Abstract:The complicated changing water-sediment exchange relationship between the Yangtze River and its naturally connected lakes, Lake Dongting and Lake Poyang, have affected regional flood disaster control, water resources and water environmental protection and maintenance of water ecological security, which has become the core of water problems in the middle reaches of the Yangtze River. The progress of research on river-lake relationship between the Yangtze River and its connected large lakes was systematically reviewed from the point of view of the concept and connotation of river-lake interaction, the evolution process, the influencing factors and effects of changing river-lake relationship. Based on the problems in current research, the following research issues were proposed:how to define a comprehensive index for the river-lake relationship is the premise to correctly understand the relationship between rivers and lakes; how to quantify the effects of human activities and climate change contributions is the emphasis and difficulty of research on the river-lake relationship; it is a long-term task to track the impact of the Three Gorges Project on the river-lake relationship; and it is the ultimate goal to maintain healthy river-lake system pattern in the middle reaches of the Yangtze River which benefits both the Yangtze River and its connected lakes based on the optimization and controlling principles on joint operation of hydraulic engineering group for large river-lake water systems.

Abstract:The predominance of nitrogen fixing cyanobacteria in the eutrophic aquatic systems is related to many environmental factors, such as nutrient forms and concentrations, nitrogen to phosphorus ratio, water temperature and trace metal. The nitrogen fixing cyanobacteria dominated in lakes with the concentration of orthophosphate above 0.01mg/L, the concentration of dissolved inorganic nitrogen under 0.1 mg/L, furthermore, the lower ratio of nitrogen to phosphorus was suggested to indicate the occurrence of the nitrogen fixing cyanobacteria, but the differentiation mechanism of nitrogen fixing and non-nitrogen fixing cyanobacteria need a deep research. Moreover, cyanobacteria nitrogen fixing rates can be influenced by the light availability, inorganic nitrogen concentrations, heterocyst abundance and the fixed nitrogen determines the contribution to the pools of nitrogen. The nitrogen fixing cyanobacteria is the important contributor to the pools of nitrogen in the ocean systems, but in the eutrophic lakes, its contribution is still in dispute. Thus, this paper reviewed the researches on nitrogen fixing cyanobacteria to attract attention of scientist on its important contribution to the pool of nitrogen in aquatic systems.

Abstract:Excessive nitrogen loading has been regarded as one of the most important factors causing eutrophication of lakes. The traditional views show that when nitrogen deficiency occurs, lake ecosystems can obtain nitrogen from the atmosphere through biological nitrogen fixation to meet their nitrogen needs, so according to this assumption, the main limiting factor of the primary productivity of water bodies is phosphorus availability. However, recent research has shown that nitrogen fixation does not meet ecosystem demands, and nitrogen or nitrogen and phosphorus limitation are generally accepted. Furthermore, eutrophic lakes often exhibit nitrogen limitation, meaning that they are sensitive to additional nitrogen inputs. In this paper, research on the polluting effects of nitrogen in Lake Taihu was reviewed. Both the internal and external loadings of nitrogen to the lake were considered. The nitrogen inputs from the three main sources, i. e. input from rivers, precipitation from atmosphere and release from sediments, were analyzed. The results show that there is obvious spatial heterogeneity in nitrogen pollution of Lake Taihu. The pollution is relatively heavy in the western and northern parts of the lake and relatively light in the southeastern part. River input is a major source of nitrogen loading to the lake. Internal loading is also an important source of nitrogen pollution. However, to release a quantity estimate is mainly based on the amount of sediment resuspension, and about the release quality, how many percentage can be used by phytoplankton is still not clear, especially the particulates mineralization rates. The cycling nitrogen in lakes mostly mediate by nitrification, denitrification, nitrogen fixation and anammox. In Lake Taihu, the process of biological nitrogen fixation has been found to contribute little to the total annual input of nitrogen and denitrification is the main process through which nitrogen is removed from the lake.

