Abstract:Sturgeons have lived on the earth for hundreds of millions of years with little morphological changes, thus called as “living fossils”. They are one of the most endangered fish groups. Among the three sturgeon species in the Yangtze River, Psephurus gladius has extincted functionally, Acipenser sinensis is going to become extinct in natural environments, and Acipenser dabryanus is also critically endangered. The negative effects of spawning behaviors caused by the construction of dams in the main river is the biggest reason, followed by overfishing. There are serious misjudgments in authoritative experts about the impacts of dam construction on sturgeons, and the measures taken to save the fish after the completion of the dam have little effect, as the paddlefish has long gone, and the wild population of Chinese sturgeon is on the verge of extinction. In recent years, there is a popular viewpoint that the release of warm water from the reservoir delayed the spawning of Chinese sturgeon, consequently with their failure to lay any egg. However, postponement doesn't lead to the conclusion that it's impossible to lay eggs. Accordingly, the proposed joint reservoir operation is not effective even if it can be implemented. As the giant and long-lived Chinese sturgeons have low ecological resilience, and need to cross a vast space between coastal waters and the upper Yangtze River to complete the life story, if they can't lay eggs naturally, their extinction will happen sooner or later. During the past decades, millions of Chinese sturgeons were released artificially into the Yangtze River, but few survived with little supplement to the wild population. Therefore, it is urgent to re-evaluate the endangered mechanisms (especially the ruined conditions for natural reproduction) and the effects of artificial release and to re-adjust fish rescue strategies.

Abstract:The effect of Gezhouba Dam on the gonadal development of the Chinese sturgeon (Acipenser sinensis Gray, 1835) has been a controversial issue, and how strong its impact is directly related to the population survival of the Chinese sturgeon. Using our migration dynamics model and gonadal development model, we reveal the population structure traits, spatiotemporal distribution and gonadal development process of Chinese sturgeon in the Yangtze River, and the impacts of Gezhouba Dam. Through the analysis and evaluation of the relevant literatures, we believed that Ke Fuen et al (1985) of the Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, carried out a solid research on the gonadal degeneration of the Chinese sturgeon caused by the Gezhouba Dam; their finding was reliable that the serious gonadal degeneration would resulted in a quite limited breeding size and then the severe decline of the population size after several years. This conclusion has been proved by the fact that the Chinese sturgeon population has been declining continuously since the 1990s. In contrast, as a professional supporter for fish rescue programme of Gezhouba Dam, the Institute of Hydrobiology, Chinese Academy of Sciences, has offered inadequate and unreliable findings at that time, denying the serious gonadal degeneration of Chinese sturgeon. Using our models' findings to re-analyze the historical survey data, we presented other evidences of severe gonadal degeneration of the Chinese sturgeon. Our results show that the blocking effect of Gezhouba Dam led to the gonadal degeneration rate of about 75%, which has been neglected or belittled since the implementation of the fish rescue programme of Gezhouba Dam. This has had a serious effect on the protection of Chinese sturgeon.

Abstract:The wild Chinese sturgeon (Acipenser sinensis Gray, 1835) has been facing the risk of extinction due to no consensus on the chief culprit of its survival crisis for a long time, resulting in the absence of targeted protection measures. Based on our population model of Chinese sturgeon, we merged the five potential culprits proposed by the elite experts—illegal fishing, pollution, shipping, global climate change and Yangtze dams—to the four possible factors of Chinese sturgeon population decline, which are breeding population loss, recruit population loss, reducing survival rate, and cumulative effects of the Yangtze dams. Then we calculated single-factor and multi-factor scenarios of anthropogenic activities and evaluated the possibility of these scenarios. The results show that the cumulative impact of the Yangtze dams is the main cause of the survival crisis of Chinese sturgeon. Other factors such as fishing, pollution, and shipping have a certain adverse effect on the population. Our quantitative scenario calculation and analysis validated the consensus that the Chinese sturgeon was listed as the sole target for the fish rescue programme of Gezhouba Dam (GD) in 1982 because of the worst impact of the GD on the Chinese sturgeon. We reveal the impact mechanism of the Yangtze dams on the decline and even extinction and overturn the long-standing mainstream opinions that the survival crisis of Chinese sturgeon was caused by illegal fishing, pollution, shipping, or global climate change. Then we suggest that targeted measures must be adopted to mitigate the impact of the Yangtze dams to save wild Chinese sturgeon and restoring the natural reproduction of wild population is now the urgent matter for the Chinese sturgeon conservation.

