Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophica-tion process, water quality decreased and lake's ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970's, most of lakes were in the mesotrophic status, mesotrophic water area accounted for 91.8%. With the nine year of 1978-1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hyper trophic status of the 40 surveyed lakes. Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now. Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.     

Agricultural Risk Factors Influence Microbial Ecology in Honghu Lake

Agricultural activities, including stock-farming, planting industry, and fish aquaculture,can affect the physicochemical and biological characters of freshwater lakes. However, the effects of pollution producing by agricultural activities on microbial ecosystem of lakes remain unclear.Hence, in this work, we selected Honghu Lake as a typical lake that is influenced by agriculture activities. We collected water and sediment samples from 18 sites, which span a wide range of areas from impacted and less-impacted areas. We performed a geospatial analysis on the composition of microbial communities associated with physicochemical properties and antibiotic pollution of samples. The co-occurrence networks of water and sediment were also built and analyzed. Our results showed that the microbial communities of impacted and less-impacted samples of water were largely driven by the concentrations of TN, TP, NO_3^--N, and NO_2^--N, while those of sediment were affected by the concentrations of Sed-OM and Sed-TN. Antibiotics have also played important roles in shaping these microbial communities: the concentrations of oxytetracycline and tetracycline clearly reflected the variance in taxonomic diversity and predicted functional diversity between impacted and less-impacted sites in water and sediment samples, respectively. Furthermore, for samples from both water and sediment, large differences of network topology structures between impacted and less-impacted were also observed. Our results provide compelling evidence that the microbial community can be used as a sentinel of eutrophication and antibiotics pollution risk associated with agricultural activity; and that proper monitoring of this environment is vital to maintain a sustainable environment in Honghu Lake.     

A comprehensive census of lake microbial diversity on a global scale

Despite recent interest in microbial diversity and community structure of lakes across various spatial scales, a global biogeographic distribution pattern and its controlling factors have not been fully disclosed. Here, we compiled and analyzed 88,334,735 environmental 16S rRNA sequences from 431 lakes across a wide range of geographical distance and environmental conditions(in particular, salinity, 0–373.3 gL~(–1)). Our results showed that lake sediments inhabit significantly(ANOVA: P0.001) more diverse microbial communities than lake waters. Non-metric dimensional scaling(NMDS) ordinations indicated that microbial community compositions differed distinctly among sample types(freshwater vs. saline, water vs. sediment) and geographic locations. Mantel and partial Mantel tests showed that microbial community composition in lake water was significantly(P=0.001) correlated with geographic distance, salinity, and pH. Statistical analyses based on neutral community and null models indicated that stochastic processes may play predominant roles in shaping the microbial biogeographic distribution patterns in the studied global lake waters. The dispersal-related stochasticity(e.g., homogenizing dispersal) exhibited a stronger influence on the distribution of microbial community in freshwater lakes than in saline lakes. Overall, this work expands our understanding of the impact of geographic distance, environmental conditions, and stochastic processes on microbial distribution in global lakes.     

Fish manipulation as a lake restoration tool in shallow,eutrophic temperate lakes 1: cross-analysis of three Danish case-studies

The use of fish manipulation as a tool for lake restoration in eutrophic lakes has been investigated since 1986 in three shallow, eutrophic Danish lakes. The lakes differ with respect to nutrient loading and nutrient levels (130–1000 μg P l⁻¹, 1–6 mg N l⁻¹). A 50% removal of planktivorous fish in the less eutrophic cyanobacteria-diatom dominated Lake V?ng caused marked changes in lower trophic levels, phosphorus concentration and transparency. Only minor changes occurred after a 78% removal of planktivorous fish in eutrophic cyanobacteria dominated Frederiksborg Castle Lake. In the hypertrophic, green algae dominated Lake S?byg?rd a low recruitment of all fish species and a 16% removal of fish biomass created substantial changes in trophic structure, but no decrease in phosphorus concentration. The different response pattern is interpreted as (1) a difference in density and persistence of bloomforming cyanobacteria caused by between-lake variations in nutrient levels and probably also mixing- and flushing rates, (2) a difference in specific loss rates through sedimentation of the algal community prevaling after the fish manipulation, (3) a decreased impact of planktivorous fish with increasing mean depth and (4) a lake specific difference in ability to create a self-increasing reduction in the phosphorus level in the lake water. This in turn seems related to the phosphorus loading.     

