香溪河流域梯级水库底栖动物群落比较

对香溪河流域3座梯级水库（古洞口一级水库、古洞口二级水库和三峡水库香溪河库湾）的底栖动物进行了比较生态学研究。运用主成分分析（PCA）对梯级水库的水质进行研究，表明沿着水库的梯度水质逐渐恶化。运用非度量多维标度法（NMS）对梯级水库的底栖动物群落结构进行相似性比较，表明选择水库湖泊区的样点进行梯级水库底栖动物生态学研究具有典型代表性。在物种组成和密度方面，古洞口一级水库和香溪河库湾都是寡毛类占优势，古洞口二级水库是摇蚊幼虫占优势。但3个水库都是耐污种占优势。采用典型对应分析（CCA）解析底栖动物群落结构与环境因子的关系，显示3个水库群落结构的差异主要由浊度造成。用TOC／Turb来表征有机物对浊度的贡献，结果显示古洞口二级水库有机物对浊度的贡献相对较小，因而表明泥沙等无机物对浊度的贡献相对较大。

Comparative on macroinvertebrate communities along a cascade of reservoirs in Xiangxi River Basin

Xiangxi River originates from the Shennongjia Forest region and is the largest tributary in the Hubei portion of the Three-Gorge Reservoir.The hydropower resource is abundant in Xiangxi River,and hydropower stations are usually connected sequentially.A cascade of three reservoirs(Gudongkou Reservoir 1,Gudongkou Reservoir 2 and Xiangxi Bay of the Three-Gorge Reservoir)in Xiangxi River Basin was selected to investigate macroinvertebrate ecology in a reservoir cascade system.Principal Components Analysis(PCA)was applied to analyze the water quality of the three reservoirs.The result implies that the water quality was degrading along the cascade of reservoirs.Non-metric Multidimensional Scaling(NMS)was used to analyze the differences among benthic communities.It indicates that sampling stations located in the lacustrine zone of a reservoir are representative for comparing macroinvertebrate assemblages along a reservoir cascade.Oligochaetes were numerically dominant both in Gudongkou Reservoir 1 and Xiangxi Bay,and chironomids were dominant in Gudongkou Reservoir 2.Similar pattern was also exhibited in species composition.However,the benthic assemblages of the three reservoirs were all dominated by pollution-tolerant taxa in spite of their differences in water quality.Relationship between the community structure and environmental variables was studied by using Canonical Correspondence Analysis(CCA)to determine which variables contribute most to differences in community structure.It discloses that turbidity influenced the benthic assemblages significantly.TOC/Turb was applied to determine the influence of organic matter on turbidity.The ratio of Gudongkou Reservoir 2 was the lowest among the three reservoirs,which implicates that the influence of organic matter on turbidity was smaller in Gudongkou Reservoir 2 than those in the other two reservoirs.This suggests that inorganic matter such as suspended silt and clay grains contribute substantially to the turbidity of Gudongkou Reservoir 2.