of backbone projects was significantly enhanced. During "In-Fa", the flood movement pattern changed to both storage and drainage, with the storage and drainage ratio changing from 1:0.6 to 1:1.1, and the proportion of drainage increased. (4) During the rainstorm of the two typhoons, the drainage was obviously restricted by the astronomical spring tide jacking. After the rainfall stopped and the astronomical spring tide passed, the drainage of the backbone projects increased significantly, especially the Yangtze river to the north and the Huangpu river to the east. (5) Although the drainage capacity of the backbone projects has been significantly strengthened, it still needs to be further improved in the face of the "four colliding" typhoon and the transfer of regional flood disaster risks. The research results could provide a reference for the scientific defense of the "four colliding" typhoon in the Taihu basin in the future.
2026,(1):000-000, DOI: 10.18307/2026.0114
Available online: July 25, 2025
Abstract:
In agricultural watersheds across China, small water bodies serve as important phosphorus retention and storage sites, acting as protective barriers for rivers and lakes. However, under conditions of long-term phosphorus accumulation and specific environmental factors, there is a risk of phosphorus release. Currently, there is a lack of research on the phosphorus release risk of small water bodies and on the dynamic changes in phosphorus retention and release, as well as the influencing factors, through long-term experiments. This study focuses on a typical agricultural watershed and conducts sediment sampling from 4 types of ponds, along with a 6-month static incubation experiment. The study analyzes the phosphorus forms in sediments and the phosphorus exchange dynamics at the sediment-water interface, assessing the phosphorus release risk of the ponds and its influencing factors. The results showed that: (1) The total phosphorus (TP) content in pond sediments ranged from 0.55 to 3.02 g/kg, higher than that of other types of wetlands. The highest phosphorus content was found in village ponds, while the lowest was observed in paddy ponds. (2) In agricultural watersheds of the middle and lower reaches of the Yangtze River, and under the condition of long-term existence of ponds, the phosphorus exchange at the sediment-overlying water interface exhibits significant seasonal variations: sediments release phosphorus to the overlying water in summer and autumn, while phosphorus settles from the overlying water to the sediments in autumn and winter. Given similar years of existence, the phosphorus sink capacity of ponds decreases in the following order: forest pond > paddy pond = dryland pond > village pond. This study revealed the large phosphorus accumulation in agricultural ponds in China, highlighting their long-term function as phosphorus sinks that transform into phosphorus sources during the summer and autumn. The findings also clarified the influence of surrounding land use types and provided scientific guidance for improving management strategies for different pond types. These insights are widely applicable to non-point source pollution control and the protection of aquatic environments in rivers and lakes.
In agricultural watersheds across China, small water bodies serve as important phosphorus retention and storage sites, acting as protective barriers for rivers and lakes. However, under conditions of long-term phosphorus accumulation and specific environmental factors, there is a risk of phosphorus release. Currently, there is a lack of research on the phosphorus release risk of small water bodies and on the dynamic changes in phosphorus retention and release, as well as the influencing factors, through long-term experiments. This study focuses on a typical agricultural watershed and conducts sediment sampling from 4 types of ponds, along with a 6-month static incubation experiment. The study analyzes the phosphorus forms in sediments and the phosphorus exchange dynamics at the sediment-water interface, assessing the phosphorus release risk of the ponds and its influencing factors. The results showed that: (1) The total phosphorus (TP) content in pond sediments ranged from 0.55 to 3.02 g/kg, higher than that of other types of wetlands. The highest phosphorus content was found in village ponds, while the lowest was observed in paddy ponds. (2) In agricultural watersheds of the middle and lower reaches of the Yangtze River, and under the condition of long-term existence of ponds, the phosphorus exchange at the sediment-overlying water interface exhibits significant seasonal variations: sediments release phosphorus to the overlying water in summer and autumn, while phosphorus settles from the overlying water to the sediments in autumn and winter. Given similar years of existence, the phosphorus sink capacity of ponds decreases in the following order: forest pond > paddy pond = dryland pond > village pond. This study revealed the large phosphorus accumulation in agricultural ponds in China, highlighting their long-term function as phosphorus sinks that transform into phosphorus sources during the summer and autumn. The findings also clarified the influence of surrounding land use types and provided scientific guidance for improving management strategies for different pond types. These insights are widely applicable to non-point source pollution control and the protection of aquatic environments in rivers and lakes.
2026,(1):000-000, DOI: 10.18307/2026.0135
Available online: July 22, 2025
Abstract:
Poyang Lake, China’s largest freshwater lake, serves as a crucial wintering ground for geese of East Asian. This study employed satellite tracking data from 2019 to 2024 to analyze the migratory phenology and spatial distribution patterns of Greater White-fronted Goose Anser albifrons, Swan Goose Anser cygnoides, and Bean Goose Anser fabalis. By integrating duration and home range data, we quantified the importance of Poyang Lake’s sub-lakes to these species. Our results demonstrate phenological differences in arrival and departure timing among the goose species. Greater White-fronted Geese arrived earliest (October 16th to October 28th), followed by Swan Geese (October 9th to November 30th), with Bean Geese arriving latest (November 1st to November 17th). The average overwintering duration in Poyang Lake was approximately 149±8 days for Greater White-fronted Geese, 123±7 days for Bean Geese, and 128±26 days for Swan Geese. Analysis of migratory timing dynamics revealed relative stability and low interannual variation for Greater White-fronted and Bean Geese, while Swan Geese exhibited greater interannual variability. Spatially, protected areas remained the most important distribution areas for geese. However, increasing duration and home range expansion outside of protected areas were observed, particularly for Bean and Swan Geese. This study quantified the duration and spatial utilization of geese in sub-lakes, highlighting their ecological role in supporting migratory goose populations. It also identified important conservation areas for geese and determined protection gaps. We recommend expanding protected area boundaries to cover existing protection gaps and strengthening habitat management measures both inside and outside protected areas to ensure the long-term sustainability of these important wintering habitats. This research provides scientific support for identifying critical habitats and developing targeted conservation strategies for geese and their habitats.
Poyang Lake, China’s largest freshwater lake, serves as a crucial wintering ground for geese of East Asian. This study employed satellite tracking data from 2019 to 2024 to analyze the migratory phenology and spatial distribution patterns of Greater White-fronted Goose Anser albifrons, Swan Goose Anser cygnoides, and Bean Goose Anser fabalis. By integrating duration and home range data, we quantified the importance of Poyang Lake’s sub-lakes to these species. Our results demonstrate phenological differences in arrival and departure timing among the goose species. Greater White-fronted Geese arrived earliest (October 16th to October 28th), followed by Swan Geese (October 9th to November 30th), with Bean Geese arriving latest (November 1st to November 17th). The average overwintering duration in Poyang Lake was approximately 149±8 days for Greater White-fronted Geese, 123±7 days for Bean Geese, and 128±26 days for Swan Geese. Analysis of migratory timing dynamics revealed relative stability and low interannual variation for Greater White-fronted and Bean Geese, while Swan Geese exhibited greater interannual variability. Spatially, protected areas remained the most important distribution areas for geese. However, increasing duration and home range expansion outside of protected areas were observed, particularly for Bean and Swan Geese. This study quantified the duration and spatial utilization of geese in sub-lakes, highlighting their ecological role in supporting migratory goose populations. It also identified important conservation areas for geese and determined protection gaps. We recommend expanding protected area boundaries to cover existing protection gaps and strengthening habitat management measures both inside and outside protected areas to ensure the long-term sustainability of these important wintering habitats. This research provides scientific support for identifying critical habitats and developing targeted conservation strategies for geese and their habitats.
2026,(1):000-000, DOI: 10.18307/2026.0152
Available online: July 22, 2025
Abstract:
The Songzi River is one of the primary channels through which the Jingjiang River diverts water into Dongting Lake, and changes in its water diversion have significant implications for flood control in the river-lake system, water resource utilization, and water environmental ecology. Based on analysis of measured data and physical model experiments, this study investigates the relationships among water-sediment evolution, riverbed scouring, and diversion changes in the Yangtze main channel and Songzi Mouth reach following the operation of the Three Gorges Project.The results show that compared with the period from 1990 to 2002, the annual average sediment transport at Zhicheng Station decreased by approximately 90.6% during 2003–2022, with a synchronous reduction of about 87.1% in sediment diversion at Songzi Mouth. From 2003 to 2022, the bankfull channel between Zhicheng and Yangjiaonao experienced a total scouring volume of 239 million m3, with an average scouring depth of 2.3 m, leading to significant riverbed coarsening. In contrast, the bankfull channel at the Songzi Mouth reach was scoured by 43.25 million m3, with an average scouring depth of 3.0 m, forming a differential scouring rate compared to the pebble-sand mixed bed in the main channel.Physical model predictions indicate that long-term action of subsaturated flow will cause continuous downcutting of the sandy riverbed downstream of Yangjiaonao in the Yangtze main channel, leading to progressive declines in water levels at Yangjiaonao and corresponding reductions in diversion at Songzi Mouth. For a discharge of 7000 m3/s at Zhicheng Station, water levels at Yangjiaonao are projected to decrease by 1.58 m and 2.57 m in 2035 and 2050, respectively, resulting in diversion reductions of 8.3% and 16.7%. However, asymmetric scouring between the inner and outer parts of the mouth (with higher scouring rates in the sandy mouth reach, expanding the cross-sectional flow area) leads to increased diversion at Songzi Mouth by the end of 2035, even considering the water level decline at Yangjiaonao. During low-flow periods (with a discharge of 7000 m3/s at Zhicheng Station), diversion actually increases by 20.8%, with contribution rates of -33% from the Yangjiaonao water level drop and 133% from asymmetric mouth scouring. As the discharge increases, the absolute values of both contribution rates rise significantly, but their combined effect results in minimal net change in diversion volume, suggesting that these influences are primarily concentrated during medium- to low-flow periods.The differential riverbed composition regulates the scouring process and maintains stable diversion at Songzi Mouth. Increased low-flow diversion is beneficial for water resource allocation in Dongting Lake, but it may moderately lower main channel water levels and affect navigation during medium- to low-flow periods.
The Songzi River is one of the primary channels through which the Jingjiang River diverts water into Dongting Lake, and changes in its water diversion have significant implications for flood control in the river-lake system, water resource utilization, and water environmental ecology. Based on analysis of measured data and physical model experiments, this study investigates the relationships among water-sediment evolution, riverbed scouring, and diversion changes in the Yangtze main channel and Songzi Mouth reach following the operation of the Three Gorges Project.The results show that compared with the period from 1990 to 2002, the annual average sediment transport at Zhicheng Station decreased by approximately 90.6% during 2003–2022, with a synchronous reduction of about 87.1% in sediment diversion at Songzi Mouth. From 2003 to 2022, the bankfull channel between Zhicheng and Yangjiaonao experienced a total scouring volume of 239 million m3, with an average scouring depth of 2.3 m, leading to significant riverbed coarsening. In contrast, the bankfull channel at the Songzi Mouth reach was scoured by 43.25 million m3, with an average scouring depth of 3.0 m, forming a differential scouring rate compared to the pebble-sand mixed bed in the main channel.Physical model predictions indicate that long-term action of subsaturated flow will cause continuous downcutting of the sandy riverbed downstream of Yangjiaonao in the Yangtze main channel, leading to progressive declines in water levels at Yangjiaonao and corresponding reductions in diversion at Songzi Mouth. For a discharge of 7000 m3/s at Zhicheng Station, water levels at Yangjiaonao are projected to decrease by 1.58 m and 2.57 m in 2035 and 2050, respectively, resulting in diversion reductions of 8.3% and 16.7%. However, asymmetric scouring between the inner and outer parts of the mouth (with higher scouring rates in the sandy mouth reach, expanding the cross-sectional flow area) leads to increased diversion at Songzi Mouth by the end of 2035, even considering the water level decline at Yangjiaonao. During low-flow periods (with a discharge of 7000 m3/s at Zhicheng Station), diversion actually increases by 20.8%, with contribution rates of -33% from the Yangjiaonao water level drop and 133% from asymmetric mouth scouring. As the discharge increases, the absolute values of both contribution rates rise significantly, but their combined effect results in minimal net change in diversion volume, suggesting that these influences are primarily concentrated during medium- to low-flow periods.The differential riverbed composition regulates the scouring process and maintains stable diversion at Songzi Mouth. Increased low-flow diversion is beneficial for water resource allocation in Dongting Lake, but it may moderately lower main channel water levels and affect navigation during medium- to low-flow periods.
Available online: July 17, 2025
Abstract:
Surface water-heat-carbon fluxes are critical indicators reflecting the water-carbon cycles in lake ecosystems under changing climates, yet the impact of extreme environmental conditions such as drought on these processes remains to be further clarified. Poyang Lake is the largest freshwater lake in China and an internationally important wetland. It is not only a key node for the regulation of water resources in the Yangtze River Basin, but also plays an important role in the global carbon cycle and water cycle. In 2022, a rare consecutive meteorological drought event occurred in the Poyang Lake Basin during the summer and autumn seasons, and the most severe drought since 1949 hit the lake area. In this study, the multi-year monitoring data from the eddy covariance instrument at the Poyang Lake Wetland Observation and Research Station were adopted. The station is located on the beach of Poyang Lake (29°27" N, 116°03" E), and it has been continuously monitoring the variation processes of the water-heat-carbon fluxes in the lake since 2015. This study analyzed the variation patterns of water-heat-carbon fluxes and their response characteristics to the extreme drought event in Poyang Lake, in 2022. The results showed that: (1) On an annual scale, the latent heat flux was relatively high from July to September, with the peak value occurring in August, and the annual average value was 49.5 W/m2. The sensible heat flux was relatively high from September to November, with the peak value occurring in October, and the annual average value was 10.6 W/m2. The CO? flux exhibited obvious seasonal variations, and the carbon source and carbon sink shifted with hydrometeorological factors such as water level and net radiation. The annual CO? flux average value was 15.0 μmol·m?2·s?1. (2) On a daily scale, the sensible heat and latent heat fluxes were basically synchronous, showing a single peak at noon, while the CO? flux had a single peak at night. (3) The extreme drought event significantly intensified the carbon source effect of the wetland ecosystem by changing the energy allocation pattern. During the drought period, the latent heat flux, sensible heat flux, and CO? flux increased to 1.23 times, 1.78 times, and 5.44 times of the average values in the same historical period, respectively. (4) The correlation analysis showed that air temperature, wind speed, net radiation, precipitation, relative humidity, NDVI, and water level were the main factors affecting the water-heat-carbon fluxes. The stepwise regression analysis further revealed the influence mechanisms of various factors on the fluxes under different periods and underlying surface conditions. During the extreme drought period, when the underlying surface was water body, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: wind speed, air temperature > relative humidity > net radiation, water level. When the underlying surface was the beach, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: air temperature > wind speed, wind speed > NDVI, air temperature > VPD > precipitation. The extreme drought event mainly promoted the energy allocation to the sensible heat flux through the increase of air temperature, wind speed, and net radiation, and significantly stimulated the CO? release. This study revealed the response mechanisms of water-heat-carbon fluxes in lakes to extreme climate events and provided a scientific basis for predicting the responses of lake ecosystems under future climate change scenarios.