How Microbes Shape Their Communities? A Microbial Community Model Based on Functional Genes

Exploring the mechanisms of maintaining microbial community structure is important to understand biofilm development or microbiota dysbiosis. In this paper, we propose a functional gene-based composition prediction(FCP) model to predict the population structure composition within a microbial community. The model predicts the community composition well in both a low-complexity community as acid mine drainage(AMD) microbiota, and a complex community as human gut microbiota. Furthermore, we define community structure shaping(CSS) genes as functional genes crucial for shaping the microbial community. We have identified CSS genes in AMD and human gut microbiota samples with FCP model and find that CSS genes change with the conditions. Compared to essential genes for microbes, CSS genes are significantly enriched in the genes involved in mobile genetic elements, cell motility, and defense mechanisms, indicating that the functions of CSS genes are focused on communication and strategies in response to the environment factors. We further find that it is the minority, rather than the majority, which contributes to maintaining community structure. Compared to health control samples, we find that some functional genes associated with metabolism of amino acids, nucleotides, and lipopolysaccharide are more likely to be CSS genes in the disease group. CSS genes may help us to understand critical cellular processes and be useful in seeking addable gene circuitries to maintain artificial self-sustainable communities. Our study suggests that functional genes are important to the assembly of microbial communities.     

Stratification of alkaline phosphatase in sediments of two urban lakes and its effect on phosphorus cycle

Phosphorus loadings in sediments play an important role in lake eutrophication and the progress of its recovery. The phosphorus release is controlled by physical, chemical and biological mechanisms. Alkaline phosphatase catalyzes remineralization of organic phosphorus and then it may be an important factor accelerating phosphorus cycling in sediments. In this paper, distributions, properties and function of alkaline phosphatase with depths in sediments of two urban lakes were discussed. Alkaline phosphatase activity (APA) in the sediments of Lake Yuehu decreased with the sediment depth. APA in sediments of Lake Yuehu was, mostly, inhibited by Phe and L-Cys; and inhibiting ability of Phe could be stronger than L-Cys. APA in deeper layer (20–30 cm) of sediments was more sensitive to the inhibitors than other layers, but range of variation in APA was most wide in the subsurface layer (10–20 cm). All the facts implied that alkaline phosphatase occurred in various forms (isoenzymes). APA in the sediments with different depths of Lake Donghu responded Phe differently. Reacted with Phe and incubated for 1 day, the amounts of SRP released by these sediments varied correspondingly. SRP on the overlying water in deeper layers (5–10 cm and 15–20 cm) of Site T1 was higher than that in surface layer (0–5 cm) of the same site, 1 day after incubation. Hence, the SRP release resulted, at least partially, from the hydrolysis of some liable organic phosphorus mediated by APA. Alkaline phosphatase in lake sediments plays an important role in the release of internal phosphorus loadings and eutrophication. A possible explanation for the sensitivity at deeper layers could be another active region of hydrolysis by alkaline phosphatase from organic phosphorus, which added a new dimension in phosphorus cycling mediated by some biochemical mechanisms.     

Latitudinal changes in species diversity of permafrost wetland plant communities in Great Xing’an Mountain valleys of Northeast China

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude (P < 0.01), but decreased significantly in the shrub layer (P < 0.01). Species composition and the orders of dominant species in the plant communities by importance value changed along latitude. Latitudinal changes of α-diversity in permafrost wetland plant communities were different in the herb and shrub layers. With decreasing latitude, species richness and species diversity increased in the herb layer; but decreased in the shrub layer. The opposite patterns were found for species dominance. Species evenness in the shrub layer decreased with decreasing latitude. ?-diversity in the herb and shrub layers decreased first, and then increased, and finally decreased with increasing latitude. Species composition in the herb layer was similar among the plots at higher latitudes.     

Latitudinal changes in species diversity of permafrost wetland plant communities in Great Xing’an Mountain valleys of Northeast China

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude (P < 0.01), but decreased significantly in the shrub layer (P < 0.01). Species composition and the orders of dominant species in the plant communities by importance value changed along latitude. Latitudinal changes of α-diversity in permafrost wetland plant communities were different in the herb and shrub layers. With decreasing latitude, species richness and species diversity increased in the herb layer; but decreased in the shrub layer. The opposite patterns were found for species dominance. Species evenness in the shrub layer decreased with decreasing latitude. ?-diversity in the herb and shrub layers decreased first, and then increased, and finally decreased with increasing latitude. Species composition in the herb layer was similar among the plots at higher latitudes.     

