2007年和2013年夏季（7月）在大兴凯湖（中国一侧）9个采样点调查了沿岸带浮游植物的种类、丰度、生物量和多样性指数等群落动态变化特征。结果显示：2007年夏季鉴定出浮游植物6门55种及其变种，以硅藻和绿藻为主，分别占38％和35％；2013年夏季鉴定出浮游植物4门39种及其变种，以绿藻为主，占44％，与2007年相比较，藻类种数减少了16种。浮游植物数量明显下降，与大兴凯湖旅游业发展、农田废水排放导致的污染加剧有关。优势种从2007年的8种、以硅藻为主减少到2013年的5种、以蓝藻和绿藻为主，说明水体有富营养化的倾向。2013年浮游植物的丰度与生物量均小于2007年，这与2013年的洪水相关。从1#采样点到9#采样点浮游植物的多样性指数依次减少；2013年Shannon-Weaver多样性指数和Margalef丰富度指数均比2007年减小；而Pielou均匀度指数却比2007大，即受人为干扰少的区域多样性指数高于人类活动频繁的地区。%The dynamics features of phytoplankton including phytoplankton species composition, abundance, biomass and distribution and changes were studied in 9 sampling sites in Daxingkai Lak in summer of 2007 and 2013. A total of 55 phytoplankton species and variants in six phyla were identified in summer of 2007, the predominant Bacillariophyceae accounting for 38%and Chlorophyta rep-resenting 35%. However, a total of 39 phytoplankton species and variants in four phyla were observed in summer of 2013,reduced by 16 species and the predominant Chlorophyta accounting for 44%compared to those in 2007. The significant decrease in the phyto-plankton abundance was attributed to pollution in Daxingkai Lake derived from development of tourism and waste-water discharges. The dominant phytoplankton species were reduced from 8 species, predominant diatoms, in 2007 to 5 species, majority of Cyanobacte-ria and Chlorella, in 2013, indicating that there was eutrophication trend. There were less abundance and biomass in 2013 than those in 2007, being involved in the flood. The diversity indexes were shown to be reduced from the 1st sampling site to the 9th of sampling site in turn;the diversity indexes of Shannon-Weaver and Margalef in 2007 were found less than those in 2013. The diversity index of Pielou, however, was higher in 2013 more than in 2007, showing that the phytoplankton diversity index was significantly higher in the undisturbed area in Xiaoxingkai Lake than in the heavy human activity area in Daxingkai Lake.
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