Surface water-heat-carbon fluxes are critical indicators reflecting the water-carbon cycles in lake ecosystems under changing climates, yet the impact of extreme environmental conditions such as drought on these processes remains to be further clarified. Poyang Lake is the largest freshwater lake in China and an internationally important wetland. It is not only a key node for the regulation of water resources in the Yangtze River Basin, but also plays an important role in the global carbon cycle and water cycle. In 2022, a rare consecutive meteorological drought event occurred in the Poyang Lake Basin during the summer and autumn seasons, and the most severe drought since 1949 hit the lake area. In this study, the multi-year monitoring data from the eddy covariance instrument at the Poyang Lake Wetland Observation and Research Station were adopted. The station is located on the beach of Poyang Lake (29°27" N, 116°03" E), and it has been continuously monitoring the variation processes of the water-heat-carbon fluxes in the lake since 2015. This study analyzed the variation patterns of water-heat-carbon fluxes and their response characteristics to the extreme drought event in Poyang Lake, in 2022. The results showed that: (1) On an annual scale, the latent heat flux was relatively high from July to September, with the peak value occurring in August, and the annual average value was 49.5 W/m2. The sensible heat flux was relatively high from September to November, with the peak value occurring in October, and the annual average value was 10.6 W/m2. The CO? flux exhibited obvious seasonal variations, and the carbon source and carbon sink shifted with hydrometeorological factors such as water level and net radiation. The annual CO? flux average value was 15.0 μmol·m?2·s?1. (2) On a daily scale, the sensible heat and latent heat fluxes were basically synchronous, showing a single peak at noon, while the CO? flux had a single peak at night. (3) The extreme drought event significantly intensified the carbon source effect of the wetland ecosystem by changing the energy allocation pattern. During the drought period, the latent heat flux, sensible heat flux, and CO? flux increased to 1.23 times, 1.78 times, and 5.44 times of the average values in the same historical period, respectively. (4) The correlation analysis showed that air temperature, wind speed, net radiation, precipitation, relative humidity, NDVI, and water level were the main factors affecting the water-heat-carbon fluxes. The stepwise regression analysis further revealed the influence mechanisms of various factors on the fluxes under different periods and underlying surface conditions. During the extreme drought period, when the underlying surface was water body, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: wind speed, air temperature > relative humidity > net radiation, water level. When the underlying surface was the beach, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: air temperature > wind speed, wind speed > NDVI, air temperature > VPD > precipitation. The extreme drought event mainly promoted the energy allocation to the sensible heat flux through the increase of air temperature, wind speed, and net radiation, and significantly stimulated the CO? release. This study revealed the response mechanisms of water-heat-carbon fluxes in lakes to extreme climate events and provided a scientific basis for predicting the responses of lake ecosystems under future climate change scenarios.
Available online: July 17, 2025
Abstract:
Water quality is a key factor in safeguarding ecosystem functions, protecting human health, and achieving sustainable development. Land use characteristics (including type, intensity, and landscape configuration) serve as important indicators of human activity and have significant impacts on river water quality, which vary across different spatial and temporal scales. This study focuses on the source region of the Chishui River and integrates two spatial scales: riparian buffer and sub-watershed. By applying variation partitioning analysis (VPA) and random forest modeling, we comprehensively quantify the independent and combined contributions of land use type, intensity, and landscape pattern to water quality, while identifying key influencing factors and their corresponding spatial scales. The results show that:① Landscape pattern is the dominant factor affecting water quality (explaining 33–58% of the variation), followed by land use type (11–22%) and intensity (4–16%);② Riparian landscape configuration exerts a more significant influence on water quality, while land use intensity at the sub-watershed scale provides stronger explanatory power;③ The proportion of built-up land, construction intensity (LUI_Con), and agricultural intensity (LUI_Cul) are key predictors of water quality, while forest cover and landscape connectivity play important roles in reducing TN and COD concentrations. These findings suggest that watershed water quality management should consider land use characteristics at multiple scales to identify optimal combinations of riparian and sub-watershed interventions. Specifically, we recommend prioritizing the control of industrial and domestic point-source pollution at the riparian scale, while enhancing agricultural non-point source management at the sub-watershed scale—thus forming an integrated "point-source and non-point source" control system. This study offers new empirical evidence on the multidimensional interactions and scale effects of land use–water quality relationships, providing important theoretical and practical insights for watershed resource protection and spatial planning optimization.
Water quality is a key factor in safeguarding ecosystem functions, protecting human health, and achieving sustainable development. Land use characteristics (including type, intensity, and landscape configuration) serve as important indicators of human activity and have significant impacts on river water quality, which vary across different spatial and temporal scales. This study focuses on the source region of the Chishui River and integrates two spatial scales: riparian buffer and sub-watershed. By applying variation partitioning analysis (VPA) and random forest modeling, we comprehensively quantify the independent and combined contributions of land use type, intensity, and landscape pattern to water quality, while identifying key influencing factors and their corresponding spatial scales. The results show that:① Landscape pattern is the dominant factor affecting water quality (explaining 33–58% of the variation), followed by land use type (11–22%) and intensity (4–16%);② Riparian landscape configuration exerts a more significant influence on water quality, while land use intensity at the sub-watershed scale provides stronger explanatory power;③ The proportion of built-up land, construction intensity (LUI_Con), and agricultural intensity (LUI_Cul) are key predictors of water quality, while forest cover and landscape connectivity play important roles in reducing TN and COD concentrations. These findings suggest that watershed water quality management should consider land use characteristics at multiple scales to identify optimal combinations of riparian and sub-watershed interventions. Specifically, we recommend prioritizing the control of industrial and domestic point-source pollution at the riparian scale, while enhancing agricultural non-point source management at the sub-watershed scale—thus forming an integrated "point-source and non-point source" control system. This study offers new empirical evidence on the multidimensional interactions and scale effects of land use–water quality relationships, providing important theoretical and practical insights for watershed resource protection and spatial planning optimization.
Available online: July 17, 2025
Abstract:
The sediment peak regulation (SPR) in the Three Gorges Reservoir (TGR) during flood season can significantly improve the sediment discharge effect. Studying the control indicators of SPR is of great importance for ensuring the safety of reservoir storage capacity and improving the comprehensive benefits of reservoir. On the basis of data recorded at hydrological stations in the TGR between 2003 and 2023, the characteristics of sediment transport during flood season in the reservoir were identified. After the impoundment of cascade reservoirs in the lower reaches of Jinsha River, the start-up control and process regulation indicators of the SPR in the TGR were discussed. The results indicate that the amount of sediment entering the TGR was greatly reduced since the cascade reservoirs in the lower reaches of Jinsha River were impounded. Sediment transport in the TGR occurred mainly during flood events. The main consideration is to start the SPR for the floods with forecasted peak discharge at Cuntan station not less than 50,000 m3/s or forecasted peak sediment concentration at Cuntan station not less than 1.5 kg/m3, and forecasted 7-day average sediment concentration at Cuntan station not less than 0.5kg/m3. With flood control safety as the premise, and taking into account the multi-objective benefit of the reservoir and the measured flow and sediment conditions during the SPR, dynamic scheduling can be implemented according to the dispatching strategies of the three periods: water discharge peak blocking, sediment transport in the reservoir, and sediment discharge in front of the dam. In addition, real-time monitoring and forecasting of sediment during flood season is the basis of SPR. It is necessary to continuously optimize the sediment monitoring and forecasting technologies, so as to accurately control the start time and regulation process of SPR, and improve the comprehensive benefits of the TGR. This study can provide technical support for the optimization and refinement of SPR in the TGR during flood season.
The sediment peak regulation (SPR) in the Three Gorges Reservoir (TGR) during flood season can significantly improve the sediment discharge effect. Studying the control indicators of SPR is of great importance for ensuring the safety of reservoir storage capacity and improving the comprehensive benefits of reservoir. On the basis of data recorded at hydrological stations in the TGR between 2003 and 2023, the characteristics of sediment transport during flood season in the reservoir were identified. After the impoundment of cascade reservoirs in the lower reaches of Jinsha River, the start-up control and process regulation indicators of the SPR in the TGR were discussed. The results indicate that the amount of sediment entering the TGR was greatly reduced since the cascade reservoirs in the lower reaches of Jinsha River were impounded. Sediment transport in the TGR occurred mainly during flood events. The main consideration is to start the SPR for the floods with forecasted peak discharge at Cuntan station not less than 50,000 m3/s or forecasted peak sediment concentration at Cuntan station not less than 1.5 kg/m3, and forecasted 7-day average sediment concentration at Cuntan station not less than 0.5kg/m3. With flood control safety as the premise, and taking into account the multi-objective benefit of the reservoir and the measured flow and sediment conditions during the SPR, dynamic scheduling can be implemented according to the dispatching strategies of the three periods: water discharge peak blocking, sediment transport in the reservoir, and sediment discharge in front of the dam. In addition, real-time monitoring and forecasting of sediment during flood season is the basis of SPR. It is necessary to continuously optimize the sediment monitoring and forecasting technologies, so as to accurately control the start time and regulation process of SPR, and improve the comprehensive benefits of the TGR. This study can provide technical support for the optimization and refinement of SPR in the TGR during flood season.
Available online: July 15, 2025
Abstract:
There is a very high risk of odorous compounds contaminating drinking water sources in the Changjiang River catchment in spring. However, the key drivers for the occurrence of odorous compounds are still unclear. In May 2024, nine drinking water source reservoirs across the upper, middle and lower reaches of the Changjiang River were investigated. Four odorous compounds, 2-methylisoborneol (2-MIB), geosmin (GSM), β-cyclocitral (CYC) and β-ionone (ION) and their associated environmental factors were surveyed. The results showed that 2-MIB was the most common odorous compound in research region, with an average concentration of 35.5 ng/L across the 32 samples from 9 reservoirs (59.4% exceeding the detection threshold of 10.0 ng/L). GSM posed a lower risk, with an average concentration of 2.9 ng/L and only 12.5% exceeding the threshold value of 10 ng/L. CYC (averaged at 18.2 ng/L) and ION (averaged at 7.2 ng/L) exhibited minimal odorous concerns. Pseudanabaena sp. was identified as a likely major producer of 2-MIB, with its cell density showing a significant positive correlation with the concentration of 2-MIB. However, the presence of 2-MIB in two reservoirs without detectable Pseudanabaena, indicated more complex 2-MIB sources in some reservoirs. 2-MIB levels positively correlated with the trophic state index, demonstrating that eutrophication directly promotes 2-MIB production. The 7-days accumulated rainfall amount ahead sampling was negative relative to the 2-MIB concentration, suggested that short-term heavy rainfall processes will strongly change the odor compounds risk in reservoirs. Despite most drinking water source reservoirs in this region were under mesotrophic conditions, while it shows widespread 2-MIB exceedances. It is vital to reduce external nutrient loads and optimize aquatic food webs to prevent odorous issues and ensure drinking safety.
There is a very high risk of odorous compounds contaminating drinking water sources in the Changjiang River catchment in spring. However, the key drivers for the occurrence of odorous compounds are still unclear. In May 2024, nine drinking water source reservoirs across the upper, middle and lower reaches of the Changjiang River were investigated. Four odorous compounds, 2-methylisoborneol (2-MIB), geosmin (GSM), β-cyclocitral (CYC) and β-ionone (ION) and their associated environmental factors were surveyed. The results showed that 2-MIB was the most common odorous compound in research region, with an average concentration of 35.5 ng/L across the 32 samples from 9 reservoirs (59.4% exceeding the detection threshold of 10.0 ng/L). GSM posed a lower risk, with an average concentration of 2.9 ng/L and only 12.5% exceeding the threshold value of 10 ng/L. CYC (averaged at 18.2 ng/L) and ION (averaged at 7.2 ng/L) exhibited minimal odorous concerns. Pseudanabaena sp. was identified as a likely major producer of 2-MIB, with its cell density showing a significant positive correlation with the concentration of 2-MIB. However, the presence of 2-MIB in two reservoirs without detectable Pseudanabaena, indicated more complex 2-MIB sources in some reservoirs. 2-MIB levels positively correlated with the trophic state index, demonstrating that eutrophication directly promotes 2-MIB production. The 7-days accumulated rainfall amount ahead sampling was negative relative to the 2-MIB concentration, suggested that short-term heavy rainfall processes will strongly change the odor compounds risk in reservoirs. Despite most drinking water source reservoirs in this region were under mesotrophic conditions, while it shows widespread 2-MIB exceedances. It is vital to reduce external nutrient loads and optimize aquatic food webs to prevent odorous issues and ensure drinking safety.
kongjie, zhouzhongfa, wangyanbi, lirui, lili, zhangxinyue, dingcaixia, xierukai, sunyaopeng, caoweitang
Available online: July 15, 2025
Abstract:
The influx of a large amount of sulfate (SO42-) into water bodies can deteriorate the water environment quality. During the period from 2019 to 2023, water samples from the Pingzhai Reservoir Basin in the southwestern karst area, precipitation samples, and sewage samples were collected. The physical and chemical indicators of the water bodies, as well as the characteristics of sulfate sulfur and oxygen isotopes (δ34SSO4, δ18OSO4), hydrogen and oxygen isotopes of water (δDH2O, δ18OH2O), and dissolved inorganic carbon isotopes (δ13CDIC) were analyzed during the monitoring period. Qualitative and quantitative studies on the sources of SO42- in the water bodies were carried out. The hydrochemical types of the basin are mainly of the Ca-HCO3 type and Ca-HCO3-SO4 type, and the hydrochemical characteristics are influenced by the dissolution of carbonate rocks. Isotope characteristics reveal that the biogeochemical process of SO42- in the Pingzhai Reservoir Basin is dominated by oxidation (when sulfides are oxidized, on average, 61% of the oxygen comes from the surrounding water bodies). During the monitoring period, the sources of SO42- in the basin are mainly sulfide oxidation, soil organic sulfur, and agricultural sulfur fertilizers. The results of quantitative calculations show that sulfide oxidation has the highest average contribution rate (72.9%), followed by soil organic sulfur (14.1%) and agricultural sulfur fertilizers (12.9%). The results of uncertainty analysis indicate that the contribution rate of agricultural sulfur fertilizers is the most stable, while that of sulfide oxidation shows relatively large uncertainty. The research results can provide data reference and scientific basis for the protection of water environment quality in the Pingzhai Reservoir and similar karst areas.