Abstract:Dynamic of water level is the key factor to affect the hydrological processes and ecological environment in lakes. Based on the EFDC model, a two-dimensional model comprising the Lake Poyang Project and the main lake is constructed to simulate the impact of Lake Poyang Project on dynamics of water level in the main stem and the wetland nature reserve. Simulation results show that:the impact of Lake Poyang Project on water level is gradually reduced from north to south, and water level in the northern part of the lake is raised due to the project, which decreases the north-south water level difference and affects the flow rate and the water purification capacity. The impact of Lake Poyang Project on the core area of Wucheng and Nanji Nature Reserve is little:the core area of Wucheng Nature Reserve is separated from the main lake and not affected by the project when the water level is lower than 13.8 m, but the time of separation will be affected by the project; while the core area of Nanji Nature Reserve is located in the southern part of the lake, and the impact of the project is little. In the dry year, the dynamic of water level is the same as that in the normal year due to the regulation of the project. The impact of Lake Poyang Project on dynamic of water level is larger in the dry year than that in the normal year, but the impact on the southern part is still little in dry year. The simulation result can reveal the law of the impact of Lake Poyang Project on dynamic of water level with the existing regulation scheme, and provide some reference for the construction of the project.

Abstract:Taking MOD13Q1(vegetation indices 16-day L3 globe 250 m) dataset, which is a data production composited by Terra/MODIS of 11 years as a main data source of Lake Dongting, the water surface area of Lake Dongting were extracted by setting threshold values on NDVI(Normalized Difference Vegetation Index) and NIR(Near InfraRed). Under the background of the Three Gorges Project, combined with the data of water area and water level, the paper analyzed the interannual variation features and the variation rule within a year of water area in Lake Dongting, and deeply explored the quantitative relationship between water level and water surface area by integrating with water level data of Chenglingji hydrological station. The result indicated that the Three Gorges Project largely controls the water yield from the Yangtze River into Lake Dongting; Under the effects of climate change and the operation of Three Gorges Project, Lake Dongting area has a decreasing trend on the whole; The fitting result indicates that water surface area has good correlation with water level and the deterministic coefficient of the fitting curves was 0.975 from 2000 to 2003.

Abstract:From starting of diversions of lower reaches of Qarqan River, in 1989, there has been a lot of small lakes in the north side of the new riverbed, drives fluctuated changes of water area patterns in Tetima-Kanglayka lakes region. Since Emergency Ecological Water Transfusion(EEWT) project in lower reaches of Tarim River started in 2000, there are large water area began to reappear and expand in old Tetima lake bed, where there was dried up over than 30 years since a water caused by construction of Dashkol Reservoir. The lakes are already in stable position in Kanglayka region, but there are still big changes of water area in Tetima lake region, when the river diversions are finished in autumn 2002. In this paper, the water area change process and its change trend in Tetima-Kanglayka lakes region was analyzed in high temporal resolution based on a serial, 102 times, remotely sensed imageries which acquired from 1972 to 2012. A further study carried on integrated the result with runoff and transformed water amount data to find out dominant drivers of the changes. We concluded that water area landscape pattern changes was caused by interannual changes of Qarqan River run-off during 1970s till 2000, and has been controlled by the EEWT project in the lower reaches of the Tarim River till the end of research period.

Abstract:Lake Bosten is the largest inland freshwater lake of China and plays a key role in the local arid-area ecosystem. The amount and quality of the water Lake Bosten are vital to the people in the oasis based socio-economic system the lake supportted. However, the environmental problems of Lake Bosten emerged are getting worse day by day resulted from the large variation of water level and worse and worse water quality, which were focused by the government and scholars. This study focuses on the dynamics of water-salinity of Lake Bosten in the past 60 years(1951-2011) and their response to climate change, attempted to predict water level and water quality change trend. The results showed that water level of Lake Bosten in 1951-2011 had a significant increasing trend. Step change points in water level were identified in Lake Bosten, which occurred in the years around 1974 and 1994 dividing the long-term water level series into a stable period(1951-1974), a decreasing period(1975-1994) and an increasing period (1995-2011). Water salinity of Lake Bosten also presented three change stages. And the water level and water salinity showed a significant negative correlation, but the water quality change lagged one year compared with the water level. The temperature in Lake Bosten basin had a significant increasing trend, and its step change point occurred in the year around 1993, which was consistent with the run-off in Kaidu River. The correlation between the temperature and water level, water quality in the Lake Bosten is extremely significant. The temperature regulated the water quality and water level of Lake Bosten through changing the lake inflow and evaporation. The water level will have a decreasing trend and water quality will be worse and worse if the temperature maintain continued rising in the future. Therefore, in order to ensure the sustainable development and utilization of the water resources of Lake Bosten, and inhibit the deterioration of water quality, it should be concentrated the diversion time of Lake Bosten from May to September, and strictly controlled the industrial and agricultural water consumption, reduced the emissions of industrial, agricultural and domestic pollution, decreased the amount of surrounding groundwater development.

