Reaserch On The Relationship Between Plankton And Environmental Factors Around The Water Head Site Of Shangshan Cui Village In Taihu Lake

Taihu Lake is one of the typical shallow lakes in the middle and lower reaches of Changjiang River. From January to September in 2015, the research on water head site of Shangshan Cui Village includes related physical and chemical indices and the types, the density and the dominant species of plankton. By 3 diversity indices and comprehensive nutritional status index method, the correlation analysis and the simple regression analysis of plankton and environment factors evaluate diversity and eutrophication of the water head site of Shangshan Cui Village.In research, there are 5 phyla and 19 families of phytoplankton, in which the melosira granulata(Ehr.) Ralfs in winter and microcystis in summer are dominant, and the average density of frustule is 35,505,400/L.The Margalef index movement of the water head site of Shangshan Cui Village is between 0.628 and 1.054 and the average is 0.813. The Shannon index movement is between 0.203 and 0.965 and the average is 0.487. The Pielou uniformity movement is between 0.291 and 1.381 and the average is 0.697. The fitting of Shannon and Margalef shows a serious pollution state in Shanghshan Cui Village.Analyze various physical and chemical factors in Shanghan Cui Village and chlorophyll a of phytoplankton the density and the types of frustule to show a positive correlation of density, water temperature and p H and a negative correlation of transparency and dissolved oxygen, meanwhile, a negative correlation of types and p H and a positive correlation of types and dissolved oxygen. Screen and then analyze the correlation factors by simple regression analysis to get a regression equation and find a good fitting degree. There is not a correlation between algal density and nutrient Salts of Phosphorus and Nitrogen. It is possible that there is high eutrophication level in Shangshan Cui Village and it exceeds algae assimilation effect level, so Phosphorus and Nitrogen become never the limiting factor of blue-green algae.In 7 sampling from January and September in 2015, there are 19 families of phytoplankton, among which 10 families of rotifer species, 5 families of cladocera and 4 families of copepods; brachionuscalyciflorus, bosmina coregoni macrocopa and the narrow abdomen of cyclops are the dominant. From January and September, the density movement is between 163ind×L-1 and 962ind×L-1, and the average is 524 ind×L-1. Rotifer in winter takes the absolute advantage and the cladocera takes a rising position from winter to summer and in summer the cladocera is the dominant.There is an obvious negative correlation between the quantity of rotifer and p H, alga density and quantity of copepods. And there is an obvious positive correlation between the quantity of cladocera and water temperature, density and quantity of copepods and there is an obvious negative correlation between the quantity of cladocera and transparency. The quantity of copepods has an obvious positive correlation with water temperature, p H, alga density and the quantity of cladocera and it has an obvious negative correlation with transparency and the quantity of rotifer. From winter to summer, the cladocera in the water area of Shangshan Cui Village has a tread of miniaturization and the bosmina family takes the absolute advantage in summer.From January to September, the movement of the comprehensive nutrient index in Shangshan Cui Village is between 49.4 and 60.5. When in winter and early spring from January to March, it is at medium nutrient level; when it is in April, the index has become rising and achieves light eutrophication level and until summer, from August to September, it achieves medium eutrophication level. According to the average index from January to September, it could evaluate that the water head site in Shangshan Cui Village is always at light eutrophication level. The Shangshan Cui Village belongs to Algae-Type Zone; the exchange of nutritive salt between substratum and water, the large quantity of chlorophyll a because of mass reproduction of algae, and the low transparency, all these 3 factors show that the Taihu Lake achieves eutrophication level. The eutrophication status in the water head site in Shangshan Cui is caused by the biotic factor and environmental factor.