The influx of a large amount of sulfate (SO42-) into water bodies can deteriorate the water environment quality. During the period from 2019 to 2023, water samples from the Pingzhai Reservoir Basin in the southwestern karst area, precipitation samples, and sewage samples were collected. The physical and chemical indicators of the water bodies, as well as the characteristics of sulfate sulfur and oxygen isotopes (δ34SSO4, δ18OSO4), hydrogen and oxygen isotopes of water (δDH2O, δ18OH2O), and dissolved inorganic carbon isotopes (δ13CDIC) were analyzed during the monitoring period. Qualitative and quantitative studies on the sources of SO42- in the water bodies were carried out. The hydrochemical types of the basin are mainly of the Ca-HCO3 type and Ca-HCO3-SO4 type, and the hydrochemical characteristics are influenced by the dissolution of carbonate rocks. Isotope characteristics reveal that the biogeochemical process of SO42- in the Pingzhai Reservoir Basin is dominated by oxidation (when sulfides are oxidized, on average, 61% of the oxygen comes from the surrounding water bodies). During the monitoring period, the sources of SO42- in the basin are mainly sulfide oxidation, soil organic sulfur, and agricultural sulfur fertilizers. The results of quantitative calculations show that sulfide oxidation has the highest average contribution rate (72.9%), followed by soil organic sulfur (14.1%) and agricultural sulfur fertilizers (12.9%). The results of uncertainty analysis indicate that the contribution rate of agricultural sulfur fertilizers is the most stable, while that of sulfide oxidation shows relatively large uncertainty. The research results can provide data reference and scientific basis for the protection of water environment quality in the Pingzhai Reservoir and similar karst areas.
Available online: July 09, 2025
Abstract:
The sediment seed bank"s ability to efficiently connect previous vegetation"s genetic memory with future vegetation"s development trend is crucial for maintaining community species diversity, restoring ecosystems, and promoting the natural regeneration of aquatic vegetation in shallow lakes. The submerged plant survey and seed bank germination experiments were used in this study to analyze the spatial distribution characteristics of the submerged plant seed bank of Caohai Lake in Guizhou. A comprehensive restoration potential evaluation model was built based on the submerged vegetation, sediment seed bank, sediment, and water quality characteristics to evaluate the restoration potential of various lake areas. Results showed that: (1) the seed bank"s density ranged from 976 to 23,537 seeds/m2, which was comparatively well preserved; it contained nine species from five families, seven genus. The dominant families were the Potamogetonaceae, Hydrocharitaceae, and Najadaceae. The dominant species was Charophyte, which had the highest seed bank density (mean 6057 seeds/m2), which was noticeably higher than others. (2) The sediment seed bank in the Caohai Lake demonstrated obvious spatial heterogeneity, with higher density in the southern and northeast inshore areas and lower density in the mid-lake area. The seed bank was primarily distributed in the surface sediment (0–15 cm), indicating an obvious "surface aggregation" phenomenon. The discrete coefficient analysis revealed that Charophyte, Vallisneria natans, and Potamogenton perfoliatus L had aggregated distribution patterns, while the remaining species had uniform distribution patterns. Furthermore, Sorensen"s similarity coefficient analysis suggested that the succession of submerged communities in Caohai Lake may be quite stable. (3) The southwest and northeast of the Caohai near-shore lake area have high recovery potential for submerged and are designated as "priority recovery areas" The recovery strategy entails keeping water levels low throughout the critical period of submerged seed germination and utilizing the seed bank to achieve natural submerged recovery. The near-shore areas in the northwest and north have a low potential for restoration due to the deeper water level and low seed bank density and are considered“transition zones". The restoration strategy is gradually restoring submerged Caohai Lake by manually adding seeds or planting seedlings under low-water operations. The outlet, southeast side, and center of the lake are considered the“key restoration areas” due to their lowest restoration potential. Because of the serious nutrient loading and the high density of the seed bank, the restoration strategy is to control endogenous pollution and improve water quality, create suitable habitats, and use the seed bank to realize the near-natural restoration of submerged plants. This study can provide a theoretical basis and support for recovering aquatic plant ecosystems in shallow lakes undergoing degradation.
The sediment seed bank"s ability to efficiently connect previous vegetation"s genetic memory with future vegetation"s development trend is crucial for maintaining community species diversity, restoring ecosystems, and promoting the natural regeneration of aquatic vegetation in shallow lakes. The submerged plant survey and seed bank germination experiments were used in this study to analyze the spatial distribution characteristics of the submerged plant seed bank of Caohai Lake in Guizhou. A comprehensive restoration potential evaluation model was built based on the submerged vegetation, sediment seed bank, sediment, and water quality characteristics to evaluate the restoration potential of various lake areas. Results showed that: (1) the seed bank"s density ranged from 976 to 23,537 seeds/m2, which was comparatively well preserved; it contained nine species from five families, seven genus. The dominant families were the Potamogetonaceae, Hydrocharitaceae, and Najadaceae. The dominant species was Charophyte, which had the highest seed bank density (mean 6057 seeds/m2), which was noticeably higher than others. (2) The sediment seed bank in the Caohai Lake demonstrated obvious spatial heterogeneity, with higher density in the southern and northeast inshore areas and lower density in the mid-lake area. The seed bank was primarily distributed in the surface sediment (0–15 cm), indicating an obvious "surface aggregation" phenomenon. The discrete coefficient analysis revealed that Charophyte, Vallisneria natans, and Potamogenton perfoliatus L had aggregated distribution patterns, while the remaining species had uniform distribution patterns. Furthermore, Sorensen"s similarity coefficient analysis suggested that the succession of submerged communities in Caohai Lake may be quite stable. (3) The southwest and northeast of the Caohai near-shore lake area have high recovery potential for submerged and are designated as "priority recovery areas" The recovery strategy entails keeping water levels low throughout the critical period of submerged seed germination and utilizing the seed bank to achieve natural submerged recovery. The near-shore areas in the northwest and north have a low potential for restoration due to the deeper water level and low seed bank density and are considered“transition zones". The restoration strategy is gradually restoring submerged Caohai Lake by manually adding seeds or planting seedlings under low-water operations. The outlet, southeast side, and center of the lake are considered the“key restoration areas” due to their lowest restoration potential. Because of the serious nutrient loading and the high density of the seed bank, the restoration strategy is to control endogenous pollution and improve water quality, create suitable habitats, and use the seed bank to realize the near-natural restoration of submerged plants. This study can provide a theoretical basis and support for recovering aquatic plant ecosystems in shallow lakes undergoing degradation.
Available online: July 03, 2025
Abstract:
In order to quantitatively evaluate the impact of human activities on the changes of hydrologic drought characteristics in Poyang Lake Basin, This article analyzes the inter-annual variation trend of precipitation, temperature, evaporation and runoff from 1959 to 2022 according to the data of meteorological and hydrologic stations in the basin. The relationship curve between cumulative annual precipitation and runoff in the five watershed divisions of Poyang Lake is drawn by using the double cumulative curve method, based on which and combined with the mutation point test,the reference period and change period affected by human activities are divided. According to the measured data of precipitation, evaporation and runoff for each period, the parameters of the two - parameter monthly water balance model are calibrated, and the simulation results are tested using Nash efficiency coefficient, correlation coefficient, and water balance error. By simulating the reduction and reconstruction of monthly runoff during the reference and change periods, and the impact of climate change and human activities on runoff is obtained; Using the SRI as the hydrological drought index, drought events during the change period were identified through run length theory. The characteristics of annual average cumulative drought intensity, the maximum severity of a single drought, and drought frequency before and after parameter reduction were compared. The results show that human activities have generally reduced the runoff depth in the basin, with more significant impacts on the dry season. Spatially, the impacts on the Fu River and Rao River basins are the most obvious, with the annual average runoff depth and the runoff depth during the dry season decreasing by 8.5%, 9.2%, 12.0%, and 12.3% respectively. The frequency and severity of hydrological droughts in the Poyang Lake Basin during the change period have generally increased. The average annual number of droughts, the average annual drought severity, and the maximum severity of a single drought have increased by approximately 21.3%, 55.4%, and 24.3% respectively compared with the reference period. The research can provide a reference for the long-term prediction of the drought trend in the Poyang Lake Basin.
In order to quantitatively evaluate the impact of human activities on the changes of hydrologic drought characteristics in Poyang Lake Basin, This article analyzes the inter-annual variation trend of precipitation, temperature, evaporation and runoff from 1959 to 2022 according to the data of meteorological and hydrologic stations in the basin. The relationship curve between cumulative annual precipitation and runoff in the five watershed divisions of Poyang Lake is drawn by using the double cumulative curve method, based on which and combined with the mutation point test,the reference period and change period affected by human activities are divided. According to the measured data of precipitation, evaporation and runoff for each period, the parameters of the two - parameter monthly water balance model are calibrated, and the simulation results are tested using Nash efficiency coefficient, correlation coefficient, and water balance error. By simulating the reduction and reconstruction of monthly runoff during the reference and change periods, and the impact of climate change and human activities on runoff is obtained; Using the SRI as the hydrological drought index, drought events during the change period were identified through run length theory. The characteristics of annual average cumulative drought intensity, the maximum severity of a single drought, and drought frequency before and after parameter reduction were compared. The results show that human activities have generally reduced the runoff depth in the basin, with more significant impacts on the dry season. Spatially, the impacts on the Fu River and Rao River basins are the most obvious, with the annual average runoff depth and the runoff depth during the dry season decreasing by 8.5%, 9.2%, 12.0%, and 12.3% respectively. The frequency and severity of hydrological droughts in the Poyang Lake Basin during the change period have generally increased. The average annual number of droughts, the average annual drought severity, and the maximum severity of a single drought have increased by approximately 21.3%, 55.4%, and 24.3% respectively compared with the reference period. The research can provide a reference for the long-term prediction of the drought trend in the Poyang Lake Basin.
Available online: July 02, 2025
Abstract:
Rivers are links connecting the biogeochemical processes among terrestrial, oceanic, and atmospheric carbon pools, and are important participants in the global water and carbon cycles. Riverine partial pressure of carbon dioxide (pCO2) is a key indicator reflecting the CO2 exchange process at the riverine water-air interface, which exhibits complex spatiotemporal variations due to the co-impacts of various natural and anthropogenic factors. However, the current understanding of the main controlling factors and their effects on riverine pCO2 is still very limited. In this study, the spatiotemporal distribution characteristics of riverine pCO2 were identified, and the relative contributions and controlling effects of the potential controlling factors were quantified and revealed using an interpretable machine learning method (boost regression tree (BRT) and accumulated local effects (ALE)), based on monthly datasets with high spatial resolution in the Han River Basin (HRB). Results indicated that multi-year average riverine pCO2 in the HRB showed an increasing trend from upstream to downstream, and was higher than the atmospheric average. The fluctuation type of multi-year monthly average riverine pCO2 in the HRB could be classified into three types based on the k-Shape clustering algorithm, with stationary (T1), unimodal (T2), and bimodal (T3) structures, respectively. The BRT model effectively simulated the multi-year average and multi-year monthly average values of riverine pCO2 in the HRB, showing high performances (r > 0.86, NSE > 0.75) and acceptable errors (MAE < 212.18 μatm, RMSE < 274.16 μatm) in replicate experiments. Multi-year average riverine pCO2 was mainly controlled by temperature factors, with a total relative contribution rate of about 66.1%. Relative contributions of controlling factors for multi-year monthly average riverine pCO2 varied greatly among each fluctuation type, while temperature factors still played a critical role (approximately 26.6% ~ 46.9%). Vegetation and water quantity factors had high contributions in type T2 and T3, respectively, while the importance of water quality factors was relatively limited (less than about 20.1%). The nonlinear and non-monotonic relationships between riverine pCO2 and its potential controlling factors were revealed based on ALE analysis results, and showed significant differences between multi-year average and multi-year monthly average scales, as well as between different fluctuation types. This study revealed the complex spatiotemporal variations of the main controlling factors and their effects on riverine pCO2 in the HRB, improving the understanding of riverine carbon cycle process.
Rivers are links connecting the biogeochemical processes among terrestrial, oceanic, and atmospheric carbon pools, and are important participants in the global water and carbon cycles. Riverine partial pressure of carbon dioxide (pCO2) is a key indicator reflecting the CO2 exchange process at the riverine water-air interface, which exhibits complex spatiotemporal variations due to the co-impacts of various natural and anthropogenic factors. However, the current understanding of the main controlling factors and their effects on riverine pCO2 is still very limited. In this study, the spatiotemporal distribution characteristics of riverine pCO2 were identified, and the relative contributions and controlling effects of the potential controlling factors were quantified and revealed using an interpretable machine learning method (boost regression tree (BRT) and accumulated local effects (ALE)), based on monthly datasets with high spatial resolution in the Han River Basin (HRB). Results indicated that multi-year average riverine pCO2 in the HRB showed an increasing trend from upstream to downstream, and was higher than the atmospheric average. The fluctuation type of multi-year monthly average riverine pCO2 in the HRB could be classified into three types based on the k-Shape clustering algorithm, with stationary (T1), unimodal (T2), and bimodal (T3) structures, respectively. The BRT model effectively simulated the multi-year average and multi-year monthly average values of riverine pCO2 in the HRB, showing high performances (r > 0.86, NSE > 0.75) and acceptable errors (MAE < 212.18 μatm, RMSE < 274.16 μatm) in replicate experiments. Multi-year average riverine pCO2 was mainly controlled by temperature factors, with a total relative contribution rate of about 66.1%. Relative contributions of controlling factors for multi-year monthly average riverine pCO2 varied greatly among each fluctuation type, while temperature factors still played a critical role (approximately 26.6% ~ 46.9%). Vegetation and water quantity factors had high contributions in type T2 and T3, respectively, while the importance of water quality factors was relatively limited (less than about 20.1%). The nonlinear and non-monotonic relationships between riverine pCO2 and its potential controlling factors were revealed based on ALE analysis results, and showed significant differences between multi-year average and multi-year monthly average scales, as well as between different fluctuation types. This study revealed the complex spatiotemporal variations of the main controlling factors and their effects on riverine pCO2 in the HRB, improving the understanding of riverine carbon cycle process.