Analysis of forestry impacts and biodiversity in two Pyrenean forests through a comparison of moth communities （Lepidoptera, Heterocera）

We have compared the biodiversity variations in moth communities between unmanaged forests and commercial forests in a mountainous environment （Pyrenees France）. The aim was to evaluate the impact of forestry activities on moth diversity. The data collected from the insects were analysed with a Bayesian specific similarity index （noted SSP index） and by statistical biodiversity indexes comparison. It was seen that diversity and richness were decreased in the plantation compared to the unmanaged forest. Interestingly, the composition of the communities of moths was shown to be not only related to the presence/absence of host plants, but also to be in relation with changes in the differences in forest architecture （i.e. the relative coverage by the different vegetation levels）. However, the moth community in the commercial forest still has a high capacity to converge with the moth community present in more natural forests. We report here a list of 177 species of moths, providing information on the distribution of some uncommon species, poorly studied as yet in the Pyrenees.     

Structure of the Phytoplankton Community and Its Relationship to Water Quality in Donghu Lake, Wuhan, China

The phytoplankton community structure, in terms of species composition, total standing crop,and abundance of the dominant algal species, at four stations in Donghu Lake, Wuhan, China, was investigated monthly from January 1994 to December 1996. A total of 260 taxa was observed, of which Chlorophyta (106 taxa) contributed the highest portion of the total number of taxa, followed by Bacillariophyta (82 taxa)and Cyanophyta (32 taxa). The total standing crop measured by means of chlorophyll a content, cell density,and cell biovolume, as well as the abundance of the dominant species, declined in the order of Station I to Station Ⅳ. Seasonal changes of the standing crop varied greatly among the four stations. Although the cell density at the four stations showed a single peak within a year, the peak density varied from July to November, dependent on the sampling year and the station. For chlorophyll a content and cell biovolume,multiple peaks were observed at Stations Ⅰ and Ⅱ, but a single peak was found at Stations Ⅲ and Ⅳ. The phytoplankton community structure indicated that the trophic status was the highest at Station Ⅰ (most eutrophic), followed by Station Ⅱ; Stations Ⅲ and Ⅳ were the least trophic areas. The long-term changes in phytoplankton community structure further suggested that changes in phytoplankton community structure were correlated with water quality, and eutrophication of Donghu Lake had been aggravated since the 1950s.     

Structure of the Phytoplankton Community and Its Relationship to Water Quality in Donghu Lake, Wuhan, China

The phytoplankton community structure, in terms of species composition, total standing crop,and abundance of the dominant algal species, at four stations in Donghu Lake, Wuhan, China, was investigated monthly from January 1994 to December 1996. A total of 260 taxa was observed, of which Chlorophyta (106 taxa) contributed the highest portion of the total number of taxa, followed by Bacillariophyta (82 taxa) and Cyanophyta (32 taxa). The total standing crop measured by means of chlorophyll a content, cell density,and cell biovolume, as well as the abundance of the dominant species, declined in the order of Station I to Station IV. Seasonal changes of the standing crop varied greatly among the four stations. Although the cell density at the four stations showed a single peak within a year, the peak density varied from July to November, dependent on the sampling year and the station. For chlorophyll a content and cell biovolume,multiple peaks were observed at Stations I and II, but a single peak was found at Stations III and IV. The phytoplankton community structure indicated that the trophic status was the highest at Station I (most eutrophic), followed by Station II; Stations III and IV were the least trophic areas. The long-term changes in phytoplankton community structure further suggested that changes in phytoplankton community structure were correlated with water quality, and eutrophication of Donghu Lake had been aggravated since the 1950s.     

Detrital aggregates in some Iowa lakes and reservoirs

Detrital aggregates in three eutrophic Iowa lakes and four eutrophic Iowa reservoirs were studied with light and scanning electron microscopy to determine if aggregate morphologies and concentrations were similar. Lake and reservoir aggregates were composed of organic and inorganic particles bound together in an organix matrix. Many of the inorganic particles were calcium carbonate. Obvious bacterial and fungal attachment to the aggregates was rare. Aggregate concentrations ranged from 4 to 274 million aggregates per liter. Aggregates smaller than 18 μm diameter dominated the hyperbolic size-frequency distribution of aggregates in all lakes. Reservoir and lake aggregate concentrations did not differ significantly, but mean aggregate concentrations were directly correlated to the mean chlorophyll a concentration of the lakes. These data strongly suggest that detrital aggregate concentrations are influenced by the trophic status of a lake. Journal Paper No. J-8705 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 2051. Journal Paper No. J-8705 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 2051.     