Abstract:To explore the pollution sources and contribution rate of urban eutrophication lakes, a typical eutrophic lake (Lake Houguanhu in Wuhan) in the Yangtze River Basin was selected for research. With the field-measurement method, the mean-concentration method and the pollution-discharge-coefficient method, the external pollutant sources (including point source and non-point source) of Lake Houguanhu was analyzed. Non-point sources (NPS) were further divided into several source types, such as the pollutants from the rural life, the agricultural planting, the aquaculture, the livestock, the poultry farming and the urban runoff. Results show that the COD in Lake Houguanhu is mainly from the point source with a contribution rate of 54%, total phosphorus is mainly from the non-point sources with a rate of 71%. Further exploring the main non-point sources, it is found that the total phosphorus is mainly from the agricultural planting and aquaculture, with the contribution rates of 41% and 30%, respectively. The largest contribution of COD, ammonia nitrogen and total nitrogen in NPS is urban runoff, with contribution rates of 61%, 53% and 37%, respectively. For administrative districts, the highest contribution rates of COD, ammonia nitrogen, total nitrogen and total phosphorus emissions are Zhuankou Street Office (25.24%), Caidian Street Office (23.28%), Yongfeng Street Office (24.04%) and Daji Street Office (26.15%). Results indicated that, with point source treatment of the Zhuankou Street and the Yongfeng Street, the COD and ammonia nitrogen loads can be effectively reduced. The agricultural non-point source pollution prevention and control of Daji Street is the focus of total phosphorus management in Lake Houguanhu Basin.

Abstract:Twenty-five water sampling sites in Lake Baiyangdian were selected to investigate the characteristics of water quality in January 2019, including primitive area, tourist rea, living area, aquaculture area and enter area. Temperature, dissolved oxygen (DO), ammonia nitrogen (NH₃-N), nitrous oxide nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N), total nitrogen (TN), total phosphorus (TP), permanganate index were used as factors to evaluate water quality based on the single factor evaluation method, comprehensive pollution index (K) method and principal component analysis method, respectively. The results indicated that temperature of the lake had a minor fluctuation, the DO exhibited a huge variation, TN and TP presented high concentrations during the freezing period in Lake Baiyangdian. The single factor evaluation showed that when TN was used for evaluation, Class Ⅲ water bodies accounted for 28%, and the rest were Class Ⅳ, Class Ⅴ and lower Ⅴ among the 25 sampling points. When TP was used, Class Ⅲ water bodies accounted for 16%, and the rest were IV, Class V and lower V. Overall, the quality of Lake Baiyangdian water was relatively poor. The comprehensive pollution index method showed that water quality in the living area was better, while the enter area was worse. The water quality of Baigou River, Fuhe River and Puhe River were the worst among all sampling sites, which belonged to heavy pollution rivers involved to TN and TP. The principal component analysis indicated that the six rivers of the sedimentation area had large deviations in water quality and pollution influencing factors. TN and TP were highly correlated with PCA1 and PCA2 in the physical and chemical indicators. Overall, the evaluation combined qualitative and quantitative methods showed that the TN and TP were the main limiting factor in freezing period of Lake Baiyangdian. From all the results, the freezing period is important for lake water bodies, probing the source of pollution and controlling it can significantly improve the water quality of the lake. The series of researches not only offers the best opportunity for the treatment of water, but also provides guidance for the treatment and restoration of water pollution in Lake Baiyangdian.

Abstract:In order to identify the source of heavy metals and quantify their contributions, surface sediment of Lake Poyang during the wet season were selected as the research object, and the contents of 14 heavy metals (V, Cr, Co, Ni, Cu, Zn, Sr, Mo, Cd, Sb, W, Pb, Hg and As) were determined. The pollution and spatial distribution characteristics of 14 heavy metals were analyzed, and the principal component analysis (PCA) and positive definite matrix factorization (PMF) were applied to apportion the sources of sediment heavy metals. The results showed that except for V and Cr, the average contents of Cd, Mo, Hg, Cu, Pb, Zn, W, Sr, As, Ni, Co and Sb were 5.7, 2.2, 1.9, 1.8, 1.5, 1.5, 1.4, 1.3, 1.3, 1.2, 1.0 and 1.0 times of their respective soil background values of Jiangxi Province. The exceeding rates of Cd, Hg, Cu, Mo, Pb, Sr and Zn were relatively high, there were 100%, 100%, 100%, 100%, 97%, 97% and 93% of sediment samples with higher Cd, Hg, Cu, Mo, Pb, Sr and Zn contents than their respective soil background values of Jiangxi Province, respectively. And 51% of sediment samples had higher Cd contents than the risk screening values for soil contamination of agricultural land. V, Cr, Co, Ni, Cu, Zn, Sr, Mo, Sb, W, Pb, Hg and As were at unpolluted to minimal contamination levels, while Cd displayed moderate contamination level, closed to heavy contamination level. Overall, the pollution of Cd was relatively serious. The distribution of heavy metals had significant regional characteristics. The spatial distributions of Cr, Cu, Zn, Sr, Pb, Hg and As were very similar, showing the high content values were clustered near the river inlets of Ganjiang, Fuhe, Xinjiang, Raohe, while Co, Ni, Mo and Sb were obviously concentrated in the southern of lake region, the northeast region and the Xiushui into the lake. The spatial variability of Cd and W was relatively large, while the contents of V were relatively uniform. Source apportionment results of PCA and PMF indicated that the heavy metals in surface sediments from Lake Poyang during the wet season were affected by four sources. Mining and industrial activities, tailings and waste residue, agricultural activities were identified as the main anthropogenic sources for sediment heavy metals in this study area, accounting for 38%, 28% and 19% of the total contribution, respectively. The remainder was the natural source, accounting for 14% of total contribution.