Available online: July 01, 2025
Abstract:
As one of the largest developing countries in the world, China is facing an increasingly severe pollution problem with PAEs (phthalates). PAEs, as plasticizers, are widely used in industries, food industry, and pharmaceutical industry. Due to their large usage and lack of standardized treatment, they have accumulated in the environment over the long term, showing significant toxicity. To explore the occurrence characteristics of PAEs in typical Chinese lakes and the effects of human activities, this study systematically analyzed the multi-media occurrence, spatial distribution, ecological risks, and potential sources of PAEs in the water bodies and sediments of 30 typical lakes in China. The results indicate that the concentration range of PAEs in the aqueous and sediment phases is 0.01~27.60 μg/L and 28.8~74935 ng/g, respectively, with di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) being the main PAEs in both phases; the spatial distribution of the lake areas shows significant differences, with the most severe pollution occurring in the middle and lower reaches of the Yangtze River. Among them, di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the main components of PAEs in lake water and sediments, with the highest contribution rates. The spatial distribution of the lake areas shows significant differences, with the lakes in the middle and lower reaches of the Yangtze River being the most severely polluted. Based on the ecological risk assessment using risk quotients (RQ), it was found that about 30% of the lakes pose a high risk to crustaceans, with DEHP and DBP being the main PAEs components posing high risks. Further principal component analysis and multiple linear regression showed that industrial wastewater discharge and agricultural production activities are the main sources of PAEs pollution, especially with a significant positive correlation (p < 0.05) between the use of agricultural films, pesticide usage, and the concentrations of DEHP and DBP. The study results indicate that PAEs have significant multi-media distribution characteristics in the lake water-sediment system and are profoundly influenced by human activities. Therefore, it is recommended to strengthen the management of PAEs additives in agricultural production and improve the removal efficiency of PAEs in industrial wastewater treatment processes to reduce the pollution load of lake water bodies. This study reveals the environmental behavior, risk characteristics, and anthropogenic driving mechanisms of PAEs in typical Chinese lakes, providing a scientific basis for the formulation of water ecological and environmental protection strategies.
As one of the largest developing countries in the world, China is facing an increasingly severe pollution problem with PAEs (phthalates). PAEs, as plasticizers, are widely used in industries, food industry, and pharmaceutical industry. Due to their large usage and lack of standardized treatment, they have accumulated in the environment over the long term, showing significant toxicity. To explore the occurrence characteristics of PAEs in typical Chinese lakes and the effects of human activities, this study systematically analyzed the multi-media occurrence, spatial distribution, ecological risks, and potential sources of PAEs in the water bodies and sediments of 30 typical lakes in China. The results indicate that the concentration range of PAEs in the aqueous and sediment phases is 0.01~27.60 μg/L and 28.8~74935 ng/g, respectively, with di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) being the main PAEs in both phases; the spatial distribution of the lake areas shows significant differences, with the most severe pollution occurring in the middle and lower reaches of the Yangtze River. Among them, di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the main components of PAEs in lake water and sediments, with the highest contribution rates. The spatial distribution of the lake areas shows significant differences, with the lakes in the middle and lower reaches of the Yangtze River being the most severely polluted. Based on the ecological risk assessment using risk quotients (RQ), it was found that about 30% of the lakes pose a high risk to crustaceans, with DEHP and DBP being the main PAEs components posing high risks. Further principal component analysis and multiple linear regression showed that industrial wastewater discharge and agricultural production activities are the main sources of PAEs pollution, especially with a significant positive correlation (p < 0.05) between the use of agricultural films, pesticide usage, and the concentrations of DEHP and DBP. The study results indicate that PAEs have significant multi-media distribution characteristics in the lake water-sediment system and are profoundly influenced by human activities. Therefore, it is recommended to strengthen the management of PAEs additives in agricultural production and improve the removal efficiency of PAEs in industrial wastewater treatment processes to reduce the pollution load of lake water bodies. This study reveals the environmental behavior, risk characteristics, and anthropogenic driving mechanisms of PAEs in typical Chinese lakes, providing a scientific basis for the formulation of water ecological and environmental protection strategies.
Available online: June 27, 2025
Abstract:
Abstract: In recent years, excessive input and inefficient utilization of nitrogen and phosphorus in the cropping system of the Poyang Lake Basin have led to significant losses of these elements, resulting in persistent exceedances of nitrogen and phosphorus standards, as well as other environmental issues. Therefore, quantitatively tracing the spatiotemporal patterns of nitrogen and phosphorus metabolism in the cropping system of Poyang Lake Basin is crucial for ensuring the sustainability of the basin"s ecosystem. This study applied the Material Flow Analysis (MFA) method to investigate the spatiotemporal variations of nitrogen and phosphorus fluxes in cropping systems across the Poyang Lake Basin from 2000 to 2022.Four scenarios were designed based on the current status of nitrogen and phosphorus pollutant emissions: a baseline scenario, a scenario with reduced fertilizer inputs to arable land, a scenario with increased straw recycling rates, and a scenario with comprehensive measures. The emission reduction potentials was quantitatively calculated under various scenarios and finally the optimal strategies for nitrogen and phosphorus pollutant emission reduction and prevention were proposed. The results show that the nitrogen and phosphorus inputs in the basin initially increased, then fluctuated stably, peaking around 2015. Spatially, the total nitrogen and phosphorus inputs are highest in the coastal lake district, reaching 281,000 tons of nitrogen and 64,000 tons of phosphorus, respectively, with chemical and organic fertilizers accounting for over half of the total inputs. In terms of the nutrient use efficiency, the combined use rate of nitrogen and phosphorus were 48.5% and 31.0% respectively. The nitrogen and phosphorus utilization rates for all crops has declined since 2010, and the nutrient input nitrogen and phosphorus ratio has also decreased continuously, with an average N/P of 3.9. Scenario analysis suggests that implementing measures to reduce chemical fertilizer use could decrease nitrogen output by 150,000 tonnes by 2050, nitrogen and phosphorus emissions can be reduced by 159,000 tons, reducing pollutants by 53.4%. compared with the baseline scenario, the ratio of N/P discharged into the environment can rise to 6.5. Reducing fertilizer application accounts for 75.7% of the emission reduction, demonstrating its effectiveness as a mitigation strategy. By quantitatively analyzing the nitrogen and phosphorus structure of cropping system and tracing the nitrogen and phosphorus inputs over the past 20 years in Poyang Lake Basin, identifying and judging the change trend of the nitrogen and phosphorus ratio, This analysis allows us to systematically evaluate the key processes of the agricultural system and provides a scientific basis for developing effective integrated nitrogen and phosphorus management measures in the Poyang Lake Basin by evaluating the potential outcomes of future scenarios.
Abstract: In recent years, excessive input and inefficient utilization of nitrogen and phosphorus in the cropping system of the Poyang Lake Basin have led to significant losses of these elements, resulting in persistent exceedances of nitrogen and phosphorus standards, as well as other environmental issues. Therefore, quantitatively tracing the spatiotemporal patterns of nitrogen and phosphorus metabolism in the cropping system of Poyang Lake Basin is crucial for ensuring the sustainability of the basin"s ecosystem. This study applied the Material Flow Analysis (MFA) method to investigate the spatiotemporal variations of nitrogen and phosphorus fluxes in cropping systems across the Poyang Lake Basin from 2000 to 2022.Four scenarios were designed based on the current status of nitrogen and phosphorus pollutant emissions: a baseline scenario, a scenario with reduced fertilizer inputs to arable land, a scenario with increased straw recycling rates, and a scenario with comprehensive measures. The emission reduction potentials was quantitatively calculated under various scenarios and finally the optimal strategies for nitrogen and phosphorus pollutant emission reduction and prevention were proposed. The results show that the nitrogen and phosphorus inputs in the basin initially increased, then fluctuated stably, peaking around 2015. Spatially, the total nitrogen and phosphorus inputs are highest in the coastal lake district, reaching 281,000 tons of nitrogen and 64,000 tons of phosphorus, respectively, with chemical and organic fertilizers accounting for over half of the total inputs. In terms of the nutrient use efficiency, the combined use rate of nitrogen and phosphorus were 48.5% and 31.0% respectively. The nitrogen and phosphorus utilization rates for all crops has declined since 2010, and the nutrient input nitrogen and phosphorus ratio has also decreased continuously, with an average N/P of 3.9. Scenario analysis suggests that implementing measures to reduce chemical fertilizer use could decrease nitrogen output by 150,000 tonnes by 2050, nitrogen and phosphorus emissions can be reduced by 159,000 tons, reducing pollutants by 53.4%. compared with the baseline scenario, the ratio of N/P discharged into the environment can rise to 6.5. Reducing fertilizer application accounts for 75.7% of the emission reduction, demonstrating its effectiveness as a mitigation strategy. By quantitatively analyzing the nitrogen and phosphorus structure of cropping system and tracing the nitrogen and phosphorus inputs over the past 20 years in Poyang Lake Basin, identifying and judging the change trend of the nitrogen and phosphorus ratio, This analysis allows us to systematically evaluate the key processes of the agricultural system and provides a scientific basis for developing effective integrated nitrogen and phosphorus management measures in the Poyang Lake Basin by evaluating the potential outcomes of future scenarios.
Yue Lintan, Yang Yifan, Zhuang Xinfeng, Chen Weiyu, Kong Xiangzhen, Deng Jianming, Zhao Zhonghua, Lu Yingcheng, Zhu Guangwei, Qin Boqiang
Available online: June 25, 2025
Abstract:
The intensification of global warming has led to a significant increase in the frequency and intensity of heatwave events. Exploring their impact on ecological processes such as lake nutrient salts, chlorophyll-a (Chla), and phytoplankton growth is crucial for understanding the ecological response and feedback mechanisms of lakes under heatwave conditions and providing scientific support for lake management and regulation under climate change. This study, based on the GOTM-WET model, simulated the impact of the 2022 summer heatwave on Chla concentration in North Taihu Lake, with a focus on analyzing the effects of different heatwave intensities on Chla and their possible mechanisms. The results indicated that the 2022 summer heatwave significantly suppressed Chla concentration, and the inhibitory effect intensified with the increase in heatwave intensity. Further analysis revealed that the maximum water temperature during the 2022 heatwave exceeded 37°C, possibly surpassing the optimal growth temperature for most algae, thereby inhibiting their growth. Additionally, the heatwave intensified water column stratification, leading to a reduction in total nitrogen (TN) and total phosphorus (TP) concentrations in the surface layer and their accumulation in the bottom layer. This vertical differentiation of nutrients limited the nutrient supply required for surface algae growth, further suppressing the increase in Chla concentration. This study revealed the potential impact mechanisms of dual factors of water temperature and nutrients on lake algae growth under extreme high-temperature conditions, deepening the understanding of the effects of heatwave events on lake ecosystem processes.
The intensification of global warming has led to a significant increase in the frequency and intensity of heatwave events. Exploring their impact on ecological processes such as lake nutrient salts, chlorophyll-a (Chla), and phytoplankton growth is crucial for understanding the ecological response and feedback mechanisms of lakes under heatwave conditions and providing scientific support for lake management and regulation under climate change. This study, based on the GOTM-WET model, simulated the impact of the 2022 summer heatwave on Chla concentration in North Taihu Lake, with a focus on analyzing the effects of different heatwave intensities on Chla and their possible mechanisms. The results indicated that the 2022 summer heatwave significantly suppressed Chla concentration, and the inhibitory effect intensified with the increase in heatwave intensity. Further analysis revealed that the maximum water temperature during the 2022 heatwave exceeded 37°C, possibly surpassing the optimal growth temperature for most algae, thereby inhibiting their growth. Additionally, the heatwave intensified water column stratification, leading to a reduction in total nitrogen (TN) and total phosphorus (TP) concentrations in the surface layer and their accumulation in the bottom layer. This vertical differentiation of nutrients limited the nutrient supply required for surface algae growth, further suppressing the increase in Chla concentration. This study revealed the potential impact mechanisms of dual factors of water temperature and nutrients on lake algae growth under extreme high-temperature conditions, deepening the understanding of the effects of heatwave events on lake ecosystem processes.
Available online: June 23, 2025
Abstract:
Dongting Lake is an important lake in the middle reach of the Yangtze River, and accurately modelling the runoff corresponding relationships of its various input and output stations is crucial for regional ecological protection and flood control and drought defense. To address the complex runoff response relationships in the Dongting Lake basin, this study proposes a multiple-input and multiple-output runoff response model based on graph neural networks. Firstly, the model utilizes the basin topological spatial structure of the Yangtze River, Dongting Lake and Sishui to transform the original observation sequences at each station into graph-structured data to characterize the spatial characteristics of the basin. Secondly, through the mutual correlation analysis method, the time lag relationship between the observed variables at each station is identified to determine the input feature step of the model. Finally, graph neural networks are employed to aggregate and update the features to capture the complex spatial and temporal dependencies among the control station, and to realize the runoff simulation at multiple stations. The results show that in the flood event, compared with the backpropagation neural network (BP) and the long-short term memory neural network (LSTM) models, the graph neural network (GNN) model can achieve the improvement rates over 5% for Nash-Sutcliffe efficiency coefficient (NSE) and mean absolute error (MAE) indicators, and the correlation coefficients (R^2) is more than 0.97, while in the dry water cutoff events, the True Positive Rate (TPR) and Precision are generally more than 0.96. GNN has significant advantages in the simulation of hydrological events such as floods and droughts, which can provide a scientific support for the ecological protection of Dongting Lake and its flood control and drought resistance.