Investigation of bacterial community diversity in water of Zoige Alpine Wetland

Spatial isolation is currently thought to represent one of the major factors resulting in bacteria genetic variation and population abundance. The bacterial diversity in a distinct environment Zoige Alpine Wetland located in the northeast of the Qinghai-Tibetan Plateau with the altitude 3400 m on average aroused our great attention. This area belongs to Qinghai-Tibetan cold climate zone with the mean annual temperature about 1 °C. Although several studies on bacterial diversity in Qinghai-Tibetan Plateau had been reported, there is no report on wetland water in this area. In this work, six water samples were collected and the water qualities including COD_Cr, NH₄⁺-N, NO₃^--N, NO₂^--N, TN, TP, TOC were investigated, of which results indicated that more than 80% samples sorted as II–V class of surface water sources according to the National Water Quality Standard of China (GB3838-2002). Comparison of bacterial communities among the six samples was analyzed by DGGE of PCR-amplified 16S rDNA with universal bacterial primer sets. The profiles demonstrated that samples from the Flower Lake had more DNA bands than the Conservatory Station inferring higher diversity. In addition, the samples from the same environment shared similar compositions of bacterial communities. Bacterial community composition and predominant bacteria were analyzed by 16S rDNA clone library. The dominant group was Proteobacteria (51.6% of the total clones, which contained 24.2% alpha proteobacteria, 14.5% beta proteobacteria and 12.9% gamma proteobacteria). And the Bacteroidetes added to 17.7%, Verrucomicrobia to 4.8%. More than 24.2% of the total clones showed high similarity to uncultured bacteria. The above work provides some information on bacterial diversity for special site of spatial isolation.     

Investigation of bacterial community diversity in water of Zoige Alpine Wetland

Spatial isolation is currently thought to represent one of the major factors resulting in bacteria genetic variation and population abundance. The bacterial diversity in a distinct environment Zoige Alpine Wetland located in the northeast of the Qinghai-Tibetan Plateau with the altitude 3400 m on average aroused our great attention. This area belongs to Qinghai-Tibetan cold climate zone with the mean annual temperature about 1 °C. Although several studies on bacterial diversity in Qinghai-Tibetan Plateau had been reported, there is no report on wetland water in this area. In this work, six water samples were collected and the water qualities including COD_Cr, NH₄⁺-N, NO₃^--N, NO₂^--N, TN, TP, TOC were investigated, of which results indicated that more than 80% samples sorted as II–V class of surface water sources according to the National Water Quality Standard of China (GB3838-2002). Comparison of bacterial communities among the six samples was analyzed by DGGE of PCR-amplified 16S rDNA with universal bacterial primer sets. The profiles demonstrated that samples from the Flower Lake had more DNA bands than the Conservatory Station inferring higher diversity. In addition, the samples from the same environment shared similar compositions of bacterial communities. Bacterial community composition and predominant bacteria were analyzed by 16S rDNA clone library. The dominant group was Proteobacteria (51.6% of the total clones, which contained 24.2% alpha proteobacteria, 14.5% beta proteobacteria and 12.9% gamma proteobacteria). And the Bacteroidetes added to 17.7%, Verrucomicrobia to 4.8%. More than 24.2% of the total clones showed high similarity to uncultured bacteria. The above work provides some information on bacterial diversity for special site of spatial isolation.     

Community characteristics and population structure of Ferrocalamus strictus,a rare species in Mojiang,Yunnan, China北大核心CSCD

Aims As an endangered wild species with extremely small populations, Ferrocalamus strictus is narrowly distributed in South Yunnan with a small number of individuals. The survey of population structure and community characteristics of the wild population of F. strictus can facilitate understanding its endangered system and mechanisms and provide preliminary research basis for its protection. Methods We investigated the community and population structure of F. strictus, including species composition, population density, population survivorship curve and death factors by plot surveying and sampling. Important findings The community in which population of F. strictus is located in Mojiang has some characteristics of mountain rainforests in terms of appearance and species composition. The population density of F. strictus was 2.04 ind.·m–2. The survivorship curve of F. strictus was between Deevey-I and Deevey-II. The net proliferation rate (R0) of F. strictus population was 1.10, which indicates an expanding population of F. strictus. The death of F. strictus is caused by human logging, natural death, shoot degradation and insects feeding. Among them, artificial cutting accounts for the largest proportion. Ferrocalamus strictus is a species of forest bamboos distributed in the South Asian subtropics, which is a medium-sized bamboo species. Its internode length change suddenly from the base 3–4 nodes. The longest ones exceed 1 m, which ranks at the top of all bamboo species and is closely related to its adaptation to the tropical mountain rainforest environment. © Chinese Journal of Plant Ecology.     