Abstract:It is of great significance to strengthen the study on the assessment and driving mechanism of landscape ecological vulnerability in the ecological core area of the watershed for the optimization and regulation of ecosystem functions. Based on the grid unit scale, using spatial data exploration and geographical weighted regression (GWR) and other tools, the temporal and spatial evolution characteristics and driving mechanism of landscape ecological vulnerability in Chaohu Basin during 1970-2015 were analyzed. The results show that: from 1970 to 2015, the land landscape types of water environment protection zone in Chaohu Basin show a trend of “two falls and three rises”, among which, the agricultural land landscape decreased by 6.62%, and the construction land landscape increased by 6.26%. In the past 45 years, the average value of landscape ecological vulnerability decreased from 2.9347 in 1970 to 2.6720 in 2000, and increased to 2.7989 in 2015, showing a fluctuating downward trend as a whole. The spatial distribution of apparent ecological vulnerability has a significant clustering feature. GWR regression coefficient shows that the driving forces of each driving factor on the ecological vulnerability of the landscape in the study area are different, in order: agricultural land fragmentation (FN) > normalized differential vegetation index (NDVI) > slope (SLOP) > land use degree index (LUI), and the regression coefficient of each factor has spatial non-stationary. Among them, the regression coefficient of FN factor shows a trend of gradually increasing from west to east, the spatial distribution of the regression coefficient of NDVI factor shows a trend of decreasing from the middle to both sides, the regression coefficient of SLOP factor shows a trend of decreasing from west to east, the regression coefficient of LUI factor shows a trend of gradually decreasing from east, south to northwest. The spatial distribution characteristics of the regression coefficients show that the effects of different factors on the ecological vulnerability of landscape are anisotropic. The results can provide decision support for practice of ecological restoration and landscape pattern optimization of water environment protection area in Chaohu Basin.

Abstract:The nitrogen and oxygen isotopic composition and hydrochemical characteristics of water were studied systematically to determine the main sources of nitrate in Lake Caohai and its rivers, and the contributions of each source were quantitatively analyzed. The ratio of NO₃^-/Cl^- to Cl^- in the lake water showed that the lake was mainly affected by livestock manure and urban sewage in wet season, while the ratio in rivers and wells indicated that rivers were affected by agricultural activities and urban sewage. The analysis of δD-water and δ¹⁸O-water showed that atmospheric precipitation was the main source of water in Lake Caohai and its rivers, with a strong evaporation. The value of δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^- in lake water were -5.56‰-11.30‰ and 0.02‰-25.40‰ respectively, which were more negative than the rivers and more positive than the wells. The results of SIAR model showed that nitrate in Lake Caohai and its rivers mainly came from agricultural activities related to fertilizer, soil organic N and livestock manure, and its contributions was more than 60%. The contribution rate of urban sewage was about 25%. The contribution of atmospheric precipitation was mainly reflected in the lake water.

Abstract:Restoration of submerged macrophytes is a key step in the reconstruction of eutrophic lake ecosystem. The growth of submerged macrophytes is influenced by many factors. The effects of silicate mineral maifanite supplement on the physiological and ecological process of Vallisneria spiralis was investigated in this study, for providing a technical reference for the further application in aquatic ecological restoration. The results showed that maifanite could significantly promote the growth of V. spiralis. The biomass, height, leaf numbers, root length of V. spiralis in the maifanite-supplemented group were better than those of the control. Moreover, the modified maifanite group performed better than the raw maifanite group. The photosynthetic pigment, root activity and peroxidase (POD) activity of V. spiralis in 1 cm maifanite-treated group were better than those of the control to some extent during the vigorous period of plant growth, and the content of malondialdehyde (MDA) is lower than the control group. It was found that maifanite contained abundant constant and trace elements, which are required for the growth of V. spiralis. It is concluded that maifanite is beneficial to the growth of V. spiralis and can be further applied to ecological restoration of eutrophic lakes.

Abstract:In this study, water samples were taken from 34 sampling points in the main stream and tributaries of the Ganjiang River in January and July 2015, and the water quality indicators such as electrical conductivity (EC), water chemical ions and the concentrations of inorganic nitrogen were determined. The land use structure in the Ganjiang River Basin was represented by landscape type ratios, and the landscape pattern was represented by landscape indexes, based on the 30 m resolution land use data. The Pearson correlation analysis, Bioenv analysis, Mantle test and variation partitioning analysis (VPA) were used to analyze the impacts of watershed land use structure and landscape pattern on the water quality of the Ganjiang River. The results showed that: (1) The concentrations of Cl^- and Na⁺ were the highest in the upstream, EC, concentrations of Cl^-, Na⁺, K⁺ and Ca²⁺ were the lowest in the middle stream, and EC, concentrations of HCO₃^-, SO₄^2-, Mg²⁺, Ca²⁺ and NO₃^--N were the highest in the downstream. (2) The construction land was the individual land use type that best explained the variations in water quality. Forest land, paddy fields and construction land were the subset of land use types that best explained the variations in water quality. (3) The ENN_MN index was the individual landscape index that best explained the variations in water quality. NP, COHES and ENN_MN were the subset of landscape index that best explained the variations in water quality. (4) In the dry season, the land use structure and landscape pattern accounted for 41.1% and 17.2% of the variance in water quality, respectively; the effect of landscape pattern was totally interacted with land use structure, without an independent contribution. In the wet season, the land use structure and landscape pattern accounted for 51% and 53% of the variance in water quality, respectively; the interactive part was 37%. Both land use structure and the landscape pattern have a great influence on water quality of Ganjiang River, and their interactive parts play an important role in this influence. The influence of landscape pattern on water quality in dry season was included in the interaction with land use structure.