Abstract:In order to increase food supply and suppress the ecological degradation, the saline-alkaline land surrounded the Lake Chagan will be developed into the largest irrigated area-Songyuan Irrigation area, in the Songhuajiang-Nenjiang(Songnen) Plain. The area will be 2.84×10⁷ km². The proposed irrigated area is located in the center of saline-alkaline region of the plain. The important objectives include new rice fields, improving the existing dry land of low yields, and recovering grassland and wetland. The drained water from the irrigation area is saline-alkaline water, while the Lake Chagan is a light alkaline lake, the largest lake in the Songnen Plain, and a national natural protection zone. The plants under protection include Phragmites and Suaeda glauca (Bunge), and the animals under protection include Ciconia, Grus leucogeranus, Gruiformes, Aquila chrysaetos, etc. Most birds in the region belong to the first class national protected animals or endangered species. Therefore, the lake is an important base for the biological species and plays an important environmental function in accommodating local climate. In this area, the ecological systems have been seriously degraded, so that some of the land has become the alkaline deserts. Since the Lake Chagan is a conflux center for the ground and surface water, if the tailing water of the irrigation engineering is pumped into the lake directly, the lake biological system would be in serious aftermath. Thus the key issue is how to avoid the ecological risk that the development the irrigation area might bring to the Lake Chagan. For getting both the benefits of protecting the lake biological system and developing the saline-alkaline land, this paper, based on analyses of the risks, has designed five wetland disposal systems as the transition area to deal with the alkaline tailing water. First of all, through degrading and precipitating of the pollutants, the pH of the tailing water was decreased when it enters into the modeling water processing systems. If the salt contents need to be decreased, the tailing water should be mixed with the water deriving from the Songhua River. Only when the tailing water quality meets the standard, the water will be allowed to discharge into the lake. The hazard evaluation indicates that this utilization model would not only not damage the lake ecosystem, but also be conducive to the stabilization of the lake ecosystem. Furthermore, the utilization model could develop saline-alkaline region and promote social economic development in the area.

Abstract:In order to develop a benthic index of biotic integrity for Lake Taihu (LTB-IBI), we seasonally carried out investigation on macroinvertebrate assemblages and their environments at 32 sites in Lake Taihu from spring, 2010 to autumn, 2012. Based on the investigation, we used the method of least disturbed condition and four criteria to define reference sites. LTB-IBI was developed separately for non-central region and central region of Lake Taihu. Metrics were stepwise examined for distribution analysis, discriminating power analysis, relationship with environmental variables and redundancy analysis. The core metrics of LTB-IBI for non-central region were total taxa richness, Simpson diversity index, 3 dominant taxon% and BMWP score. One more metric, i. e. (Crustacea + Mollusca) taxa for central region. LTB-IBI value for non-central region and central region were respectively obtained by summing up core metrics, which were transformed into a uniform score by ratio score method. Health condition of Lake Taihu was found to improve gradually from 2010 to 2012. Total nitrogen was suggested as the major factor affected LTB-IBI. Our results suggest that long-term data would benefit the development of a robust LTB-IBI and its use in practice of Lake Taihu health assessment.

Abstract:The vertical variations of microbial biomass, alkaline phosphatase activity (APA) and phosphate-solubilizing ability of microbes were studied in the sediments from different pollution sources in Lake Fuxian, Yunnan Province. The results showed that the microbial biomass and the APA in the sediment cores generally decreased with the depth and the strongest microbial activity was shown in the surface sediment. The microbial biomass and the APA in the sediments of the mouth of Gehe River in the south shore were the highest among the research sites, which was heavily polluted by the discharge from eutrophic Lake Xingyun. The second highest amounts of the microbial biomass and the APA were found in the sediments of the mouth of Liangwan River with agriculture pollution source and the sediments in the mouth of Dongda River with phosphate mining pollution source. However, the lowest amounts of the microbial biomass and the APA were shown in the sediments of the mouth of Jianshan River with the pollution source of soil erosion. The result of incubation experiment showed that the microbes in the sediments had stronger phosphate-solubilizing ability to dissolve inorganic phosphate than to dissolve organic phosphate. The combination of the amount of inorganic phosphate solubilizing bacteria and the APA determined the potential of phosphorus releasing from sediment, which resulted in high interior phosphorus loading in Lake Fuxian.

