The Diatom Community Distribution And Diatom Index Applicability In Nansi Lake And Dongping Lake

South-to-North Water Diversion Project, which is a significant strategic project to alleviate water shortages in northern China and realize rational allocation of water resources, included the east, middle and west route. The east route mainly provide water supply for the eastern part of the North China Plain and the Shandong Peninsula. Hongze Lake, Luoma Lake, Nansi Lake and Dongping Lake are important water storage lakes and water channels,their water quality and eutrophication status have been key issues related to environmental protection and water conservancy departments.Nansi Lake and Dongping Lakehavebeenemployed in the east route of the South-to-North Water Diversion Project as significant storing lakes and water channels. At present, studies onplanktonic diatom have been well reported, but the report about diatom and itsrelationship with environmental factors in Nansi Lake and Dongping Lake still has been regarded as a negligible plate. Thus, investigationsofdiatom community, distribution characteristics, environmental impact factors and indicating potential in Nansi Lake and Dongping Lake not only provide technical guidance for the east route of the South-to-North Water Diversion Project and pollution control in Nansi Lake and Dongping Lake, but also afford detailed information for researching the impact of the South-to-North Water Diversion Project on diatom in the future.From May 2010 to April 2013, this studyanalyzed the diatom community, distribution characteristics, environmental impact factors and indicating potential in Nansi Lake and Dongping Lake,Results are listed as follows:(1) A total number of 69 diatom species belonging to 22 genera were identified in Nansi Lake, the abundance of diatom ranged from 14.3×104to 663.2×104cells/L. The results showed the obvious seasonal succession of diatom abundance and community in Nansi Lake; Synedra acuswhich represented cool diatom assemblages was the dominant diatom in spring and winter, while Cyclotella comta which represented warm diatom assemblages was dominant diatom species in summer and autumn; nitrogen and phosphorus nutrients, pH and temperature were main environmental factors affecting diatom community in Nansi Lake.(2) A total number of 52 diatom species belonging to 25 generawere identified in Dongping Lake. The abundance of diatom ranged from 11.2×104～1040.0×104cells/L.Synedra, Cyclotellaand Fragilaria were main diatom genera in Dongping Lake. Nitrogen and phosphorus nutrients and temperature were main environmental factors affecting diatom community in Dongping Lake.(3) The diatom community compositions in Nansi Lake and Dongping Lake aresimilar, the biggest difference of diatom community is the succession in diatom dominant species. In Nansi Lake, the dominant diatom species wascool diatom assemblagesSynedra in spring and winter andwarm diatom assemblagesCyclotella sppin summer and winter.In Dongping Lake, the dominant diatom species were Cyclotellaand Fragilaria. The difference of temperature, water quality and eutrophication in two lakes may be the main reasons causing the difference of diatom community. The average water temperature in Nansi Lake is higher than Dongping Lake, which make the succession of cool and warm diatom assemblages in Nansi Lake is more obvious than Dongping Lake. The water quality and trophic status in Nansi Lake is more serious than Dongping Lake, which provide advantages for the growth of Cyclotellawhose toleranceof pollution and nutrient concentration is good.(4) The abundance of planktonic diatom can indicate eutrophication status:in spring and winter, the change rule of diatom abundance and eutrophication status showed an opposite trend in Nansi Lake; in Dongping Lake, when the diatom density increased significantly, the eutrophication status would also increase. TDI is not suitable for the evaluation of eutrophication status in Nansi Lake and Dongping lake.