Abstract:Rivers are considered to be an important source of atmospheric CO₂, while the responses of riverine CO₂ evasion rate to intensified human activities such as urbanization are poorly understood. The characterization of CO₂ partial pressure (pCO₂) in three rivers with different urbanization gradients of the Three Gorges Reservoir area was studied. Water sampling was thus carried out in August 2018. pH values and water temperatures were measured in situ using a portable CyberScan PCD 650 multi-parameters system (Eutech, USA), while both the dissolved organic carbon (DOC) and nutrients (DTN-dissolved total nitrogen, DTP-dissolved total phosphorus) were determined in the laboratory. Land use composition was extracted by ArcGIS 10.3. The pCO₂ of rivers with different urbanization intensity was calculated by pH, alkalinity and water temperature. Our results indicated that the proportions of urban area are as follows: Ruxi RiverpCO₂ were 1790±1210 μatm, 2006±3546 μatm, 4094±4218 μatm respectively. The average pCO₂ were much higher than the atmospheric equilibrium,and the studied rivers were therefore characterized as a CO₂ source. The concentrations of DOC, DTN and Alk (Alkalinity), EC (Conductivity) were significantly different among rivers. The concentrations of DOC, DTN, DTP and Alk were consistent with the riverine urbanization gradients. We concluded that urbanization could enhance riverine pCO₂, and thus potentially increased riverine CO₂ evasion. Our results supported the hypothesis that human intensive practices would increase riverine dissolved CO₂ and water-air areal flux, which would be helpful for the prediction of riverine CO₂ emission under regional and global urbanization.

Abstract:Dissolved organic matter (DOM) is ubiquitous in environmental waters. It has a characteristic of continuous molecular weight distribution and can significantly affect the migration, transformation, and fate of pollutants in natural waters. Water samples of Lake Poyang were collected in the spring of 2019, and DOM samples were divided into low molecular weight (LMW, <1 kDa) and high molecular weight (HMW, 1 kDa-0.45 μm) components through ultrafiltration. Fluorescence parallel factor (PARAFAC) analysis and ICP-MS were used to analyze the spectral and metal properties in different molecular weight solutions. Results showed that 43%-55% of Lake Poyang's DOC was LMW, and 45%-57% HMW. DOM fluorescence samples were identified as two fulvic-like components (C1, C2) and a humic-like component C3, of which 60%-73% of C1 was distributed in LMW, 77%-93% of C2 distributed in HMW, and C3 almost evenly distributed in the LMW- and HMW-DOM, which may be related to the traditional fluorescent peak contained in each fluorescent components. Calculation of fluorescence index (FIX, <1.4) and biological index (BIX, <0.8) indicates that the DOM of Lake Poyang's terrestrial source characteristics were significant, and the HMW-DOM had higher terrigenous characteristics and aromaticity than the LMW-DOM. Heavy metal Cr, Mn, Fe, and Pb were mainly distributed in HMW (63%-94%), As, Cd, Ba, Se, and Sb were mainly distributed in LMW (63%-84%), and Cu, Zn, Ni, and Co were almost evenly distributed in LMW- and HMW-DOM. Most metals had negative correlations with C2 percentage and positive correlation with C3 percentage, indicating that the complexation of heavy metal ions with DOM in water may be mainly through humic-like component C3. The distribution of heavy metal content was greatly affected by HMW-DOM, indicating the important role of anthropogenic activities in Lake Poyang's heavy metal distribution.

Abstract:Adsorptive fractionation of macrophyte- and algae-derived dissolved organic matter (MDOM and ADOM) on goethite was investigated to demonstrate the transfer of autochthonous DOM at the water-sediment interface in eutrophic lakes. Excitation emission matrix spectra with parallel factor analysis showed that protein-like substances, including tyrosine- and tryptophan-like component (C2 and C3), accounted for 70% and 93% of total fluorescent components in MDOM and ADOM, respectively. While, contents of humic acid- and fulvic acid-like components (C4 and C1) were limited in both DOMs. The two DOMs were effectively adsorbed on goethite and this adsorption process can be well simulated by pseudo-first order kinetic equation. Fitting by adsorption isotherm revealed the stronger, more nonlinear adsorption of ADOM (23.77 mg/g of Q_max) on goethite than MDOM (19.10 mg/g of Q_max). Specifically, a nonlinear adsorption was found between protein-like substances and goethite, whereas the adsorption of humic-like substances was almost linear. The adsorption capacity of DOM components to goethite followed the order of: C3 > C2 > C4 > C1, which was dependent on their initial content, molecular weights, aromaticity, and binding sites. Infrared spectroscopy further indicated that amino, carboxyl, and hydroxyl were responsible functional groups for the heterogeneous adsorption. Overall, the production of ADOM and MDOM significantly changes the organic compositions on goethite surface and affects the biogeochemical cycles in lake sediments.

