中文摘要：

三角湖是长江中下游地区典型的小型城市湖泊，近年来其富营养化趋势明显。2014年7月至2015年6月对湖中浮游甲壳动物群落及其影响因子进行了调查，旨在为湖泊污染防治和生态修复提供依据。在三角湖共采集浮游甲壳动物9科17属22种。浮游甲壳动物全年平均密度为（3．7±3．6）ind／L，各月密度变化范围为0．6～13．1ind／L，夏季和秋季密度较低，密度峰值出现在2月。浮游甲壳动物全年大部分时间（5、6月除外）以桡足类及无节幼体占优势，其比例为55．2％～95．4％。浮游甲壳动物物种丰富度变化范围为6～15，平均值为10±3，夏季浮游甲壳动物物种丰富度较低。浮游甲壳动物群落Simpson指数变化范围为0．76～0．90，平均值为0．80±0．04。Pearson相关分析表明，浮游甲壳动物总密度与水深呈显著负相关（r=-0．636，P〈0．05，n=11），显示季节性的水位波动影响浮游甲壳动物密度。典范对应分析（CCA）显示，水温和透明度是影响浮游甲壳动物物种组成季节变化的主要环境因子（P〈0．05）。高密度的鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys nobilis）放养引起的摄食压力可能是三角湖浮游甲壳动物密度较低的主要原因之一。

英文摘要：

Sanjiao Lake is a representative small urban lake in the middle and upper reaches of the Yangtze River. Eutrophication has became a problem for this lake recent years. In order to understand the seasonal community structure of planktonic crustacean and environmental variables, we made a monthly survey in Sanjiao Lake from July 2014 to June 2015 （Fig. 1） to provide a basis for managing eutrophication and providing supports for the ecological restoration efforts. We got the following data： water temperature varied seasonally 10℃ in winter and 28℃ in summer; sechi disk depth 0.27 to 0.72 m; total nitrogen and total phosphorous 1.50 to 3.34 and from 0.07 to 0.58, respectively （Table 1）. We identified a total of 22 species, belonging to 17 genera and 9 families of planktonic crustacean from the seasonal samples. The community included 13 species in Cladocera and 9 species in Copepoda （Table 2）. The species composition showed a light similarity between summer and autumn or winter with Jaccard index ranging from 0.45 to 0.50, and a medium similarity among other seasons with Jaecard index ranging from 0.60 to 0.72 （Table 3）. The density of planktonic crustacean ranged from 0.6 to 13.1 ind/L with an average density of 3.7 ± 3.6 ind/L. The lower density occurred in summer and autumn, while the peak was in February. Copepoda and nauplii dominated the community in most months except May and June, accounting for 55.2% - 95.4% of the total density （Fig. 2）. The dominant species were Cyclops vicinus, Microcyclops leuckarti, Moina irrasa, Microclops varicaricans, M. rectirostris, Diaphanosoma leuchtenbergianum and Bosmina longirostris （Fig. 3）. Species richness of planktonic crustacean ranged from 6 to 15, with an average of 10 a： 3. Higher species richness occurred from late autumn to spring, while the lower value occurred in summer. Simpson index of the community ranged from 0.76 to 0.90, with an average of 0.80 ± 0.04 （Fig. 4）. Pearson correlation analysis showed that the total density of