大纵湖浮游植物群落特征及其与环境因子的关系

里下河腹地位于江淮两大水系交融地带，人类活动严重影响区域水生态环境。鉴于浮游植物群落结构及多样性可作为水环境变化重要指示生物，于2015-2017年对里下河腹地典型湖泊大纵湖浮游植物群落结构及环境因子进行逐月采样调查，分别采用藻类生物学指标和综合营养指数对大纵湖营养状态进行综合评价，并且基于相关性分析法，探讨浮游植物与水环境因子的响应关系。结果显示，大纵湖在调查期间共鉴定出浮游植物7门、123种，以绿藻、硅藻、蓝藻为主，分别为50、35、18种，占总种数的40.65%、28.46%、14.63%。全湖各采样点浮游植物的平均丰度为3.70×106 ~6.25×106 个/L；空间上略有差异，夏季藻类丰度较高，冬季最低。大纵湖各个采样点浮游植物优势种基本相同，共8种。浮游植物物种多样性指数和均匀度年均值分别为2.74和0.78，表明大纵湖处于轻-中度污染状态。综合营养指数显示，大纵湖处于轻度富营养状态，两者结果基本一致。相关性分析表明，水温（T）、透明度（SD）、浊度（TUB）和总氮（TN）是影响大纵湖浮游植物群落结构的主要水质指标。

Phytoplankton Community Characteristics and Its Relationship with Environmental Factors in Dazong Lake

Lixiahe District, with a well-developed river/lake system, is affected by the Yangtze and Huaihe Rivers and negatively impacted by human activities. The phytoplankton community provides an important indicator of change in aquatic ecosystems. In this study, Dazong Lake, a typical shallow lake in the Lixiahe District, was selected for a study case, and the structure of phytoplankton community, and associated environmental factors, in Dazong Lake were analyzed, focusing on community composition, dominant species, abundance, diversity and spatiotemporal variations. Meanwhile, algal biological indices and the comprehensive trophic level index were used to assess the trophic status of Dazong Lake. The study was based on monthly phytoplankton surveys and water quality monitoring at three sites from September 2015 to August 2017. A total of 123 phytoplankton species from seven classes were identified, with dominance by Chlorophyta (50 species), Bacillariophyta (35 species) and Cyanophyta (18 species), accounting for 40.65%, 28.46% and 14.63% of the total species, respectively. There were no differences in the eight dominant species among the three sampling sites, but spatiotemporal variations in phytoplankton community composition were significant. The highest species richness occurred in summer and at sample site No.1, and the lowest was in winter with no differences between sites. The average phytoplankton cell abundance was in the range of 3.70×106-6.25×106 cells/L, with small differences among sites. Temporally, there was marked seasonal fluctuation, with the highest cell densities occurring in the summer and the lowest in winter. Phytoplankton community diversity and evenness indices were 2.74 and 0.78, respectively, indicating that Dazong Lake was in a light to moderate pollution condition. The comprehensive trophic level index (TLI) of Dazong Lake was in the range of 50-60, indicating slightly eutrophic conditions, which is consistent with algal indicators. Correlation analysis of phytoplankton community characteristics with water quality parameters showed that water temperature, transparency, turbidity and total nitrogen were the primary factors affecting phytoplankton community structure in Dazong Lake.