The Impact Of Cascade Exploitation On The Phytoplankton In The Upper Reaches Of The Wujiang River

With the development of society and economy, more and more dams were constructed in order to meet the needs of electricity generation, irrigation, flood control and so on. After daming, aquatic ecosystems begin to adapt the changing habitat and evolve from the riverine heterotrophic system (dominated with benthos) to the limnological autotrophic system (dominated with phytoplankton). This dissertation focuses on investigation about the distribution of phytoplankton and their relationship with nutrient elements in the upper reaches of the Wujiang River. The aim of this dissertation is to understand the impact of cascade exploitation on the phytoplankton and to provide a scientific basis for management of water resources.The phytoplankton communities and the water quality were investigated in three phases in 2007:Hongfeng Reservoir, Baihua Reservoir, Xiuwen Reservoir, Zhaixiangkou Reservoir, Hongyan Reservoir, Wujiangdu Reservoir,Suofengying Reservoir, Dongfeng Reservoir, Hongjiadu Reservoir, Yinzidu Reservoir, Puding Reservoir. The analysis of phytoplankton species , community structure, cell density and the mensuration of water quality indexs(WT, SD, pH, DO, TN, NO₂^--N, TP, DOC, COD, K, Na, Ca, Mg , Cl^-, SO₄^2-.).This paper studies correlation between plankton and nutritive elements.The results on the analysis of correlations between cell density and environment factors, the Correlation coefficient are COD (0.786),Chlorophyll-a (0.741),pH (0.423),WT (0.396), DOC (0.377), Mg(0.345),K (0.261),TP (0.207), Cl^-(0.184), DO(0.176), NO₂^--N (0.138). Na (-0.394), SD (-0.386) ,Ca (-0.221), SO₄^2- (-0.134) ,TN (-0.063). COD and Chlorophyll-a is batter remarkable. The results on the analysis of correlations between the biomass and environment factors, The Correlation coefficient are Chlorophyll-a (0.939), pH (0.730) ,COD (0.686), WT (0.593),DOC (0.559),DO(0.514),TP (0.430), Cl^- (0.308), K (0.308), NO₂^--N (0.282), TN (0.100), Mg(0.045), SD (-0.768), Na (-0.557), SO₄^2-(-0.468), Ca (-0.463). The batter remarkable are Chlorophyll-a, pH, COD, WT, DOC, DO, SD, Na.There are 216 species of phytoplankton were identified. They belong to 73 genera 39 families 24 orders 10 classes and 8divisions.Cyanophyta-chlorophyta genre demonstrated in Hongfeng Reservoir. Cyanophyta–chlorophyta–bacillariophyta genre demonstrated in Baihua Reservoir.chlorophyta-Bacillariophyta genre demonstrated in Xiuwen Reservoir, Zaixiangkou Reservoir, Hongyan Reservoir, Hongjiadu Reservoir, Yinzidu Reservoir,Puding Reservoir. Chlorophyta-cyanophyta genre demonstrated in Wujiangdu Reservoir. Bacillariophyta-chlorophyta genre demonstrated in Suofengying Reservoir, Dongfeng Reservoir. To estimate the water quality of reservoir by taking use of phytoplankton cell density and Margalef diversity indices that Hongfeng Reservoir is eutrophic Baihua Reservoir is mesotrophic to light eutrophic.Hongyan Reservoir and Hongjiadu Reservoir are mesotrophic. Light mesotrophic demonstrated in Xiuwen Reservoir, Zaixiangkou Reservoir, Suofengying Reservoir, Dongfeng Reservoir, Hongjiadu Reservoir, Yinzidu Reservoir, Puding Reservoir .Process of cascade exploitation is the rapid increase in phytoplankton, especially Cyanophyta and chlorophyta. The trend of pollution was to eutrophic. Through evolution of different stages of the construction of the reservoir and Reservoir phytoplankton evolution, the trend of pollution was to eutrophic, Bacillariophyta-chlorophyta genre to Cyanophyta and chlorophyta genre in the reservoir.