Temporal and spatial distribution of biogenic silica and its significance in the Wuliangsuhai Lake and Daihai Lake

In this work, the concentrations, temporal and spatial distributions and the relationship between biogenic silica (BSi) and primary productivity are discussed on the basis of the geochemistry character of BSi in the water–sediment system of the Wuliangsuhai Lake and Daihai Lake. The results show that the average concentrations of SiO₃^2- and BSi are 3.0 mg/L and 3.5 mg/g in the overlying water and sediments from the Wuliangsuhai Lake, respectively, while they are 1.0 mg/L and 7.5 mg/g, respectively, in the Daihai Lake. It is the uptake and assimilation of diatom phytoplankton which results in the significant difference of the SiO₃^2- concentrations between the two lakes, and the inputs of surface runoff is one of the important factors in impacting the spatial distributions of SiO₃^2- in the overlying water. The spatial distributions of BSi suggest the Si source of the two lakes and indicate the differences of eutrophication types and ancient primary producer between the two lakes. The eutrophication precesses and ancient primary productivity of diatom phytoplankton are reconstructed by applying the geochemistry information of BSi archived in the vertical concentration profiles in the two lake sediments. The geochemistry information of BSi well responds to the paleoenvironment and paleoclimate of the Daihai drainage basin indicating silicate limitation of primary productivity by diatoms phytoplankton in the Daihai Lake.     

Temporal and spatial distribution of biogenic silica and its significance in the Wuliangsuhai Lake and Daihai Lake

In this work, the concentrations, temporal and spatial distributions and the relationship between biogenic silica (BSi) and primary productivity are discussed on the basis of the geochemistry character of BSi in the water–sediment system of the Wuliangsuhai Lake and Daihai Lake. The results show that the average concentrations of SiO₃^2- and BSi are 3.0 mg/L and 3.5 mg/g in the overlying water and sediments from the Wuliangsuhai Lake, respectively, while they are 1.0 mg/L and 7.5 mg/g, respectively, in the Daihai Lake. It is the uptake and assimilation of diatom phytoplankton which results in the significant difference of the SiO₃^2- concentrations between the two lakes, and the inputs of surface runoff is one of the important factors in impacting the spatial distributions of SiO₃^2- in the overlying water. The spatial distributions of BSi suggest the Si source of the two lakes and indicate the differences of eutrophication types and ancient primary producer between the two lakes. The eutrophication precesses and ancient primary productivity of diatom phytoplankton are reconstructed by applying the geochemistry information of BSi archived in the vertical concentration profiles in the two lake sediments. The geochemistry information of BSi well responds to the paleoenvironment and paleoclimate of the Daihai drainage basin indicating silicate limitation of primary productivity by diatoms phytoplankton in the Daihai Lake.     

Nitrogen transformations in stratified aquatic microbial ecosystems

New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a μm–mm scale. A large and ever-expanding knowledge base about nitrogen fixation, nitrification, denitrification, and dissimilatory reduction of nitrate to ammonium, and about the microorganisms performing the processes, has been produced by use of these techniques. During the last decade the discovery of anammmox bacteria and migrating, nitrate accumulating bacteria performing dissimilatory reduction of nitrate to ammonium have given new dimensions to the understanding of nitrogen cycling in nature, and the occurrence of these organisms and processes in stratified microbial communities will be described in detail.     

Phyllosphere eukaryotic microalgal communities in rainforests:Drivers and diversityOA

Phyllosphere algae are common in tropical rainforests,forming visible biofilms or spots on plant leaf surfaces.However,knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity is limited.The aim of this study is to identify the environmental factors that drive phyllosphere algal community composition and diversity in rainforests.For this purpose,we used single molecule real-time sequencing of full-length 18S rDNA to characterize the composition of phyllos...     

Studies on Temporal and Spatial Variations of Phytoplankton in Lake Chaohu

Temporal and spatial variations of the phytoplankton assemblage in Lake Chaohu, a large shallow eutrophic lake in China, were studied from September 2002 to August 2003. A total of 191 phytoplankton species was identified, among which Chlorophytes （101） ranked the first, followed by Cyanophytes （46） and Bacillariophytes （28）. On aver- age over the entire lake, the maximum total algal biomass appeared in June （19.70 mg/L） with a minimum （5.05 mg/ L） in November. In terms of annual mean biomass, cyanobacteria contributed 45.43% to total algal biomass, followed by Chlorophytes （27.14%）, and Bacillariophytes （20.6%）. When nitrate （NOs-N） and ammonium （NH4-N） concentrations dropped in spring, fixing-nitrogen cyanobacterium （Anabaena） developed quickly and ranked the first in terms of biomass in summer. It is likely that dominance of zooplanktivorous fish and small crustacean zooplankton favored the development of the inedible filamentous or colony forming cyanobacteria. The persistent dominance of cyanobacteria throughout all seasons may indicate a new tendency of the response of phytoplankton to eutrophication in Lake Chaohu.