Abstract:Eutrophication has become a major water environmental problem all over the world, and cyanobacterial blooms are one of the most common phenomena in eutrophic lakes. Thereafter, a large amount of cyanobacterial detritus will be produced after the blooms, and the effects of these detritus on water quality and biological communities are poorly studied. A 28-day mesocosm experiment was conducted in Meiliang Bay of Lake Taihu to study the effects of cyanobacterial detritus on nutrients dynamics and the biomass of aquatic organisms. We found that the concentration of nutrients increased rapidly after addition of Microcystis detritus, with the maximum mean concentration of total nitrogen (TN) and total phosphorus (TP) up to 3.86 mg/L and 0.36 mg/L, respectively. Meanwhile, phytoplankton biomass (Chl.a) increased dramatically, after detritus addition, in the first nine days, then it gradually declined to the end of the experiment. In addition, the biomass of periphyton decreased gradually after cyanobacterial detritus addition which may be mainly due to the decreasing water transparency caused by the rapid increase of Chl.a limiting the growth of periphyton. Meanwhile, the biomass of Limnodrilus spp. increased gradually, and peaked on day 20, indicating that cyanobacterial detritus facilitates the population development of Limnodrilus spp. Our results have implications for eutrophic lake management and better understanding the effects of cyanobacterial blooms on aquatic ecosystems.

Abstract:In reservoir ecosystems, both macroinvertebrates and plankton play an important role in the matter cycling by interactions in food webs. Nanwan Reservoir and Tangpu Reservoir are deep reservoirs with eutrophication and long-term thermal stratification. In this study, these two reservoirs for drinking water supply were investigated to compare their trophic status, macroinvertebrate community structure, stranding crops and biodiversity. The macroinvertebrate communities were quantitatively assessed by Integral index of communities state (IICS) index, and the relationship between the density of plankton and IICS was explored by a PLS model, Spearman rank correlation and regression charts. The results showed that the trophic state index of Nanwan Reservoir was higher than that of Tangpu Reservoir, oligochaetes dominated in Nanwan Reservoir while chironomids did in Tangpu Reservoir. The collectors dominated in Nanwan Reservoir, where their proportion was much higher than Tangpu Reservoir. In deep reservoirs with thermal stratification, eutrophication aggravated the anoxic or anaerobic status at the reservoir bottom, resulting in the periodic anoxic disturbance to macroinvertebrates and reduced standing crops and biodiversity. The relationship between plankton and macroinvertebrate community shifting from positive correlation to negative one was related to the aggravation of reservoir eutrophication. The deterioration of the benthic habitat environment caused by the intensification of eutrophication and the food shortage caused by plankton's avoidance of unfavorable environment were the fundamental reasons for the sustained decline of macroinvertebrate population. Therefore, the reservoir eutrophication can be detected by exploring the relationship between macroinvertebrate and plankton community, for the aim of providing more valuable reference information to reservoir management.

Abstract:Dolichospermum is a filamentous cyanobacterial genus with the potential capacity to produce multi-cyanotoxins and taste and odour (T/O) compounds. Twenty-four strains of Dolichospermum isolated from Lake Zhelin, Jiangxi were morphologically and molecularly characterized for exploring the biological properties of Dolichospermum species. They were classified into four species as D. planctonicum, D. affine, D. circinale and D. spiroides. Phylogenetic analysis based on the 16S rRNA sequences showed that all Dolichospermum strains here were highly similar to the strains isolated from Japan and other regions, but only D. affine was well grouped into one cluster. Based on the secondary structures of 16S-23S ITS, all the Dolichospermum strains showed to have the same structures in D1-D1' region. In Box-B and V3 regions, the structures of D. planctonicum and D. affine were different from those of D. circinale and D. spiroides, indicating the significant difference between two morphological types (coiled and straight type). Based on the DNA molecular detection, the 24 strains of Dolichospermum were not cyanotoxin producers, but four strains of D. planctonicum and one strain of D. circinale showed to contain geosmin synthase gene. Such results not only presented the basic scientific information on biodiversity of bloom forming cyanobacteria and their ecological risk in Lake Zhelin, but also provided the basis on aquatic ecosystematic studies and protection along Lake Poyang watershed.

Abstract:Alpine lakes are sensitive reference systems of global climatic change and other human impacts. As a unique alpine lake, Lake Changhai of Jiuzhaigou National Nature Reserve has important significance in studying its phytoplankton community structure and it's relationship with the environment. It is also important to assess the status of water quality and its influencing factors. In order to understand the phytoplankton community structure, 12 sites were selected to collect phytoplankton samples in July 2014. Vertical stratified sampling was performed at the central sampling point. The 63 taxa of phytoplankton belonging to 38 genera in 6 phyla were identified, the average phytoplankton abundance was 6.98×10⁵ cells/L, the average phytoplankton biomass was 0.31 mg/L. There is no significant difference in the horizontal distribution of the phytoplankton. In the vertical distribution, the abundance of phytoplankton increased first and then decreased from 0.5 m to 50 m, and reached the maximum at the depth of 20 m. Cyclotella changhai and Ceratium hirundinella were the dominant species. Cyclotella changhai were higher amounts, Ceratium hirundinella were higher biomass. The phytoplankton diversity index was low. Synthesizing all kinds of methods to evaluate water quality, Lake Changhai was in a poor-medium pollution state.

