Research Of The Phytoplankton Composition Variety And Eutrophication Features Of Weining Caohai, Guizhou

By the investigation of water quality and phytoplankton community inCaohai lake, estimated the eutrophication degree, and discussed the relationamong eutrophication factors in Caohai lake. Investigated the water physical and chemical indexes of Caohai lake fromJanuary 2004 to January 2005. The average water temperature (WT) is 14.4 ℃ ,not over 20 ℃ except for in summer; Transparence (Tran.) range from 0.23m to1.60m, The comparation of transparence and water-deep (WD) is 0.91; AveragepH is 6.95, the water is weak acidity in winter, and most of time is weakalkalescence; Electric conductivity rate (EC) is 18.88S.m^-1, dissolve salt (DS) is11.89 mg.L^-1; dissolve oxygen (DO) is 6.88 mg.L^-1; The chemistry oxygendepletion (COD) is 20mg.L^-1; Total nitrogens (TN) is 1.280 mg.L^-1, totalphosphorus (TP) is 0.0485 mg.L^-1, the comparison of nitrogen and phosphorus(N/P) is 26.39.The results demonstrated that the water quality of Caohai isbetween Ⅱand Ⅲ , and contains higher DS, serious organism pollution, and theCaohai is P-limits lake. Investigated phytoplankton community in Caohai lake.There are 390species of phytoplankton. They consist of 7 phyla, 10 classes, 23 orders, 41families, and 96 genera. Most of them is belong to Charophyta, Cyanophyta andBacillariophyta. There are 60 species of phytoplankton appear in a year; 105species of phytoplankton are pollution indicator, and many of them are α – psand β – ps; most of dominant species are pollution indicator. The averagedensity of phytoplankton is 5.094×106n.L-1;the biomass is 4.918mg.L-1;andChlorophyll-a is 4.79mg.m-3. Evaluated eutrophication degree by bio-indexes: The Charophyta index is0.4; Synthetic index is 3.7; Margalef index is 3.493; Shannon- Weaver index is1.414; Pielous evenness index is 0.237; TLI(Σ) index is 42.94.The evaluationresult of each index difference. It indicated that evaluted eutrophication degreeby single factor of Caohai exists limitation. And Caohai reaches moderateeutrophication level, the partial area of Caohai is most eutrophication level. By the analysis of bivariate and partial correlations: There are saliencepositive correlations between Chl-a and PD,PB and PD, Chl-a and PB,TN andTP,COD and TN, pH and TP,WT and TP,WT and pH, TP and DS, and saliencenegative correlations DO between TP, EC, DS by the analysis of bivariatecorrelations. It indicated that COD is a tie of bio-indexes and phys-chem indexes,the DS is N-ion and P-ion. And there is salience positive correlations betweenChl-a and TP by the analysis of partial correlations, It indicated that the otherindexes had the influence on the correlations of Chl-a and TP.