淀山湖水华高发期浮游植物群落变化特征研究

根据2009年5～10月淀山湖浮游植物数量和种类的观测结果,对水华高发季节浮游植物群落组成特点及优势种交替过程进行分析,初步探讨这一时期浮游植物群落特征与环境因子的关系.结果表明,这一时期浮游植物主要由蓝藻和绿藻组成,蓝藻在密度上、绿藻在种类上占优势.水平分布上,西部和西南部的蓝藻密度值和种类数较高.总密度最高峰出现在9月,其值为23.40×107cells.L-1,其中蓝藻数量占90.3%,各样点间总密度差异显著(ANOVA,P<0.05).优势种在调查期间存在明显的交替现象,蓝藻门微囊藻属(Microcystis)藻类逐步成为优势种并形成水华.水温与pH是影响水华发生的重要环境因子,微囊藻受风向影响容易向下风向水域聚集形成水华.淀山湖中部和西部的浮游植物多样性较差,水华暴发时,全湖多样性指数降低,群落结构趋于简单.

Characteristics of Phytoplankton Community Changes in Dianshan Lake During Peak Period of Algal Blooms

Based on the investigation data of phytoplankton in Dianshan Lake from May to October in 2009,the characteristics of phytoplankton community and the dominant species succession are studied. The results show that Cyanophyta and Chlorophta are the main taxa. Cyanophyta is dominant in cell abundance and Chlorophta is dominant in species variety. From the flat distribution, the species variety and density of Cyanophyta are higher in west and southwest. The peak of cell density reaches 23.40×10⁷ cells·L^-1 in September due to the occurrence of cyanobacterial bloom, Cyanophyta account for 90.3 percents, with significant differences in each point (ANOVA, P<0.05). An obvious succession of phytoplankton species is found, Microcystis of Cyanophyta become the dominant taxa and then conglutinated together to form water bloom. Temperature and pH are the main factors that affect the cyanobacterial bloom, and wind direction is an important reason for the horizontal distribution of the bloom-forming Microcystis. The phytoplankton diversity index is poor in central and western sites, diversity index decreases during cyanobacterial bloom and the community structures are simple.