The zooplankton community structures at 11 sampling sites in the mainstream of Huaihe River were investigated in March, June, September and December of 2011. A total of 206 species belonging to 79 genera were identified. Protozoa has 69 species (33. 5% of the total) of 27 genera;Rotifer has 104 species (50. 5%) of 35 genera;Cladocera has 27 species (13. 1%) of 12 genera, and Copepoda has 6 species (2. 9%) of 5 genera. Consequently, the number of species showed a steady decreasing trend from the upper reaches to the lower reaches. The density and biomass of zooplankton were 3527447 ind. /L and 2452 mg/L, respectively. The abundance of protozoa and rotifer were on predominance, and the biomass of rotifer was on predominance. The middle reaches had the highest abundance and biomass of zooplankton. The Shannon-Wiener index and Pielou evenness index of zooplankton in the upper reaches were higher than those in the middle and the lower reaches. This study showed that the water quality of the upper reaches of Huaihe River was in oligotrophic status, while the middle and lower reaches were in mesotrophic sta-tus or eutrophic status. Redundancy analysis showed that temperature, dissolved oxygen and velocity were strongly correlated with the zooplankton community structures.%2011年3、6、9和12月对淮河干流11个采样点的浮游动物群落结构进行调查研究,共检出浮游动物79属206种,其中原生动物27属69种,占浮游动物总物种数的33.5%；轮虫35属104种,占50.5%；枝角类12属27种,占13.1%；桡足类5属6种,占2.9%.总体上看,从上游至下游,浮游动物物种数呈现逐渐减少的趋势.浮游动物的丰度和生物量分别为3527447 ind./L和2452 mg/L,轮虫和原生动物丰度是淮河干流浮游动物丰度的主体,轮虫生物量是淮河干流浮游动物生物量的主体,浮游动物及各类群丰度和生物量均表现为从上游到中游逐渐增高的趋势,而从中游到下游呈现逐渐降低的趋势.上游浮游动物多样性指数和均匀度指数高于中、下游.结果表明：淮河干流上游水质为轻污染,中、下游水质为中污染或重污染.浮游动物群落结构和环境因子的冗余分析表明,水温、溶解氧和流速是与淮河干流浮游动物群落结构相关性较强的环境因子.
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