Abstract:Submerged plants play an important role in improving eutrophic water and rebuilding aquatic ecosystem. Using remote sensing technology, the distribution and growth of submerged plants can be monitored in real time and in large area. The depth from the water surface to the plant canopy (WDC) directly affects the accurate remote sensing interpretation of submerged plants in lakes and rivers. Based on the measured spectral data, the spectral characteristics of submerged aquatic vegetation in Lake Ulansuhai were analyzed, and the effects of canopy water depth on the reflectance spectra of submerged plants in Lake Ulansuhai were studied. The retrieval model of canopy water depth of submerged plants in Lake Ulansuhai was established. The results showed that 1) There is a reflection peak near the 1662 nm and 2223 nm of the short wave infrared of the emergent plants, which is an important band that distinguishes the emergent plants from the submerged plants and the floating algae. The spectral reflectance of the submerged plants (WDC=0) and the floating algae is very close, but there are obvious differences in the green band (550-690 nm). Therefore, the spectral characteristics of the green band and the short wave infrared band can be used to distinguish emergent plants, submerged plants and floating algae. 2) The spectral reflectance of submerged plant community decreased with the increase of WDC, and it changed most obviously in the range of 700-900 nm, and there was a significant negative correlation between the spectral reflectance of submerged plant community and WDC near the range of 700-735 nm. 3) A single band / band ratio retrieval model of WDC is established, in which the band ratio retrieval model is better than the single band retrieval model. The R² of the band retrieval model is more than 0.70, the RMSE<13.70 cm, the MRPE<28%, and the retrieval accuracy is high, which is suitable for retrieval of canopy water depth of submerged plants of 10-60 cm. 4) The situ spectral reflectance is integrated into the Landsat-8 OLI band by using the spectral response function, and the retrieval model of the water depth of OLI is established. Among them, the power function model of band ratio has the best retrieval effect, the R² is 0.49, the RMSE is 18.17 cm, the MRPE is 40.05%, which can be used for the retrieval of the water depth of the submerged plant canopy in Lake Ulansuhai after accurate atmospheric correction.

Abstract:In order to explore the current situation of the larvae and juvenile fish resources of the four major Chinese carps in Anqing section of the Yangtze River and the relationship between abundance and hydrological factors,a total of 3178 larvae and juveniles were collected during the investigation from April to August of 2016-2018. Among which, Hypophthalmichthys molitrix and Ctenopharyngodon idellus formed the majority, accounting for 67.97% and 23.03% of the total larvae catches respectively. We estimated there were 21.70×10⁸, 14.62×10⁸ and 12.05×10⁸ individual larvae of the four major Chinese carps drifted through the Anqing section in three years, the results indicated a decreasing trend annually. The abundance of Chinese carps has been increased intermittently since mid-April, and peaked in mid-July. The Kruskal-Wallis test showed that, there were significant differences for larvae with the highest drift density in the north of river and the lowest in the middle of the river. According to the results of generalized additive model, the hydrological factors that have significant influence on the abundance of larvae are water temperature, transparency, daily increasing rate of water level and discharge. The orders of the contribution to abundance of larvae were in sequence of the daily increasing rate of water level, transparency, water temperature and the daily increasing rate of discharge. Among them, the abundance of larvae was negatively correlated with the transparency, and positively correlated with the water temperature (24.0-27.3℃), daily increasing rate of water level and discharge. The accumulation of deviance explained by the optimized GAM to the abundance of larvae was 69.8%, which revealed the influence of hydrological conditions on the abundance of Chinese carps resources in early stage at a high degree. The results will provide a scientific basis for the prediction of seedling flood and protection strategy of the four major Chinese carps fisheries resource in the lower reaches of Yangtze River.

Abstract:Urban river-lake connections in different hydrological characteristics waters result in a diverse aquatic environment, which provides heterogeneous habitat conditions and contributes to increase zooplankton diversity. To understand the effects of connectivity and heterogeneity on the rotifer community structure of Lake Liuye and its adjacent waters in Changde city of Hunan, we conducted the survey quarterly on the rotifer community structure and environmental characteristics at 15 sampling sites in Lake Liuye, Chuanzi River and the Changde section of the Yuan River in 2018. During our investigation, the trophic status in different waters decreased in the order: Chuanzi River > Lake Liuye > Yuan River. The Chuanzi River and Lake Liuye were eutrophic, and the Yuan River was mesotrophic. A total of 88 rotifer species (including 8 subspecies and 1 varietas) were recorded. Polyarthra dolichoptera was the dominant species in this system. The highest abundance of rotifers reached 2535 ind./L, and the spatial distribution of annual average abundance decreased in the order: Lake Liuye > Chuanzi River > Yuan River. The temporal distribution of abundance decreased in the order: June > September > March > December. The composition of rotifer species was similar among the three waters with the same first dominant species, while the annual average abundance and diversity indices varied according to spatial heterogeneity. Canonical correspondence analysis indicated that water temperature was the key factor to the variation of rotifer community structure.

