中文摘要：

于2009年7月23日-9月12日（共8周）研究了广东省大沙河水库湖泊区表层5 m水柱浮游植物群落结构和演替过程及其环境影响因子. 降雨明显分为二个阶段，前4周降雨丰富，后4周降雨稀少；水体的透明度与水温也相应地分为二个阶段，但营养盐水平没有明显的变化. 平均N/P为33，而可溶解磷浓度很低，说明浮游植物的生长受磷的限制较为强烈. 浮游植物种类分析中共检到藻类64种，生物量变化为0.95-2.03 mg L^-1，主要由绿藻、甲藻和蓝藻组成. 1-5周浮游植物的总生物量变化较大，后3周总生物量变化相对较小. 在整个采样期间，光角角星鼓藻（Staurastrum muticum）为第一优势种，弯曲角星鼓藻藻（Staurastrum inflexum）为第二优势种（二者约占总生物量的70%）；在1-5周第三个优势种的种类和生物量有较大的变化，6-8周第三优势种为飞燕角甲藻（Ceratium hirundinella）且前3个优势种的组成和生物量较稳定（共占到总生物量的80%以上），群落结构处于稳态平衡状态. 降雨带来的干扰是影响浮游植物群落稳态平衡的主要因子. 当降雨的干扰结束后，浮游植物之间通过1周左右的竞争，浮游植物群落达到稳态平衡. 图7 表3 参23

英文摘要：

Community structures and succession of phytoplankton in a upper water column （5 m） and their factors were investigated in a lacustrine zone of the Dashahe Reservoir of southern China. The investigation lasted 8 weeks from July 23 to September 12, 2009. Precipitation was high in the first four weeks （the first stage） and much low in the last four weeks （the second stage）. Except for the nutrients, external factors such as water transparency and temperature showed a stage variation between two stages. The high average N/P mass ratio of 33 and low concentration of dissolved phosphorus indicated the growth of phytoplankton was strongly limited by phosphorus. Altogether, 64 phytoplankton species were observed during the sampling period. Total phytoplankton biomass ranged from 0.95 to 2.03 mg L^-1, and mainly contributed by Chlorophyta, Pyrrophyta and Cyanobacteria. The phytoplankton biomass fluctuated considerably in the first five weeks, and became stable in the last three weeks. Staurastrum muticum and Staurastrum inflexum were the first and second dominant species, respectively, and contributed to 70% of total biomass throughout the sampling period. The third dominant species frequently changed at the first stage. However, Ceratium hirundinella was consistently the third dominant species at the second stage. The first three dominant species accounted for more than 80% of total biomass in the last three weeks, implying a steady-state phytoplankton community. The precipitation was the critical external stress disturbing phytoplankton assemblages at the first stage. When this external stress disappeared, phytoplankton community evolved to a steady state through inter-specific competition over one week. Fig 7, Tab 3, Ref 23