Dongting Lake is an important lake in the middle reach of the Yangtze River, and accurately modelling the runoff corresponding relationships of its various input and output stations is crucial for regional ecological protection and flood control and drought defense. To address the complex runoff response relationships in the Dongting Lake basin, this study proposes a multiple-input and multiple-output runoff response model based on graph neural networks. Firstly, the model utilizes the basin topological spatial structure of the Yangtze River, Dongting Lake and Sishui to transform the original observation sequences at each station into graph-structured data to characterize the spatial characteristics of the basin. Secondly, through the mutual correlation analysis method, the time lag relationship between the observed variables at each station is identified to determine the input feature step of the model. Finally, graph neural networks are employed to aggregate and update the features to capture the complex spatial and temporal dependencies among the control station, and to realize the runoff simulation at multiple stations. The results show that in the flood event, compared with the backpropagation neural network (BP) and the long-short term memory neural network (LSTM) models, the graph neural network (GNN) model can achieve the improvement rates over 5% for Nash-Sutcliffe efficiency coefficient (NSE) and mean absolute error (MAE) indicators, and the correlation coefficients (R^2) is more than 0.97, while in the dry water cutoff events, the True Positive Rate (TPR) and Precision are generally more than 0.96. GNN has significant advantages in the simulation of hydrological events such as floods and droughts, which can provide a scientific support for the ecological protection of Dongting Lake and its flood control and drought resistance.
Available online: June 23, 2025
Abstract:
Scientific research on hydrological drought in lake-floodplains and its impact on hydrological connectivity is of great significance for local water resources management and wetland ecological protection. Based on the reconstructed high spatiotemporal resolution inundation datasets from 2000 to 2023 by applying the ESTARFM model (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model), hydrological drought and hydrological connectivity in the Poyang Lake were quantitatively characterized by the standardized inundation area index and the geostatistical hydrological connectivity function, and then their evolution characteristics were analyzed. On this basis, the response of hydrological connectivity to hydrological drought was further clarified by using the methods of STL (Seasonal and Trend decomposition using Loess) time series decomposition and multivariate linear fitting function. The results showed that both annual and interannual variations of hydrological drought in Poyang Lake were complicated, with a high frequency of occurrence and an increasing drought tendency. The hydrological connectivity in the north-south direction of the Poyang Lake is stronger than that in the east-west direction. In recent years, the hydrological connectivity of the Poyang Lake has shown a fluctuating downward trend, which is related to the intensity changes of lake hydrological drought. Further quantitative analysis found that with the increase of the degree of hydrological drought, hydrological connectivity in the Poyang Lake showed a decreasing trend. In the east-west direction, the annual average hydrological connectivity of light drought, medium drought, severe drought and extreme drought in the Poyang Lake can decrease by 45.2%, 50.0%, 54.6% and 70.7%, respectively, compared to no drought scenario. Similarly, in the north-south direction, the annual average hydrological connectivity can decrease by 32.1%, 35.6%, 39.0% and 50.7%, respectively. The changes of hydrological connectivity caused by hydrological drought in the Poyang Lake area will further impact affect the growth and distribution of wetland vegetation, and the results of this study provide scientific basis for the management practice of lake ecosystems under extreme water conditions.
Scientific research on hydrological drought in lake-floodplains and its impact on hydrological connectivity is of great significance for local water resources management and wetland ecological protection. Based on the reconstructed high spatiotemporal resolution inundation datasets from 2000 to 2023 by applying the ESTARFM model (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model), hydrological drought and hydrological connectivity in the Poyang Lake were quantitatively characterized by the standardized inundation area index and the geostatistical hydrological connectivity function, and then their evolution characteristics were analyzed. On this basis, the response of hydrological connectivity to hydrological drought was further clarified by using the methods of STL (Seasonal and Trend decomposition using Loess) time series decomposition and multivariate linear fitting function. The results showed that both annual and interannual variations of hydrological drought in Poyang Lake were complicated, with a high frequency of occurrence and an increasing drought tendency. The hydrological connectivity in the north-south direction of the Poyang Lake is stronger than that in the east-west direction. In recent years, the hydrological connectivity of the Poyang Lake has shown a fluctuating downward trend, which is related to the intensity changes of lake hydrological drought. Further quantitative analysis found that with the increase of the degree of hydrological drought, hydrological connectivity in the Poyang Lake showed a decreasing trend. In the east-west direction, the annual average hydrological connectivity of light drought, medium drought, severe drought and extreme drought in the Poyang Lake can decrease by 45.2%, 50.0%, 54.6% and 70.7%, respectively, compared to no drought scenario. Similarly, in the north-south direction, the annual average hydrological connectivity can decrease by 32.1%, 35.6%, 39.0% and 50.7%, respectively. The changes of hydrological connectivity caused by hydrological drought in the Poyang Lake area will further impact affect the growth and distribution of wetland vegetation, and the results of this study provide scientific basis for the management practice of lake ecosystems under extreme water conditions.
Available online: June 19, 2025
Abstract:
Dissolved organic matter (DOM) is a kind of substances with various structural compositions, complex physicochemical properties and wide molecular weight distribution, which mainly contains humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acid, hydroxyl, phenolic, aldehyde and other reactive groups, etc. DOM exists widely in lake ecosystems, and it can participate in a variety of biogeochemical processes, influence the migration transformation and behavior of biotic elements and pollutants, and play an important role in the conversion of carbon sinks in ecosystems. DOM in lake water has various environmental behaviors. For example, DOM can be adsorbed to the surface of water particles, and the distribution of DOM in the dissolved/suspended phase can be regulated; DOM in lakes will undergo photo- and microbial degradation, which will change the content and structural composition of DOM samples; the multifunctional groups in DOM in lakes can be easily complexed with metal ions, and can also undergo electron transfer to produce reactive oxygen species. In addition, lake DOM also has significant ecological and environmental effects. DOM can be loaded on the surface of colloidal particles, affecting the stability of colloidal particles and transparency of the water body; DOM binding with heavy metals will change the bioavailability of heavy metal and the health of lake ecosystems; lake DOM can promote organic pollutant degradation through the mediating role of reactive oxygen species, or inhibit pollutant degradation through the role of light shielding. It should be pointed out that the behavior and ecological effects of lake DOM are closely related to its molecular weight, active group and molecular structure. In this paper, we systematically review the behavior and ecological effects of lake DOM and its correlation with the molecular structure compositions. Results obtained can provide theoretical guidance and technical support for the process and mechanism of lake pollution, lake restoration and regulation, lake management and planning.
Dissolved organic matter (DOM) is a kind of substances with various structural compositions, complex physicochemical properties and wide molecular weight distribution, which mainly contains humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acid, hydroxyl, phenolic, aldehyde and other reactive groups, etc. DOM exists widely in lake ecosystems, and it can participate in a variety of biogeochemical processes, influence the migration transformation and behavior of biotic elements and pollutants, and play an important role in the conversion of carbon sinks in ecosystems. DOM in lake water has various environmental behaviors. For example, DOM can be adsorbed to the surface of water particles, and the distribution of DOM in the dissolved/suspended phase can be regulated; DOM in lakes will undergo photo- and microbial degradation, which will change the content and structural composition of DOM samples; the multifunctional groups in DOM in lakes can be easily complexed with metal ions, and can also undergo electron transfer to produce reactive oxygen species. In addition, lake DOM also has significant ecological and environmental effects. DOM can be loaded on the surface of colloidal particles, affecting the stability of colloidal particles and transparency of the water body; DOM binding with heavy metals will change the bioavailability of heavy metal and the health of lake ecosystems; lake DOM can promote organic pollutant degradation through the mediating role of reactive oxygen species, or inhibit pollutant degradation through the role of light shielding. It should be pointed out that the behavior and ecological effects of lake DOM are closely related to its molecular weight, active group and molecular structure. In this paper, we systematically review the behavior and ecological effects of lake DOM and its correlation with the molecular structure compositions. Results obtained can provide theoretical guidance and technical support for the process and mechanism of lake pollution, lake restoration and regulation, lake management and planning.
Available online: June 19, 2025
Abstract:
Lake-reservoir type water sources are crucial to China’s water supply, playing a vital role in ensuring regional water security. This study focused on the Panjiakou Reservoir, a key water source for the Luanhe-Tianjin Water Diversion Project. A three-dimensional numerical model was performed to unveil the response of bottom hypoxia under varying reservoir operations and nitrate concentrations in the inflow. Based on these findings, we proposed comprehensive strategies for preventing and controlling bottom hypoxia. In this paper, the measured reservoir data from 2017 to 2018 were used to verify the reliability of the model. Results show that increasing the reservoir"s outflow significantly shortened the duration of bottom hypoxia and weakened its severity in the later stage of thermal stratification. Moreover, a substantial reduction in the nitrate concentration in the inflow resulted in a significant increase in the duration, severity, and spatial extent of bottom hypoxia. Based on the actual operation of the reservoir and the requirements for meeting the standards of water supply quality, this article suggests: 1) joint scheduling with the downstream Daheiting Reservoir should be implemented, adjusting the outflow volumes during January-April and September-December to concentrate the discharge in mid-to-late October. This optimization reduced the duration of severe hypoxia and the maximum hypoxic area by 54% and 23%, respectively. 2) Second, we recommended reducing the upstream nitrate concentration to 1.5-2 mg/L as part of the watershed pollution control efforts. This approach ensured that the total nitrogen (TN) concentration in the discharged water satisfied the standards, while maximizing the mitigating effect of nitrate on bottom hypoxia. Our study proposed a comprehensive strategy for reservoir water quality protection from multiple perspectives, including "upstream pollution source concentration control, reservoir hypoxia prevention, and downstream water quality standards compliance", which were of importance for the protection and restoration of aquatic environments in the deep water source reservoirs.
Lake-reservoir type water sources are crucial to China’s water supply, playing a vital role in ensuring regional water security. This study focused on the Panjiakou Reservoir, a key water source for the Luanhe-Tianjin Water Diversion Project. A three-dimensional numerical model was performed to unveil the response of bottom hypoxia under varying reservoir operations and nitrate concentrations in the inflow. Based on these findings, we proposed comprehensive strategies for preventing and controlling bottom hypoxia. In this paper, the measured reservoir data from 2017 to 2018 were used to verify the reliability of the model. Results show that increasing the reservoir"s outflow significantly shortened the duration of bottom hypoxia and weakened its severity in the later stage of thermal stratification. Moreover, a substantial reduction in the nitrate concentration in the inflow resulted in a significant increase in the duration, severity, and spatial extent of bottom hypoxia. Based on the actual operation of the reservoir and the requirements for meeting the standards of water supply quality, this article suggests: 1) joint scheduling with the downstream Daheiting Reservoir should be implemented, adjusting the outflow volumes during January-April and September-December to concentrate the discharge in mid-to-late October. This optimization reduced the duration of severe hypoxia and the maximum hypoxic area by 54% and 23%, respectively. 2) Second, we recommended reducing the upstream nitrate concentration to 1.5-2 mg/L as part of the watershed pollution control efforts. This approach ensured that the total nitrogen (TN) concentration in the discharged water satisfied the standards, while maximizing the mitigating effect of nitrate on bottom hypoxia. Our study proposed a comprehensive strategy for reservoir water quality protection from multiple perspectives, including "upstream pollution source concentration control, reservoir hypoxia prevention, and downstream water quality standards compliance", which were of importance for the protection and restoration of aquatic environments in the deep water source reservoirs.
Available online: June 18, 2025
Abstract:
Abstract: The construction of the Three Gorges Dam has significantly altered water and sediment fluxes in the Yangtze River, yet its impact on microbially mediated multifunctionality (carbon, nitrogen, and phosphorus cycling) in sediments remains unclear. This study employed 16S amplicon sequencing, co-occurrence network analysis, and structural equation modeling to investigate the effects of the dam on bacterial community composition, diversity, and multifunctionality in upstream and downstream sediments. Results revealed that upstream sediments were dominated by Proteobacteria (~25.5%), while downstream sediments were dominated by Desulfobacterota (~24.8%). The dam significantly reduced bacterial α-diversity in downstream sediments, which was closely correlated with reductions in moisture (~35.4%), cation exchange capacity (~49.6%), and dissolved organic carbon (~49.9%). Structural equation modeling indicated that reduced α-diversity directly impaired ecological functions and indirectly decreased multifunctionality by weakening bacterial network interactions. This study highlights the adverse ecological impacts of the Three Gorges Dam on downstream sediment functions and recommends long-term monitoring of dissolved organic carbon and cation exchange capacity, alongside optimized reservoir management, to mitigate biodiversity loss.
Abstract: The construction of the Three Gorges Dam has significantly altered water and sediment fluxes in the Yangtze River, yet its impact on microbially mediated multifunctionality (carbon, nitrogen, and phosphorus cycling) in sediments remains unclear. This study employed 16S amplicon sequencing, co-occurrence network analysis, and structural equation modeling to investigate the effects of the dam on bacterial community composition, diversity, and multifunctionality in upstream and downstream sediments. Results revealed that upstream sediments were dominated by Proteobacteria (~25.5%), while downstream sediments were dominated by Desulfobacterota (~24.8%). The dam significantly reduced bacterial α-diversity in downstream sediments, which was closely correlated with reductions in moisture (~35.4%), cation exchange capacity (~49.6%), and dissolved organic carbon (~49.9%). Structural equation modeling indicated that reduced α-diversity directly impaired ecological functions and indirectly decreased multifunctionality by weakening bacterial network interactions. This study highlights the adverse ecological impacts of the Three Gorges Dam on downstream sediment functions and recommends long-term monitoring of dissolved organic carbon and cation exchange capacity, alongside optimized reservoir management, to mitigate biodiversity loss.