Abstract:The upper reaches of the Hanjiang River are the source-water area of the Danjiangkou Reservoir. Its ecological status plays an important role in ensuring the ecological security of the Hanjiang River Basin and the South-to-North Water Transfer Project. In November 2017 and April 2018, we conducted a systematic survey in the upper reaches of the Hanjiang River and its five typical tributaries, in order to find out the characteristics of benthic macroinvertebrate communities in the upper reaches of the Hanjiang River and the typical tributaries of the southern slope of the Qinling Mountains, and to evaluate their bioassessment of water quality. Altogether 240 species of macroinvertebrates were collected, including 209 species of aquatic insects, 13 species of mollusks, 9 species of annelids and 9 species of other groups. Among them, Baetis sp. was the dominant species in all rivers. In addition, other species included Paraleptophlebia sp., Caenis sp., Heptagenia sp., Baetiella sp., Orthocladius sp., Hydropsyche sp., Ephemera sp., Cincticostella sp., Epeorus sp., Sympotthastia sp. and Eukiefferiella sp. From the density of various groups, aquatic insects had an absolute advantage in the Hanjiang River and its five tributaries, accounting for 90.8%-98.9% of the total density. In terms of biomass, in addition to the absolute advantage of mollusks in the main stream of the Hanjiang River, aquatic insects had an absolute advantage in each tributary, accounting for 47.0%-98.9% of the total biomass. In terms of the density of functional feeding groups, direct collectors were the main functional feeding groups in the Hanjiang River and its tributaries, while there were differences in terms of biomass. The predators were the main functional feeding groups in the Jinshui River and the Xun River. The scrapers were the main functional feeding group of the Hanjiang River and the Yue River. The collector-gatherers were the main functional feeding group in the Jinqian River. The collector-filterers were the main functional feeding group in the Xushui River. The redundancy analysis results showed that velocity, total phosphorus and conductivity were the key environmental factors affecting the distribution of benthic macroinvertebrate in the Hanjiang River and its tributaries. The bioassessment of water quality was carried out by using the biotic index (BI) and the Shannon-Wiener index. The evaluation results showed that a few stream sections of the Hanjiang River, the downstream of the Xushui River, the downstream of the Yue River and the mid-lower reaches of the Xun River were slightly to moderately polluted, the other stream sites were in a clean state. The research results can provide basis for ecological management and scientific protection in the upper reaches of the Hanjiang River.

Abstract:In recent years, the large-scale stock enhancement of silver carp, Hypophthalmichthys molitrix had been implemented in the lower reaches of the Yangtze River. It was urgent to study how much resource contribution the stock enhancement of silver carp produced. This study assessed resource contribution rate of stock enhancement of silver carp in Jiangsu section of the Yangtze River from the year 2016-2017, using microsatellite parentage testing technique. Before releasing fries, brood stocks of eight hatcheries, used for breeding, were marked with eleven pairs of ever developed microsatellite primers. These eight hatcheries also were the major institutions that supplied silver carp fries to the releasing work of governments around Jiangsu Province. The results showed that 191 types of alleles were detected between 621 brood stocks hatcheries and 475 captured silver carp in the Yangtze River. The number of different alleles (N_A), the observed heterozygosity (Ho) and the expected heterozygosity (He) were 9-36, 0.536-0.793, 0.597-0.941, respectively, and their corresponding mean values were 17.36, 0.656 and 0.794. All of eleven microsatellite loci were high polymorphism, and the polymorphic information content (PIC) per locus ranged from 0.560 to 0.938 with the mean value of 0.771, which proved 11 pairs of microsatellite primers as an effective tool for parentage identification. Result of parentage testing showed that the non-exclusion probability (NEP) was from 2.4% to 42.4% at the case of parent's unknown gender, and the combined non-exclusion probability (CEP) was over 99.99%. Thirty-nine individuals from 475 silver carps of the Yangtze River were identified as the hatchery-reared offspring, i.e., the recapture rate 8.21%. Through comprehensive analysis, it was concluded that stock enhancement had produced a good supplement effect on silver carp resource from 2016 to 2017.

Abstract:Baige landslide occurred in the upstream of Jinsha River in October 10, 2018 caused the most serious river blockage event in the recent hundred years. Formation and breaking of the Baige landslide-dammed lake (BLDL) had unknown effects on water and sediment conditions and the operation of cascade hydropower stations in the main stream of the downstream Jinsha River. Based on the observational data of the temporary gauge station near the BLDL and the controlled hydrological stations in the main trunk of Jinsha River, the effects of BLDL on water and sediment conditions in the middle and lower Jinsha River are studied. Combining with the operation of cascade reservoirs before and after the breaking of the landslide-dammed lake, the sediment retention amount of cascade reservoirs is estimated. The results showed the breaking of the BLDL formed a super-historical hydrograph of water and sediment in the middle Jinsha River. After the emergency regulation of cascade reservoirs in the middle Jinsha River, the extraordinary flood caused by the outbreak of the BLDL was reduced to a normal flood. Nearly 26% of the sediment generated by landslides is transported and deposited in cascade reservoirs in the middle Jinsha River. Among them, the Liyuan, Ahai, and Jinanqiao hydropower stations intercepted about 14 million tons of sediment, while Longkaikou, Ludila, and Guanyinyan hydropower stations intercepted about 0.43 million tons of sediment. About 74% of the landslide-induced sediment remains near the Baige barrier. Given that all the sediments generated by the Baige landslide are transported into the cascade reservoirs along the middle Jinsha River, the effective reservoir capacity of Liyuan hydropower station will probably not meet the requirement of the reservoir regulating capacity.

