Eutrophication and water quality characteristics of Western Chaohu Lake in winter via planktonic alga diversity analysis

Grid sampling method was employed to collect the planktonic alga from western half of Chaohu Lake in winter. The individuals, chlorophyll content and community structure of planktonic alga were determined and identified. The results show that positive correlation is observed between chlorophyll contents and alga density. Both chlorophyll contents and alga density decrease gradually from the estuaries to other parts of the lake, and this tendency is also found in the vicinity of Gushan island, one of the islands in the lake. The predominant phylum is Cyanophyta, and the dominant species include Microcystis， Euglena， Chlorella， Melosira and Anabaena. Moreover, the contamination status and the degree of eutrophication in the lake were evaluated by using various biological assessment methods including chlorophyll content, index of chlorophyll contents, index of special planktonic alga, and diversity indexes (Shannon-weaver, evenness, abundance and dominance). The results indicate that the western half lake is moderately nutritional and lightly contaminated, and that an elevated degree of eutrophication and contamination is observed in the estuaries of the lake and the vicinity of the island.