Available online: June 18, 2025
Abstract:
As an emerging solution to address fish passage challenges in high dams, the fish collection and transportation system was first implemented in China in the early 21st century at several high-head hydropower stations. However, limited data have been reported on its effectiveness. The Wudongde Hydropower Station pioneered a tailrace outlet fish collection scheme, constructing a fish collection and transportation system to assist fish migration. Based on fish collection data from the Wudongde fish collection and transportation system from 2021 to 2023, this study analyzed the characteristics of collected fish using Diversity index, Index of relative importance, Fish autecology matrix , and Ward clustering. The results were cross-validated with environmental impact assessment and design requirements to preliminarily evaluate the system’s efficacy. During 2021–2023, the Wudongde fish collection and transportation system collected 95,281 individuals from 52 fish species. Statistical analyses revealed: (1) All 10 main and secondary fish passing objects were collected, with Percocypris pingi exhibiting the largest average size. (2) The collected specimens of Coreius guichenoti, Rhinogobio ventralis, Jinshaia sinensis, Leptobotia elongata, and Schizothoracinae fishes were mainly 4-year-old, 3-year-old, 6-year-old, 4-year-old, and 4-year-old, respectively. (3) Fish diversity indices indicated moderate overall diversity and a relatively simple community structure. (4) Dominant species included Hemiculter leucisculus, Botia superciliaris, and Pseudogyrinocheilus procheilus, collectively accounting for 87.3% of the total catch. (5) At the species level, Sticky and demersal eggs，Settlement were predominant. Lotic type species dominated, but lentic type also comprised a notable proportion. (6) Ward clustering showed distinct seasonal differences, with July and August forming separate clusters due to high collection volumes, while other months grouped into another cluster. Overall, the Wudongde fish collection and transportation system facilitated migration for most fish species in the river section, with no size-selective bias observed. Preliminary assessment suggests that the majority of the main and secondary fish passing objects collected are potential breeding populations that have reached the age of first sexual maturity. Compared with the breeding time proposed in the environmental impact assessment and design stage, the collection month of some fish objects is delayed or advanced, and the change of fish composition is basically in line with the prediction in the design stage. Compared to similar fish passage facilities, the Wudongde fish collection and transportation system demonstrated superior efficacy by utilizing turbine tailwater for fish attraction, effectively mitigating the hydropower station’s barrier effects. Future efforts should optimize system operations, enhance monitoring, and scientifically evaluate its effectiveness to promote connectivity restoration in the lower Jinsha River.
As an emerging solution to address fish passage challenges in high dams, the fish collection and transportation system was first implemented in China in the early 21st century at several high-head hydropower stations. However, limited data have been reported on its effectiveness. The Wudongde Hydropower Station pioneered a tailrace outlet fish collection scheme, constructing a fish collection and transportation system to assist fish migration. Based on fish collection data from the Wudongde fish collection and transportation system from 2021 to 2023, this study analyzed the characteristics of collected fish using Diversity index, Index of relative importance, Fish autecology matrix , and Ward clustering. The results were cross-validated with environmental impact assessment and design requirements to preliminarily evaluate the system’s efficacy. During 2021–2023, the Wudongde fish collection and transportation system collected 95,281 individuals from 52 fish species. Statistical analyses revealed: (1) All 10 main and secondary fish passing objects were collected, with Percocypris pingi exhibiting the largest average size. (2) The collected specimens of Coreius guichenoti, Rhinogobio ventralis, Jinshaia sinensis, Leptobotia elongata, and Schizothoracinae fishes were mainly 4-year-old, 3-year-old, 6-year-old, 4-year-old, and 4-year-old, respectively. (3) Fish diversity indices indicated moderate overall diversity and a relatively simple community structure. (4) Dominant species included Hemiculter leucisculus, Botia superciliaris, and Pseudogyrinocheilus procheilus, collectively accounting for 87.3% of the total catch. (5) At the species level, Sticky and demersal eggs，Settlement were predominant. Lotic type species dominated, but lentic type also comprised a notable proportion. (6) Ward clustering showed distinct seasonal differences, with July and August forming separate clusters due to high collection volumes, while other months grouped into another cluster. Overall, the Wudongde fish collection and transportation system facilitated migration for most fish species in the river section, with no size-selective bias observed. Preliminary assessment suggests that the majority of the main and secondary fish passing objects collected are potential breeding populations that have reached the age of first sexual maturity. Compared with the breeding time proposed in the environmental impact assessment and design stage, the collection month of some fish objects is delayed or advanced, and the change of fish composition is basically in line with the prediction in the design stage. Compared to similar fish passage facilities, the Wudongde fish collection and transportation system demonstrated superior efficacy by utilizing turbine tailwater for fish attraction, effectively mitigating the hydropower station’s barrier effects. Future efforts should optimize system operations, enhance monitoring, and scientifically evaluate its effectiveness to promote connectivity restoration in the lower Jinsha River.
Available online: June 16, 2025
Abstract:
The operation of the Three Gorges Project led to significant channel adjustments in the downstream reaches, and thus changed the diversion patterns of flow and sediment in bifurcated reaches, which had a significant impact on flood control, navigation, water diversion, and ecology. This study investigated the variation characteristics of four distinct bifurcated reaches in the reach between Jianli and Shijitou of the Middle Yangtze River. Using a two-dimensional flow-sediment transport model, this study compared the flow and sediment diversion ratios before and after the reservoir operation under different flow regimes, and consequently identified the drivers behind the variation in diversion patterns. The results demonstrate that during the post-operation period, the straight bifurcated reach underwent erosion and deposition, while both the main and second branches of the curved bifurcated reach underwent erosion, primarily occurring in the low-water channels. River regulation projects prevented the retreat of high floodplain of the mid-channel bar (MCB) and caused the deposition of low floodplain of the MCB. The channels with higher erosion intensity evolved into the main branches, causing the shift in the main and second branches of some bifurcated reaches. The low-discharge diversion ratios in the right branch of the bifurcated reaches of Nanmenzhou and Luxikou increased from 0.42 and 0.40 to 0.95 and 0.81, respectively, with both showing an increase of over 100%. The imbalanced erosion in the bifurcated reaches is the primary cause for the variation in flow and sediment diversion patterns, with the impact decreasing for a higher discharge. For every 1.0 m increase in the relative scour depth between the main and secondary branch, the flow diversion ratio of the main branch would increase by approximately 7.6–15.8%, and the sediment diversion ratio would increase by approximately 8.2–11.8%. Changes in the mid-channel bar planform would further influence the flow diversion patterns. Sediment deposition on the low floodplain was adverse to the inflow entering the left branch of the Nanyangzhou reach, while the retreat of the high floodplain in the left branch further decreased the flow diversion ratio under the medium to high discharge conditions.
The operation of the Three Gorges Project led to significant channel adjustments in the downstream reaches, and thus changed the diversion patterns of flow and sediment in bifurcated reaches, which had a significant impact on flood control, navigation, water diversion, and ecology. This study investigated the variation characteristics of four distinct bifurcated reaches in the reach between Jianli and Shijitou of the Middle Yangtze River. Using a two-dimensional flow-sediment transport model, this study compared the flow and sediment diversion ratios before and after the reservoir operation under different flow regimes, and consequently identified the drivers behind the variation in diversion patterns. The results demonstrate that during the post-operation period, the straight bifurcated reach underwent erosion and deposition, while both the main and second branches of the curved bifurcated reach underwent erosion, primarily occurring in the low-water channels. River regulation projects prevented the retreat of high floodplain of the mid-channel bar (MCB) and caused the deposition of low floodplain of the MCB. The channels with higher erosion intensity evolved into the main branches, causing the shift in the main and second branches of some bifurcated reaches. The low-discharge diversion ratios in the right branch of the bifurcated reaches of Nanmenzhou and Luxikou increased from 0.42 and 0.40 to 0.95 and 0.81, respectively, with both showing an increase of over 100%. The imbalanced erosion in the bifurcated reaches is the primary cause for the variation in flow and sediment diversion patterns, with the impact decreasing for a higher discharge. For every 1.0 m increase in the relative scour depth between the main and secondary branch, the flow diversion ratio of the main branch would increase by approximately 7.6–15.8%, and the sediment diversion ratio would increase by approximately 8.2–11.8%. Changes in the mid-channel bar planform would further influence the flow diversion patterns. Sediment deposition on the low floodplain was adverse to the inflow entering the left branch of the Nanyangzhou reach, while the retreat of the high floodplain in the left branch further decreased the flow diversion ratio under the medium to high discharge conditions.
Available online: June 16, 2025
Abstract:
Frequent outbreaks of Cladophora blooms in the newly formed littoral zone of Qinghai Lake have been observed due to the warming and humidification of the Qinghai-Tibet Plateau climate. Previous studies on the extraction of Cladophora blooms mainly relied on multi-source satellite remote sensing imagery. However, the limitations of image spatial resolution and mixed-pixel effects hindered the accurate identification of the true distribution and detailed features of the blooms. This study utilized low-altitude UAV imagery combined with the Attention DeepLab V3+ deep learning model to automatically extract Cladophora bloom features in Qinghai Lake. A comparative analysis was conducted with results derived from spectral indice and machine learning methods, and the differences between UAV imagery and optical satellite remote sensing imagery in extracting Cladophora blooms were explored. The results revealed the following: (1) Attention DeepLab V3+ could accurately detect Cladophora blooms without prior thresholds, achieving a kappa coefficient, precision, recall, and F1 score of 0.985, 0.969, 0.983, and 0.976, respectively. (2) Compared with existing methods, the model’s kappa coefficient and F1 score improved by 4.47%-29.75% and 6.35%-34.02%, respectively, demonstrating superior adaptability to complex bloom distribution patterns, especially in capturing boundary details and separating voids. (3) Optical satellite remote sensing imagery tended to overestimate Cladophora blooms in Qinghai Lake, with mean relative error values ranging from 5.5% to 323.47%. This study leveraged the high-resolution advantages of UAV imagery to provide technical support for accurately assessing the true distribution of Cladophora blooms in Qinghai Lake and laid a foundation for the monitoring and tracking of algal blooms features in other water bodies.
Frequent outbreaks of Cladophora blooms in the newly formed littoral zone of Qinghai Lake have been observed due to the warming and humidification of the Qinghai-Tibet Plateau climate. Previous studies on the extraction of Cladophora blooms mainly relied on multi-source satellite remote sensing imagery. However, the limitations of image spatial resolution and mixed-pixel effects hindered the accurate identification of the true distribution and detailed features of the blooms. This study utilized low-altitude UAV imagery combined with the Attention DeepLab V3+ deep learning model to automatically extract Cladophora bloom features in Qinghai Lake. A comparative analysis was conducted with results derived from spectral indice and machine learning methods, and the differences between UAV imagery and optical satellite remote sensing imagery in extracting Cladophora blooms were explored. The results revealed the following: (1) Attention DeepLab V3+ could accurately detect Cladophora blooms without prior thresholds, achieving a kappa coefficient, precision, recall, and F1 score of 0.985, 0.969, 0.983, and 0.976, respectively. (2) Compared with existing methods, the model’s kappa coefficient and F1 score improved by 4.47%-29.75% and 6.35%-34.02%, respectively, demonstrating superior adaptability to complex bloom distribution patterns, especially in capturing boundary details and separating voids. (3) Optical satellite remote sensing imagery tended to overestimate Cladophora blooms in Qinghai Lake, with mean relative error values ranging from 5.5% to 323.47%. This study leveraged the high-resolution advantages of UAV imagery to provide technical support for accurately assessing the true distribution of Cladophora blooms in Qinghai Lake and laid a foundation for the monitoring and tracking of algal blooms features in other water bodies.
Available online: June 13, 2025
Abstract:
Lake Taihu is a large eutrophication lake, the endogenous pollution and release characteristics of sediments in different lake areas were significantly different. The study investigated and analyzed the variation of endogenous pollution and nitrogen and phosphorus diffusion fluxes in Xuhu (grass-dominated zone) and Zhushan Bay(algae-dominated zone) with different water depths. The results showed that: The total nitrogen content in the sediments of Xuhu Lake and Zhushan Lake was 2.59~3.33g·kg-1 and 2.95~3.63g·kg-1, and the total phosphorus content was 0.462~0.652g·kg-1 and 0.749~0.916g·kg-1, respectively. The nutrient content in the sediments of the algae lake area was significantly higher than that in the grass lake area, and the content fluctuated irregularly with the change of water depth. Phosphorus speciation analysis of sediments showed that: Ca-P were the main sediments in Xuhu Bay, and the proportion of Ca-P in total phosphorus decreased significantly with the increase of water depth.The phosphorus morphology in the sediments of Zhushan Lake was dominated by Fe-P, and the proportions of Fe-P, Al-P and Ca-P in the total phosphorus gradually increased with the increase of water depth. The SRP content at the sediment-water interface in the shallow water area of Xuhu is significantly higher than that in the deep water area, while the difference in Fe2+ and NH4+ concentrations between different water depths is relatively small. The SRP, Fe2+ and NH4+ contents at the sediment-water interface in the shallow water area of Zhu Mountain Lake are all higher than those in the deep water area.The endogenous release risk of Xuhu and Zhushan Lake was small, and the NH4+ diffusion flux of Xuhu Lake decreased first and then increased with the increase of water depth, and the NH4+ diffusion flux of Zhushan Lake increased significantly with the increase of water depth. The results play an important role in understanding the nitrogen and phosphorus migration of water depth at the sediment-water interface in the grass/algae lake area of Taihu Lake.
Lake Taihu is a large eutrophication lake, the endogenous pollution and release characteristics of sediments in different lake areas were significantly different. The study investigated and analyzed the variation of endogenous pollution and nitrogen and phosphorus diffusion fluxes in Xuhu (grass-dominated zone) and Zhushan Bay(algae-dominated zone) with different water depths. The results showed that: The total nitrogen content in the sediments of Xuhu Lake and Zhushan Lake was 2.59~3.33g·kg-1 and 2.95~3.63g·kg-1, and the total phosphorus content was 0.462~0.652g·kg-1 and 0.749~0.916g·kg-1, respectively. The nutrient content in the sediments of the algae lake area was significantly higher than that in the grass lake area, and the content fluctuated irregularly with the change of water depth. Phosphorus speciation analysis of sediments showed that: Ca-P were the main sediments in Xuhu Bay, and the proportion of Ca-P in total phosphorus decreased significantly with the increase of water depth.The phosphorus morphology in the sediments of Zhushan Lake was dominated by Fe-P, and the proportions of Fe-P, Al-P and Ca-P in the total phosphorus gradually increased with the increase of water depth. The SRP content at the sediment-water interface in the shallow water area of Xuhu is significantly higher than that in the deep water area, while the difference in Fe2+ and NH4+ concentrations between different water depths is relatively small. The SRP, Fe2+ and NH4+ contents at the sediment-water interface in the shallow water area of Zhu Mountain Lake are all higher than those in the deep water area.The endogenous release risk of Xuhu and Zhushan Lake was small, and the NH4+ diffusion flux of Xuhu Lake decreased first and then increased with the increase of water depth, and the NH4+ diffusion flux of Zhushan Lake increased significantly with the increase of water depth. The results play an important role in understanding the nitrogen and phosphorus migration of water depth at the sediment-water interface in the grass/algae lake area of Taihu Lake.