Abstract:In this study, the wind-wave model SWAN was used to simulate the characteristics of variations and distributions of wind waves in Lake Chaohu for the year 2018. The model was calibrated and evaluated using observational data. Results suggest that the annual mean significant wave height and wave period of Lake Chaohu during 2018 were 0.16 m and 1.26 s, respectively. The wind wave was strong in spring and weak in autumn. The monthly mean values exhibit great variations. The largest monthly values of 0.22 m and 1.36 s were obtained in April, while these values were 0.11 m and 1.06 s in November, which were the lowest during 2018 and whose variation ranges were 52% and 22% of the maximum values, respectively. Among different lake basins, monthly mean wave height in the east basin and central basin were the highest, followed by the west basin. The highest value of monthly maximum significant wave height and wave period appeared in the east basin or the central basin. The values of monthly maximum significant wave height and wave period varied significantly during different months, whose variation ranges were 61% and 27% of the maximum values, respectively. The distribution ratio of the high values of monthly significant wave height and wave period computed by model in different lake zones were large in the east basin or central basin, but it was small in the west basin. The proportion of time when the high significant wave height appeared was different during different months in different lake zones, and it was small from September to November, which would be beneficial to the emergence of cyanobacteria blooms.

Abstract:Waterside convective controlling aquatic greenhouse gases cycle is a common physical process in lakes. However, the physical process was less studied in shallow lakes. This study investigated the waterside convective strength, which was expressed with a waterside convective velocity scale (w^*), in a large (area 2400 km²) and shallow (mean depth 1.9 m) lake based on in-situ high-frequency monitoring data. Results showed that the w^* with an annual mean value of 2.49 mm/s was relatively uniform in space. However, the w^* had an obvious diurnal variation, the value in nighttime was about four times higher than that in daytime. Meanwhile, the w^* varied seasonally, the peak value generally occurred in summer and lowest in winter. It should be noted that the diurnal variation of w^* was more significant compared to the seasonal variation. Our results also demonstrated that daytime w^* was driven by wind speed, and nighttime w^* was driven by energy budget.

Abstract:The compositions of hydrogen and oxygen stable isotopes (δD and δ¹⁸O) in lake water are important proxies to study regional precipitation and hydrological cycle. At present, the research on hydrogen and oxygen stable isotopes of lake water mainly focused on a single lake. In this study, combined with hydrogen and oxygen stable isotopes in local summer precipitation, the lake salinity, the elevation and latitude of the lakes, 33 lake water samples collected in western China in the summer of 2016 were used to investigate the spatial variations of δD and δ¹⁸O in water of 33 lakes and their controlling factors. The results showed that the compositions of δD and δ¹⁸O in lake water dominated by precipitation. Due to the influence of evaporation on isotopic fractionation, the stable isotope slope and intercept of Lake Water Line in western China are below these of the Global Meteoric Water Line. Spatial distribution of the hydrogen and oxygen isotopes in 33 lake waters varies in different regions, which is mainly controlled by the hydrogen and oxygen isotope components of meteoric waters in different regions rather than lake salinity. The hydrogen and oxygen isotopes of lake waters in the Tibetan Plateau are characterized by “high north and low south”, which is caused by different water vapor sources and evaporation between the north and south of the Tibetan Plateau. In northwestern Xinjiang affected by westerlies, the hydrogen and oxygen stable isotopes are negative, while the lake water isotopes in Inner Mongolia and adjacent areas controlled by East Asia monsoon are positive subjected to evaporation fractionation. The d_excess of lake waters in different regions may reflect diverse water vapor source rather than the evaporation effects of lake water. Influenced by the precipitation, the compositions of hydrogen and oxygen isotopes in the lakes of the Tibetan Plateau are negatively correlated with altitude and positively correlated with latitude.

Abstract:The frequent use of pesticides promotes the agricultural economy, but also brings a lot of environmental problems. When entering the environment from agricultural activities, pesticides can migrate and transform in different ways, finally sank into the lake by runoff, damaging ecological environment and affecting human health. Therefore, it is necessary to study the distribution and fate of pesticides in lake watershed ecosystem. Fugacity-based fate models could provide an effective approach of transportation behavior and fate of pesticides in environmental. The concept of "fugacity" is used to describe the chemical activity of pollutants between different environmental media, so that the simulation results are based on physicochemical properties of chemicals and environmental system. Fugacity models can not only predict residual levels of pesticides in various environmental media, but also reveal spatial distribution features, and will be an important tool for lake watershed ecosystem management. This article reviews its theoretical basis and introduces development status of fugacity models in recent years, and analyses their application in pesticides research and lake watershed ecosystem management, then puts forward the application prospect of the fugacity models in pesticides research. The studies would provide scientific and technical supports in pesticides control and management.