Abstract:To understand the distribution characteristic and bioaccumulation factors(BAF) of total mercury(THg) and methylmercury(MeHg) in phytoplankton at Guizhou Plateau reservoirs, southwest of China. The phytoplankton and water samples were investigated at five reservoirs in the winter of 2012. The results showed that diatom was the dominant algae at Guizhou Plateau reservoirs in winter and phytoplankton abundance had obvious difference at the five reservoirs. The maximum phytoplankton abundance was about 29.05×10⁴ cells/L at Lake Baihua dam, and the minimum only 0.49×10⁴ cells/L at Sanbanxi Reservoir. The concentrations of THg and MeHg in phytoplankton were 29.29-277.07 ng/g(dry) and 1.12-10.93 ng/g(dry), respectively. The maximum concentrations of THg and MeHg in phytoplankton was at Lake Baihua. The BAF of THg and MeHg in phytoplankton were 1.42×10⁴-9.78×10⁴ and 3.10×10⁴-4.43×10⁵, respectively. The maximum BAF in phytoplankton of THg was at Lake Baihua. The maximum BAF of MeHg in phytoplankton was at Lake Hongfeng. There was different effect on biological enrichment of mercury and methylmercury for different phytoplankton species composition. There were significant positive correlations between MeHg in phytoplankton and THg, MeHg, dissolved MeHg (DMeHg) in water. No significant correlation was found between MeHg in phytoplankton and the THg, DMeHg in water. MeHg was not only absorbed by phytoplankton. There were other factors influencing Me-Hg concentration in phytoplankton inevitably. There were significant negative correlations between MeHg in phytoplankton and environmental factors (SD, TN, NO₃^--N). The degree of eutrophication had effects on MeHg concentration in phytoplankton.

Abstract:In the present study, we investigated spatial and temporal distributions of sulfate reducing bacteria (SRB) and controlling factors in sediment of Aha Reservoir, Lake Hongfeng and Lake Baihua, Guiyang City based on the most probable number (MPN) method. The results indicate that there were discernible seasonal variations in the SRB content distribution. SRB contents of sediments in winter were much less than those in summer and fall. The peaks of SRB contents occurred in the middle of sediment cores in winter, while SRB generally increased towards the sediment-water interface in June and September. The contents of sulfate in the sediments in Aha Reservoir which has been polluted by acid mine drainage were much higher than those in the other two reservoirs:Lake Hongfeng and Lake Baihua. SRB contents, however, have no discernible spatial variations in the three lakes(reservoirs), except for elevated values only in the surface of sediment in Lake Aha in summer and autumn. This indicates that higher organic matter contents and optimum pH in these reservoirs favor the growth of SRB, and sulfate content was not the main significant factor of SRB growth.

Abstract:The effects of light intensity on seeds germination, seedlings growth and physiology of Ottelia acuminata were studied through simulated experiments in order to explore the reasons for the disappearance of the plant in Lake Dianchi in China and the possibilities of its restoration. The results showed that light intensity had no significant effect on the seeds germination, while the influences of different light intensities on the seedlings growth of O. acuminata were significant. The blades length, blades width and plants height under shading rates of 71.8% and 91.5% were all significantly higher than those under 0% and 97.6% shading rates, and the biomass under that two shading rates were also obviously higher than those under 97.6% shading rate. Our results also showed that light intensity had prominent influence on chlorophyll-a content in the middle period of this research, but no remarkable effects were found in the effect of light intensity on peroxidase activities in the leaves. Chlorophyll-a contents in the leaves under shading rate of 71.8% were significantly higher than those under 0% and 97.6% shading rates. Although low water transparency and weak light intensity caused by eutrophication did not influence the seeds germination of O. acuminata, they affected the seedlings growth and physiological characteristics, which may impact the reproduction of the plant eventually. Therefore, it is necessary to increase the water transparency and improve the light condition in order to restore O. acuminata in Lake Dianchi.

