Study on Phytoplankton Community Structure and Environmental Factors in the Qiputang River

Qiputang is a key river of plain river network areas,characterized by water exchange between Yangchenghu Lake and the Yangtze River in Suzhou city,China. To assess its current status,phytoplankton species composition,abundance,community structure and diversity were investigated in September,2011.Furthermore,therelationshipbetweenphytoplanktoncommunityand environmental factors were conducted as well.A total of 113 phytoplankton species were identified,belonging to 57 genera and 6phyla.The percentage of species of Chlorophyta,Bacillariophyta,Euglenophyta and Cyanophyta changed from 51.33%,17.70%,15.04% to 10.62% respectively.The dominant group composed of Cyanophyta,Chlorophyta and Bacillariophyta species varied considerably from Yangchenghu Lake to the Yangtze River in the season,which was detected by dominance analysis.There were significant differences of the phytoplankton abundance among Yangchenghu Lake,Qiputang mainly waterway and estuary ecotone,as determined by one-way analysis of variance(F=3.83,p=0.03).Principal Component Analysis(PCA)and Canonical correspondence analysis(CCA)showed that water temperature,total nitrogen,ammonia nitrogen,total phosphorus and permanganate indexes were the main environmental factors correlated with the phytoplankton community.The CCA ordination plots could well reveal the phytoplankton community structure and its relationships with environmental factors.According to the dominant group of phytoplankton,evaluation results to determine the water quality in Qiputang river quality belong to eutrophic type.