Available online: June 11, 2025
Abstract:
The Chaobai River basin, a biodiversity hotspot in Beijing, plays a crucial role in understanding the river"s ecosystem and improving protection quality through studies on large benthic animal biodiversity and community stability. In this study, 44 sampling sites were set up in the mountainous and plain sections of the Chaobai River basin, and surveys of large benthic animal communities and their diversity were conducted in September 2020 (autumn), December 2020 (winter), April 2021 (spring), and July 2021 (summer). Using data from these surveys, we analyzed the spatiotemporal changes in multidimensional biodiversity and community stability of benthic animals in the Chaobai River basin and explored the relationships between various biodiversity and community stability indices using Pearson correlation coefficients and generalized linear models. Results showed that seasonal changes in biodiversity and community stability of benthic animals in the Chaobai River were not significant, while differences between mountainous and plain areas were pronounced. The Margalef richness index and other species diversity indices were higher in the mountainous area, but the Pielou evenness index was lower. Functional diversity indices indicated richer functional traits and more redundant species in the mountainous section. Secondary productivity, turnover rate, and species competition intensity of benthic animals were lower in the mountainous area of the Chaobai River than in the plain area, while cohesion was higher, suggesting greater community stability in the mountainous area. Pearson correlation analysis revealed significant correlations between different biodiversity indices, while correlations between indices representing community stability were weak and not significant (p>0.05). Analysis of the correlation between diversity and stability found that more uniform species distribution, higher species richness, and greater niche differentiation led to higher secondary productivity, larger turnover rate, less species competition, and greater community cohesion, resulting in higher community stability. The most parsimonious models for community stability in both mountainous and plain areas favored taxonomic and functional diversity to explain changes in benthic animal community stability in the Chaobai River. Functional divergence (FDiv) was selected most frequently, indicating that differences in species trait abundance and interspecific niche complementarity are key factors affecting benthic animal community stability in the Chaobai River. However, only the model for secondary productivity in the plain area had relatively high explanatory power, while other models had low explanatory power, suggesting that long-term environmental factors may have a greater impact on benthic animal community stability in the Chaobai River.
The Chaobai River basin, a biodiversity hotspot in Beijing, plays a crucial role in understanding the river"s ecosystem and improving protection quality through studies on large benthic animal biodiversity and community stability. In this study, 44 sampling sites were set up in the mountainous and plain sections of the Chaobai River basin, and surveys of large benthic animal communities and their diversity were conducted in September 2020 (autumn), December 2020 (winter), April 2021 (spring), and July 2021 (summer). Using data from these surveys, we analyzed the spatiotemporal changes in multidimensional biodiversity and community stability of benthic animals in the Chaobai River basin and explored the relationships between various biodiversity and community stability indices using Pearson correlation coefficients and generalized linear models. Results showed that seasonal changes in biodiversity and community stability of benthic animals in the Chaobai River were not significant, while differences between mountainous and plain areas were pronounced. The Margalef richness index and other species diversity indices were higher in the mountainous area, but the Pielou evenness index was lower. Functional diversity indices indicated richer functional traits and more redundant species in the mountainous section. Secondary productivity, turnover rate, and species competition intensity of benthic animals were lower in the mountainous area of the Chaobai River than in the plain area, while cohesion was higher, suggesting greater community stability in the mountainous area. Pearson correlation analysis revealed significant correlations between different biodiversity indices, while correlations between indices representing community stability were weak and not significant (p>0.05). Analysis of the correlation between diversity and stability found that more uniform species distribution, higher species richness, and greater niche differentiation led to higher secondary productivity, larger turnover rate, less species competition, and greater community cohesion, resulting in higher community stability. The most parsimonious models for community stability in both mountainous and plain areas favored taxonomic and functional diversity to explain changes in benthic animal community stability in the Chaobai River. Functional divergence (FDiv) was selected most frequently, indicating that differences in species trait abundance and interspecific niche complementarity are key factors affecting benthic animal community stability in the Chaobai River. However, only the model for secondary productivity in the plain area had relatively high explanatory power, while other models had low explanatory power, suggesting that long-term environmental factors may have a greater impact on benthic animal community stability in the Chaobai River.
Available online: June 11, 2025
Abstract:
This study quantifies the spatiotemporal dynamics of blue and green water resources in the Min-Tuo River Basin and disentangles their differential sensitivities to climate and land-use changes, thereby proposing context-specific management strategies and adaptive pathways for sustainable water governance.Utilizing the Soil and Water Assessment Tool (SWAT) model and the Future Land-Use Simulation (FLUS) model, combined with climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6),we analyzed historical changes (1981–2021) and projected future dynamics of blue and green water up to 2100. Key findings include:(1)From 1981 to 2021, the Min-Tuo River Basin was dominated by blue water, accounting for 63.2% of the total water resources. Climate change served as the core driving factor for variations in blue and green water, with contribution rates of 79.12% and 63.29%, respectively.(2)Between 1990 and 2020, cultivated land and grassland decreased by 4.0% and 2.1% , respectively, while urban land expanded by 138% , significantly reducing agricultural and grassland areas and exacerbating spatial imbalances in water resources.By 2040, urban land is projected to further expand by 135% , further compressing the spatial extent of grassland and cultivated land. This expansion will concentrate in the Chengdu Plain?in the eastern part of the basin, exacerbating water scarcity risks in densely populated areas.(3)Future climate trends indicate a precipitation increase of 1.43-1.80 mm/a,temperature rise of 0.025-0.042℃/a,Green water will significantly increase by 0.35-1.02 mm/a, while blue water decreases until 2050 before rebounding. Among the four Shared Socioeconomic Pathways (SSPs), the fossil fuel-dominated pathway (SSP5-8.5) exhibits the most pronounced changes in blue and green water, whereas curbing urban expansion and prioritizing sustainable development (SSP1-2.6) could effectively alleviate water resource pressure.(4)blue water concentrates in the southwestern basin, while green water hotspots shift southeastward. The Chengdu Plain faces heightened risks of water scarcity and extreme events due to population density and elevated temperatures.This study provides a scientific basis for adaptive water management strategies in the Min-Tuo River Basin under climate and land-use pressures.
This study quantifies the spatiotemporal dynamics of blue and green water resources in the Min-Tuo River Basin and disentangles their differential sensitivities to climate and land-use changes, thereby proposing context-specific management strategies and adaptive pathways for sustainable water governance.Utilizing the Soil and Water Assessment Tool (SWAT) model and the Future Land-Use Simulation (FLUS) model, combined with climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6),we analyzed historical changes (1981–2021) and projected future dynamics of blue and green water up to 2100. Key findings include:(1)From 1981 to 2021, the Min-Tuo River Basin was dominated by blue water, accounting for 63.2% of the total water resources. Climate change served as the core driving factor for variations in blue and green water, with contribution rates of 79.12% and 63.29%, respectively.(2)Between 1990 and 2020, cultivated land and grassland decreased by 4.0% and 2.1% , respectively, while urban land expanded by 138% , significantly reducing agricultural and grassland areas and exacerbating spatial imbalances in water resources.By 2040, urban land is projected to further expand by 135% , further compressing the spatial extent of grassland and cultivated land. This expansion will concentrate in the Chengdu Plain?in the eastern part of the basin, exacerbating water scarcity risks in densely populated areas.(3)Future climate trends indicate a precipitation increase of 1.43-1.80 mm/a,temperature rise of 0.025-0.042℃/a,Green water will significantly increase by 0.35-1.02 mm/a, while blue water decreases until 2050 before rebounding. Among the four Shared Socioeconomic Pathways (SSPs), the fossil fuel-dominated pathway (SSP5-8.5) exhibits the most pronounced changes in blue and green water, whereas curbing urban expansion and prioritizing sustainable development (SSP1-2.6) could effectively alleviate water resource pressure.(4)blue water concentrates in the southwestern basin, while green water hotspots shift southeastward. The Chengdu Plain faces heightened risks of water scarcity and extreme events due to population density and elevated temperatures.This study provides a scientific basis for adaptive water management strategies in the Min-Tuo River Basin under climate and land-use pressures.
Available online: June 09, 2025
Abstract:
To investigate the impact of fluoride pollution on bacterial communities in the water-soil system, this study collected 66 sets of surface water, sediment, and riparian soil samples from the Qingshui River basin in Ningxia in 2022. The samples were categorized into three groups based on the fluoride concentration in the surface water: low fluoride group (F? < 1.0 mg/L), high fluoride I group (1.0 ≤ F? < 1.5 mg/L), and high fluoride II group (F? ≥ 1.5 mg/L). Bacterial community responses were systematically analyzed through 16S rDNA high-throughput sequencing and polymorphic fluoride species analysis. The results revealed that fluoride pollution decreased bacterial α-diversity (low fluoride group > high fluoride I group > high fluoride II group), although the Chao1 index of sediments increased due to niche release by rare species. The phyla Campilobacterota and Desulfobacterota were identified as fluoride-tolerant bacterial phyla, with species of Desulfobacterota participating in sulfate reduction to alleviate fluoride toxicity at low abundances. Genera such as Sulfurovum were recognized as fluoride-tolerant bacterial genera in the water-soil system. Bacteria facilitated the conversion of residual fixed fluoride (Res-F) in sediments and soils by decomposing and transforming it into other forms, with soil environments proving more favorable for bacterial decomposition of Res-F. This study establishes the first framework linking bacterial communities to polymorphic fluoride in the Qingshui River basin, enhancing the understanding of the impact of fluoride on bacterial communities in river ecosystems. It provides a scientific basis for the development of effective ecological and environmental protection policies, contributing to mitigating or reducing the potential risks of fluoride pollution to the ecological environment.
To investigate the impact of fluoride pollution on bacterial communities in the water-soil system, this study collected 66 sets of surface water, sediment, and riparian soil samples from the Qingshui River basin in Ningxia in 2022. The samples were categorized into three groups based on the fluoride concentration in the surface water: low fluoride group (F? < 1.0 mg/L), high fluoride I group (1.0 ≤ F? < 1.5 mg/L), and high fluoride II group (F? ≥ 1.5 mg/L). Bacterial community responses were systematically analyzed through 16S rDNA high-throughput sequencing and polymorphic fluoride species analysis. The results revealed that fluoride pollution decreased bacterial α-diversity (low fluoride group > high fluoride I group > high fluoride II group), although the Chao1 index of sediments increased due to niche release by rare species. The phyla Campilobacterota and Desulfobacterota were identified as fluoride-tolerant bacterial phyla, with species of Desulfobacterota participating in sulfate reduction to alleviate fluoride toxicity at low abundances. Genera such as Sulfurovum were recognized as fluoride-tolerant bacterial genera in the water-soil system. Bacteria facilitated the conversion of residual fixed fluoride (Res-F) in sediments and soils by decomposing and transforming it into other forms, with soil environments proving more favorable for bacterial decomposition of Res-F. This study establishes the first framework linking bacterial communities to polymorphic fluoride in the Qingshui River basin, enhancing the understanding of the impact of fluoride on bacterial communities in river ecosystems. It provides a scientific basis for the development of effective ecological and environmental protection policies, contributing to mitigating or reducing the potential risks of fluoride pollution to the ecological environment.
Available online: May 14, 2025
Abstract:
As a representative subtropical plateau wetland ecosystem in China, Caohai Lake is characterized by abundant aquatic flora and fauna resources and high ecological value. However, recent intensification of eutrophication has triggered massive decline of submerged macrophytes, driving the gradual regime shift from a macrophyte-dominated clear-water state to an algae-dominated turbid-water state, profoundly impacting ecosystem functions and biodiversity. Based on field investigations conducted during 2022-2023, this study systematically examined the current status and characteristics of macroinvertebrate communities in Caohai Lake, comparing differences with historical data from macrophyte-dominated periods (1983 and 2014), thereby revealing the response mechanisms of macroinvertebrate communities during the regime shift. Results showed that current macroinvertebrate communities exhibited a mean density of 146.49 ± 16.62 ind./m2 and biomass of 15.93 ± 14.02 g/m2, with Shannon-Weiner diversity index (0.73 ± 0.06), Margalef richness index (0.37 ± 0.03), and Pielou evenness index (0.66 ± 0.04). Functional feeding groups comprised 94.69% collectors, 2.81% predators, 1.58% scrapers, and 0.92% filter-feeders. Spatial distribution patterns of macroinvertebrate communities corresponded with submerged macrophyte distribution. Biomass showed significant seasonal variation (p < 0.05), being higher in autumn and winter than spring and summer, while other community characteristics exhibited no significant seasonal differences. Redundancy analysis identified dissolved oxygen (DO), water depth (WD), pH, permanganate index (CODMn), transparency (SD), and conductivity (Cond) as key environmental drivers. Over two decades, CODMn showed persistent increase while Chl.a concentration rose and SD declined annually post-regime shift. Comparative analysis revealed dominance of scrapers (Gastropoda) during the clear-water state versus gather-collectors (Tubificidae and Chironomidae) in the turbid-water state, with higher species richness, density, biomass, and diversity indices observed during the macrophyte-dominated phase. This study provides critical scientific basis for comprehensive assessment of Caohai Lake"s aquatic ecosystem status, understanding macroinvertebrate responses during plateau lake regime shifts, and implementing targeted ecological restoration measures.
