中文摘要：

2008年12月三峡水库第一次试验性蓄水至172.8 m后,开县老县城区域被淹没呈水库特征,对蓄水后开县消落区水域水生生物生态及水体营养状态的研究目前还鲜见报道.为了解172.8 m水位后开县消落区水域水环境的现状及藻类群落结构的变化,于2009年1月和2009年12月冬季蓄水期间2次对包括汉丰湖在内的开县消落区水域4个样点藻类组成、数量和生物量的分布及变化情况进行了跟踪观测,初步分析了浮游植物种群结构的变化趋势,并从生物角度评估了水域的水质营养状况.结果表明,2次采样共鉴定出浮游植物6门37属69种（含变种）,优势种群均为甲藻和隐藻,2009年12月藻类细胞密度和生物量低于2009年1月.藻类种群结构和污染指示种评价结果显示,冬季蓄水期间开县消落区各采样断面的营养水平属于中-富营养类型.多样性分析的结果表明开县消落区水域冬季蓄水期间处于中污染状态.

英文摘要：

The old town area of Kaixian county was flooded and showed reservoir characteristics after the water level of Three Gorges Reservoir got 172.8 m in December 2008.The aquatic ecology and nutritional status of Kaixian drawdown area after water storage are still rarely reported.To understand the current water environment and changes in algal community structure of Kaixian drawdown area after 172.8 m water level,the algal composition,abundance,biomass distribution and changes of its sampling spots including Hanfeng Lake were observed twice during winter storage period in January and December 2009.The trends in phytoplankton community structure were analyzed and the water quality assessment of nutritional status was carried out.The results indicated that 6 phylums,37 genera,69 species of phytoplankton in total were identified in the two sampling,and the dominant species were Dinophyta and Cryptophyta.The cell density and biomass in December 2009 were lower than those in January 2009.The evaluation results of algal population structure and pollution indicators showed that the nutrition level of Kaixian drawdown area during the winter storage period was mesotrophic to eutrophic type,while diversity analysis result indicated moderate pollution.