Relationship between Community Structure of Phytoplankon and Water Quality in Yeyahu Lake,Beijing

Studies on community structures of phytoplankon,including species richness,density and biodiversity indices,and correlation analysis between community index of phytoplankton and water quality parameters were carried out from April to November of 2011 in 6 sampling points of 4 sampling areas in Yeyahu Lake,Beijing.Water quality of Yeyahu Lake was also assessed by fixed Carlson index and biodiversity indices.The results showed that 116 species of algae were found from April to November,of which 76.72% were Chlorophyta,Bacillariophyta and Euglenophyta.There was great seasonal variation in phytoplankton assemblage composition,cell density and biodiversity index.In summer and autumn,the water temperature was higher than spring and winter,the phytoplankton species was richer.Chlorophyta and Bacillariophyta were dominant and each composed of 40.73% and 26.96% of the phytoplankton species,followed by Cyanophyta,which composed of 17.56%.In spring and winter,the water temperature was low,only relatively few species of phytoplankton were found.Chlorophyta and Bacillariophyta were also dominant.The sum of Phytoplankton cell density in each sampling plot reached a peak value in June.While the lowest in November.Respectively were 36 119.9×10 4 cells/L and 5 209.75×10 4 cells/L.Phytoplankton density was maximum in summer and fall,so as the seasonal variation of phytoplankton species composition.As the increasing temperature and nutrients,the specie abuandance and density were increasing;Cyanobacteria was dominant in all year,followed by Chlorophyta.The annual mean cell densities of algae fromⅠpart to Ⅳ part were 4 881.36×10 4 cells/L,1 015.22× 10 4 cells/L,4 875.00×10 4 cells/L,2 466.00×10 4 cells/L,respectively,of which 99.83% were Chlorophyta and Cyanophyta,the Oscillatoria tenuis,Spirulina major,Chroococcus minutus and Dactylococcopsis acicularis were dominated in the algae community from April to November.Seasonal variability was the same for the indices of Shannon-Wiener index and Pielou index.And they were higher in May,November,but lower in June,October.Shannon-Wiener indexes of May and November were 2.16 and 2.09 respectively;Shannon-Wiener indexes of June and October,were 1.45 and 1.40 respectively,So the water quality in spring and winter was better;while the water quality was worse in summer and autumn.Shannon-Wiener diversity index and Pielou index were highly significant positive correlation (p0.01).The species diversity indices of Yeyahu Lake,may be more due to community evenness changes rather than species abundance.The algae diversity indexes of species Shannon-Wiener fromⅠpart to Ⅳ part were 1.524,1.956,1.786 and 2.014,respectively.According to values of algae comprehensive index,Yeyahu Lake has suffered serious pollution and can be regarded as eutrophication status.Logarithm density of algae was positively correlated with total nitrogen content (p0.01),and species richness was correlated with water temperature and total nitrogen content (p0.05).Both water temperature and total nitrogen content were the major factors affecting the community structure of phytoplankton of Yeyahu Lake.