As a representative subtropical plateau wetland ecosystem in China, Caohai Lake is characterized by abundant aquatic flora and fauna resources and high ecological value. However, recent intensification of eutrophication has triggered massive decline of submerged macrophytes, driving the gradual regime shift from a macrophyte-dominated clear-water state to an algae-dominated turbid-water state, profoundly impacting ecosystem functions and biodiversity. Based on field investigations conducted during 2022-2023, this study systematically examined the current status and characteristics of macroinvertebrate communities in Caohai Lake, comparing differences with historical data from macrophyte-dominated periods (1983 and 2014), thereby revealing the response mechanisms of macroinvertebrate communities during the regime shift. Results showed that current macroinvertebrate communities exhibited a mean density of 146.49 ± 16.62 ind./m2 and biomass of 15.93 ± 14.02 g/m2, with Shannon-Weiner diversity index (0.73 ± 0.06), Margalef richness index (0.37 ± 0.03), and Pielou evenness index (0.66 ± 0.04). Functional feeding groups comprised 94.69% collectors, 2.81% predators, 1.58% scrapers, and 0.92% filter-feeders. Spatial distribution patterns of macroinvertebrate communities corresponded with submerged macrophyte distribution. Biomass showed significant seasonal variation (p < 0.05), being higher in autumn and winter than spring and summer, while other community characteristics exhibited no significant seasonal differences. Redundancy analysis identified dissolved oxygen (DO), water depth (WD), pH, permanganate index (CODMn), transparency (SD), and conductivity (Cond) as key environmental drivers. Over two decades, CODMn showed persistent increase while Chl.a concentration rose and SD declined annually post-regime shift. Comparative analysis revealed dominance of scrapers (Gastropoda) during the clear-water state versus gather-collectors (Tubificidae and Chironomidae) in the turbid-water state, with higher species richness, density, biomass, and diversity indices observed during the macrophyte-dominated phase. This study provides critical scientific basis for comprehensive assessment of Caohai Lake"s aquatic ecosystem status, understanding macroinvertebrate responses during plateau lake regime shifts, and implementing targeted ecological restoration measures.
Available online: May 13, 2025
Abstract:
Climate change and the operation of hydraulic projects have significantly altered the water cycle in the Three Gorges Reservoir area. The Three Gorges Reservoir area has experienced recurrent seasonal droughts in recent years. Analyzing the evolution characteristics and driving mechanisms of seasonal agricultural drought in this? region, as well as coupled with the quantitative determination of yield reduction thresholds under current drought defense conditions, is significantly important for developing a systematic response to agricultural droughts. Firstly, the spatiotemporal evolution of seasonal agricultural drought in the reservoir area from 1982 to 2022 was investigated, based on the Standardized Soil Moisture Index (SSMI). Furthermore, additional analyses were conducted using Path Analysis to explore key driving factors. Additionally, drought return periods and representative drought years were determined using Copula theory, and historical typical drought scenarios are extracted. On this basis, effective rainfall was introduced to improve the parameters of the Jensen model, considering losses due to evaporation, interception, and runoff. A new method for calculating the drought-induced crop yield reduction thresholds under historical typical drought scenarios and current defense conditions was proposed based on the improved Jensen model. recurrence of historically typical drought. The results showed that agricultural droughts in the Three Gorges Reservoir area intensified between 1982 and 2022, with significant spatiotemporal variability. Specifically, the tail section of the reservoir was identified as the high-frequency agricultural drought-prone area, while the middle reaches were characterized by long-duration, high-intensity, and severe droughts. Similarly, the upper reaches were prone to extreme, long-duration droughts. Further analysis revealed that future agricultural droughts in the reservoir area were expected to decrease overall. The key driving factor for summer-fall droughts was precipitation, while potential evapotranspiration was the directly influenced factor for winter-spring consecutive droughts. Finally, under the current water conservancy defense conditions, drought-induced crop yield reduction thresholds for return periods of 2, 5, 10, 20, and 50 years were calculated as 1.23%, 5.12%, 8.13%, 15.44%, and 22.32%, respectively. Overall, these findings provided technical support for drought-resilient water resource planning, drought replenishment scheduling, and scenario-based water management in the Three Gorges Reservoir area.
Climate change and the operation of hydraulic projects have significantly altered the water cycle in the Three Gorges Reservoir area. The Three Gorges Reservoir area has experienced recurrent seasonal droughts in recent years. Analyzing the evolution characteristics and driving mechanisms of seasonal agricultural drought in this? region, as well as coupled with the quantitative determination of yield reduction thresholds under current drought defense conditions, is significantly important for developing a systematic response to agricultural droughts. Firstly, the spatiotemporal evolution of seasonal agricultural drought in the reservoir area from 1982 to 2022 was investigated, based on the Standardized Soil Moisture Index (SSMI). Furthermore, additional analyses were conducted using Path Analysis to explore key driving factors. Additionally, drought return periods and representative drought years were determined using Copula theory, and historical typical drought scenarios are extracted. On this basis, effective rainfall was introduced to improve the parameters of the Jensen model, considering losses due to evaporation, interception, and runoff. A new method for calculating the drought-induced crop yield reduction thresholds under historical typical drought scenarios and current defense conditions was proposed based on the improved Jensen model. recurrence of historically typical drought. The results showed that agricultural droughts in the Three Gorges Reservoir area intensified between 1982 and 2022, with significant spatiotemporal variability. Specifically, the tail section of the reservoir was identified as the high-frequency agricultural drought-prone area, while the middle reaches were characterized by long-duration, high-intensity, and severe droughts. Similarly, the upper reaches were prone to extreme, long-duration droughts. Further analysis revealed that future agricultural droughts in the reservoir area were expected to decrease overall. The key driving factor for summer-fall droughts was precipitation, while potential evapotranspiration was the directly influenced factor for winter-spring consecutive droughts. Finally, under the current water conservancy defense conditions, drought-induced crop yield reduction thresholds for return periods of 2, 5, 10, 20, and 50 years were calculated as 1.23%, 5.12%, 8.13%, 15.44%, and 22.32%, respectively. Overall, these findings provided technical support for drought-resilient water resource planning, drought replenishment scheduling, and scenario-based water management in the Three Gorges Reservoir area.
fengning, qinxiwei, mayuliang, pantong, chenjianzhou, dingchengwang, jiangziwen, zhangdong, liuchenglin, liqingkuan, renerfeng, zhangfan
Available online: April 17, 2025
Abstract:
There are abundant brine resources in the Balun Mahai Basin of Qaidam, but the genetic mechanism and potential of brine resources still need to be determined. This study focuses on the intercrystalline brine in the Balema Lake Basin, conducting geochemical research on elements and hydrogen-oxygen isotopes to systematically analyze its water source, solute origins, evolution process, and genesis model. The study also explores the mining potential of potassium, boron, and lithium elements. The results show that the intercrystalline brine in the northern part of the Balema Lake Basin is of the magnesium sulfate subtype, while the southern part predominantly features chloride water. The solutes in the brine mainly originate from the dissolution of halite, potassium salts, and gypsum. The water chemistry is controlled by evaporation, water-rock reactions, and cation exchange. The chloride-type water in the south may be influenced by deep Ca-Cl water flowing along faults. The water chemistry characteristics indicate that the intercrystalline brine is formed by halite dissolution, with low metamorphic degree and poor sealing in the salt-bearing layers. Hydrogen-oxygen isotopes show that the main water source of the intercrystalline brine is atmospheric precipitation or snowmelt from the Qilian Mountains, with the primary recharge sources being the Yuka River and shallow groundwater flowing through the alluvial fan. Strong evaporation and water-rock interactions have significantly impacted the formation of the brine deposits. The differences in water chemistry types and spatial distribution between the northern and southern regions are fundamentally related to the recharge and mixing of these two sources. The brine genesis can be summarized as a "dissolution recharge + deep recharge" dual mining model. The brine in the study area has considerable potential for potassium, boron, and lithium resources. Based on the comprehensive water chemistry characteristics, salt layer thickness, regional salt formation evolution process, drilling sites ZK7618, ZK8014, ZK8024, and ZK8431 are likely favorable targets for mineral exploration.
There are abundant brine resources in the Balun Mahai Basin of Qaidam, but the genetic mechanism and potential of brine resources still need to be determined. This study focuses on the intercrystalline brine in the Balema Lake Basin, conducting geochemical research on elements and hydrogen-oxygen isotopes to systematically analyze its water source, solute origins, evolution process, and genesis model. The study also explores the mining potential of potassium, boron, and lithium elements. The results show that the intercrystalline brine in the northern part of the Balema Lake Basin is of the magnesium sulfate subtype, while the southern part predominantly features chloride water. The solutes in the brine mainly originate from the dissolution of halite, potassium salts, and gypsum. The water chemistry is controlled by evaporation, water-rock reactions, and cation exchange. The chloride-type water in the south may be influenced by deep Ca-Cl water flowing along faults. The water chemistry characteristics indicate that the intercrystalline brine is formed by halite dissolution, with low metamorphic degree and poor sealing in the salt-bearing layers. Hydrogen-oxygen isotopes show that the main water source of the intercrystalline brine is atmospheric precipitation or snowmelt from the Qilian Mountains, with the primary recharge sources being the Yuka River and shallow groundwater flowing through the alluvial fan. Strong evaporation and water-rock interactions have significantly impacted the formation of the brine deposits. The differences in water chemistry types and spatial distribution between the northern and southern regions are fundamentally related to the recharge and mixing of these two sources. The brine genesis can be summarized as a "dissolution recharge + deep recharge" dual mining model. The brine in the study area has considerable potential for potassium, boron, and lithium resources. Based on the comprehensive water chemistry characteristics, salt layer thickness, regional salt formation evolution process, drilling sites ZK7618, ZK8014, ZK8024, and ZK8431 are likely favorable targets for mineral exploration.
Available online: April 17, 2025
Abstract:
The Qaidam basin serves as the primary reservoir of potash salt resources and the key production base for potash fertilizer in China. Recent geological explorations have identified a novel type of potassium-bearing sand and sandstone pore brine deposit in the western foreland alluvial fan of the basin. This newly discovered deposit is believed to contain significant potassium chloride resources, with the brine displaying prominent attributes of high sodium and chlorine levels, and a mineralization model resembling that of "inherited halite rock". Located as a secondary basin and distinct from the Kunteyi basin on the northern margin of Qaidam, the Mahai basin is a small lake basin characterized by various types of brines (intercrystalline brines, confined brines, sand-gravel brines, anticlinal structure brines, etc.). In this study, by conducting a comparative analysis of the major and trace ion content, salinity, and hydrogen and oxygen isotope composition of river water and various brines in the Mahai basin, the following main conclusions have been drawn:① The average K+ content and TDS value of the sand-gravel brines in the Mahai basin are 2.16 g/L and 254.2 g/L, respectively, indicating a notably high ratio of Na++ Cl-/TDS (0.94). These brines belong to the Na-Cl type hydrochemical classification; ② While the potassium K+ content and TDS value of the sand-gravel brines in the Mahai basin are lower than those in the surface brines, intercrystalline brines, and confined brines of Mahai Salt Lake, they are close to the minimum threshold required for industrial potassium salt exploitation, suggesting a certain potential for resource development. The spatial distribution of K+ in sand-gravel brines, intercrystalline brines, and confined brines closely aligns with potassium-containing evaporites. Considering the salinity gradient and gravitational effects influenced by differences in brine TDS and burial depth, it is suggested that the salt solute and potassium in sand-gravel brines originate from the recharge of intercrystalline brines and confined brines; ③ Through the utilization of the K-B-Li equivalent map and analysis of varying B content in different water sources, it is demonstrated that the sand-gravel brines consist of a mixture of Yuqia River water, intercrystalline brines, and confined brines; ④ The δD-δ18O values of the sand-gravel brines in the Mahai basin range from -56.9‰ to -17.6‰ and -5.70‰ to +6.00‰ for hydrogen and oxygen isotopes, respectively. These values exhibit similar characteristics to the confined brines and intercrystalline brines, evenly distributed on both sides of the local evaporation line. Additionally, as the 2H-18O increases, the concentrations of B and Li also increase. These findings indicate that the sand-gravel brines have undergone evaporation and concentration. Consequently, the sand-gravel brines have been inheriting solutes from intercrystalline brines and confined brines over a long period, including ions such as K+, Na+, and Cl-, leading to their similar H-O isotopic signatures.
The Qaidam basin serves as the primary reservoir of potash salt resources and the key production base for potash fertilizer in China. Recent geological explorations have identified a novel type of potassium-bearing sand and sandstone pore brine deposit in the western foreland alluvial fan of the basin. This newly discovered deposit is believed to contain significant potassium chloride resources, with the brine displaying prominent attributes of high sodium and chlorine levels, and a mineralization model resembling that of "inherited halite rock". Located as a secondary basin and distinct from the Kunteyi basin on the northern margin of Qaidam, the Mahai basin is a small lake basin characterized by various types of brines (intercrystalline brines, confined brines, sand-gravel brines, anticlinal structure brines, etc.). In this study, by conducting a comparative analysis of the major and trace ion content, salinity, and hydrogen and oxygen isotope composition of river water and various brines in the Mahai basin, the following main conclusions have been drawn:① The average K+ content and TDS value of the sand-gravel brines in the Mahai basin are 2.16 g/L and 254.2 g/L, respectively, indicating a notably high ratio of Na++ Cl-/TDS (0.94). These brines belong to the Na-Cl type hydrochemical classification; ② While the potassium K+ content and TDS value of the sand-gravel brines in the Mahai basin are lower than those in the surface brines, intercrystalline brines, and confined brines of Mahai Salt Lake, they are close to the minimum threshold required for industrial potassium salt exploitation, suggesting a certain potential for resource development. The spatial distribution of K+ in sand-gravel brines, intercrystalline brines, and confined brines closely aligns with potassium-containing evaporites. Considering the salinity gradient and gravitational effects influenced by differences in brine TDS and burial depth, it is suggested that the salt solute and potassium in sand-gravel brines originate from the recharge of intercrystalline brines and confined brines; ③ Through the utilization of the K-B-Li equivalent map and analysis of varying B content in different water sources, it is demonstrated that the sand-gravel brines consist of a mixture of Yuqia River water, intercrystalline brines, and confined brines; ④ The δD-δ18O values of the sand-gravel brines in the Mahai basin range from -56.9‰ to -17.6‰ and -5.70‰ to +6.00‰ for hydrogen and oxygen isotopes, respectively. These values exhibit similar characteristics to the confined brines and intercrystalline brines, evenly distributed on both sides of the local evaporation line. Additionally, as the 2H-18O increases, the concentrations of B and Li also increase. These findings indicate that the sand-gravel brines have undergone evaporation and concentration. Consequently, the sand-gravel brines have been inheriting solutes from intercrystalline brines and confined brines over a long period, including ions such as K+, Na+, and Cl-, leading to their similar H-O isotopic signatures.