Abstract:Aerobic anoxygenic phototrophic bacteria (AAPB) are photoheterotrophic microbes and play a significant role in carbon cycle in aquatic ecosystems. However, the effect of carbon source on the community structure of AAPB remains unknown presently. This study determined the influence of three carbon sources, glucose, sodium pyruvate and yeast extract common used in microbe isolation and culture on total bacteria and AAPB community structures of Lake Ulansuhai, using denaturing gradient gel electrophoresis based on the genes of 16S rDNA and pufM of photosynthetic reaction center respectively. The results showed that diversity and richness of total bacteria community had been enhanced while those of AAPB community been improved previous to 14 days then decreased, after inducing by different carbon sources for 7-21days. Among the three carbon sources, sodium pyruvate best increased the richness and diversity of both total bacteria and AAPB. Sequencing and phylogenetic analysis revealed that some taxonomic strains were discovered which failed to be determined before induction by carbon source and moreover the abundance of some strains harboring specific carbon metabolism were greatly elevated. These results may promote the appreciation for the function and significance of AAPB and provide the basis for their enrichment, isolation and culture.

Abstract:Water samplings were collected at 76 sites across Heihe River basin during the comprehensive investigation in the summer of 2009 and summer and fall of 2010.242 species, which belong to 8 divisions, 11 classes, 25 orders, 45 families and 94 genera, were identified from these water samplings. Bacillariophyta which makes up of 38.43% of the total number of the species is the dominant group, followed by Chlorophyta and Cyanophyta. Synedra ulna, Dactylococcopsis irregularis and S. acus are dominant species, whose ecological dominances are 0.060, 0.031 and 0.021. And frequencies of their occurrence are 43.42%, 43.42% and 46.05%, respectively. The analysis of biodiversity indicates that the complex and stability of phytoplankton community in middle and downstreams are both higher than those of upstream. The water quality of upstream is of no-pollution or slightly polluted, but slightly or moderately polluted in the middle and downstream. The correlation analysis between basin-wide total phytoplankton abundance and environment factors of water shows that the phytoplankton abundance is positively correlated with water hardness in the upstream while the midstream phytoplankton abundance is not significantly related with any factors. In the downstream, the phytoplankton abundance is negatively correlated with water hardness but positively correlated with nutrient index of the total nitrogen multiply by the total phosphorus (TN×TP). In the whole basin, phytoplankton abundance is positively correlated with total dissolved solids, pH and water hardness. The spatial distribution of phytoplankton in Heihe River basin shows obvious vertical zonality and horizontal zonality corresponding to differentiation characteristics of river hydrological zonation. These results showed the spatial correlationship between phytoplankton communities and their natural environment backgrounds. We hope this research could be favor to make policies to improve the management and sustainable utilization of the aquatic biological resources, to protect the water ecological environment in Heihe River basin and even other continental river basins.

Abstract:Two strains of Aphanizomenon flos-aquae were isolated from spring cyanobacterial blooms in Haigeng Bay which located in the northern part of Lake Dianchi. Both the growth characteristics and heterocyst formation as well as nitrogen fixation ability of A. flos-aquae were investigated under different low concentrations of sodium nitrate, and in nitrogen-free culture medium, respectively. The results showed that A. flos-aquae strains were able to grow in the BG-11 medium with various low concentrations of nitrate, and the biomass reached a very high level. The biomass increased with the nitrate-nitrogen concentration increasing, but there was no significant difference when nitrate-nitrogen concentration was above 0.5 mg/L. Induction of heterocyst differentiation was rapid when A. flos-aquae was cultured in N-deficient BG-11 medium, and after reaching a maximum of 72% approximately, the filament with heterocyst began to swing lower. The total nitrogen in nitrogen-free medium increased gradually as nitrogen fixation proceed, and nitrogen concentration was close to 30 mg/L at day 43.

Abstract:To identify the impact of a great flood event on phytoplankton assemblages and their succession in Gaozhou Reservoir, limnological variables and phytoplankton were investigated from January, 2010 to December, 2011. During flood, a mass of particles were flushed into the reservoir and overlaid the original surface sediment, which suppressed nutrients releasing from sediment. Nutrients concentration, especially phosphorus sharply decreased, and total phosphorus concentration was below 0.01 mg/L. After the flood event, the composition of suspended particles were changed, and water transparency decreased during the next mixing period because of the decreased resuspension of inorganic particles and phytoplankton biomass. The phytoplankton community structure rapidly responded to the significant change in the physical environmental variable. Dominant phytoplankton groups changed from colonial blue-green and large unicell Chlorophyta (Coda H₁ and N_A) to planktonic centric diatoms and dinoflagellates (Coda A, B and L_O). Anabaena mucosa which caused blooms yearly in every spring dry season could not be detected after the flood event.

Abstract:Ecological investigations on the community structure of phytoplankton in 10 large reservoirs of Guangdong Province, which played a great role in water supply, were conducted in January and July, 2012. A total of 207 species of phytoplankton were identified, belonging to 104 genera of 8 phyla, which were classified into 30 phytoplankton functional groups. According to the cluster analysis, the ten reservoirs were separated into four ecological regions. Ecological Region One included Nanshui and Xinfengjiang reservoirs, where dominant groups were Oligotropher-adaptive groups. Ecological Region Two included Feilaixia, Baipenzhu and Fengshuba reservoirs, where dominant groups were Mesotropher-adaptive groups and broad-spectrum groups. Additionally, Ecological Region Three and Four contained Gaozhou, Gongping, Dashuiqiao, Hedi and Tangxi reservoirs, where Gaozhou and Gongping reservoirs were characterized by Eutropher-adaptive groups and broad-spectrum groups, while other reservoirs were dominated by Eutropher-adaptive groups. The representative phytoplankton functional groups were significantly different among four regions, and corresponded well with water nutrient conditions.

Abstract:We have investigated the constitution and abundance of macrozoobenthos in Niyang River, the branch of the Yarlung Zangbo River, Tibet, based on season from 2008 to 2009, and taken quantitative analysis to study spatio-temporal characteristics of phytoplankton and their corresponding to environment using multivariate statistics method. The results are as follows:Firstly, the main macrozoobenthos in Niyang River are phryganea larvae, Radix sp., chironomidae larvae. Secondly, based on the method of Duncan test method, there is no significant difference among four sampling sites and seasons as for total abundance, in addition, total abundance of the macrozoobenthos in Niyang River is descending with the elevation ascending. Thirdly, based on the PCA method, as for the sampling sites, the maximum and the minimum total abudance for the macrozoobenthos appear in sampling site Ⅳ and sampling site Ⅱ respectively, as for the seasons, the maximum and the minimum total abudance for the macrozoobenthos appear in the autumn and the winter respectively. Fourthly, based on the CCA method, the relationship between the environmental factors and the macrozoobenthos could be described as two reaches separately, which are the middle-upper reaches and the middlelower reaches. Last but not least, the paper chooses four factors among eleven environmental factors to explain their relationship with total abundance of macrozoobenthos, the four factors are total dissolved solids, total phosphorus, elevation, and season. The paper also suggests paying close attention to macrozoobenthos and the environment factors mentioned above owing to their important indication function, in order to warrantee the sustainable development of Niyang River aquatorium ecology.

Abstract:It is quite important for lake protection and treatment to find out if thermal stratification in summer has effect on the physical and chemical index of the water body. As for deep plateau lakes, water temperature differs greatly at different times during the day. To understand thermal stratification law and to know if the physical and chemical index such as total phosphorus (TP) and dissolved oxygen (DO) concentration, pH, etc. would vary with thermal stratification, we chose 6 sites of Lake Yangzonghai, a typical deep lake in Yunnan-Guizhou Plateau in summer, then measured water temperature, phycocyanin, DO, pH and chlorophyll-a every meter. At the same time, the layering water samples were also analyzed in the lab, and the concentration of TP was got. The result shows that (1) In the forenoon of summer clear days, the water body had no clear thermal stratification; When it was in the noon, the thermal stratification turned into 4 layers, and then 3 layers; At 14:00, the water body was stably stratified; When the thermal stratification is stable, the thermocline is between 9-13 m; the max temperature difference between epilimnion and hypolimnion is 7.8℃; (2) DO and pH has almost the same vertical stratification trend as the water temperature, and the stratification of DO and pH is synchronize with the water thermal stratification; (3) The algae and phytoplankton stratified with water thermal stratification, but it shows a time lag, the time lag is about 2 hours; (4) The TP is not sensitive to thermal stratification, the concentration of TP only sharply increase when it was very close to the bottom of lake. The concentration of TP is even above 9 m. And the disappearance of thermal stratification does not affect the concentration of TP. The average TP concentration of the whole lake is 0.033 ±0.03 mg/L.