太湖梅梁湾浮游动物群落结构长期变化特征(1997~2017年)

浮游动物作为水体食物链的重要组成部分，在湖泊生态系统中发挥着重要作用.然而，作为水质重要监测指标，由于浮游动物群落结构长期连续监测数据的缺失，导致关于浮游动物群落结构长期变化特征的认识较为缺乏.基于太湖梅梁湾1997~2017年逐月连续监测数据，研究了浮游动物群落结构的长期变化特征，探讨了其与环境因子的关系.结果显示，在此期间，太湖梅梁湾浮游动物丰度和生物量均显著下降（P<0.05）.其中，轮虫和桡足类丰度和生物量均缓慢下降，枝角类丰度处于波动而生物量表现为显著下降（P<0.05）.枝角类生物量对太湖梅梁湾浮游动物生物量的贡献最大.小型的枝角类和桡足类的优势度随着轮虫丰度的降低而增大，浮游动物的平均体型显著减小（P<0.05），浮游动物呈现出小型化演化特征，并潜在减弱对浮游植物的下行效应.此外，浮游动物丰度和生物量在春季呈上升趋势而在秋冬季呈下降趋势，并在9月达到最大值1406.70 ind.·L^-1和25.64 mg·L^-1.而在夏季它们的变化趋势则相反.Pearson相关性分析显示，浮游动物群落结构主要与水体物理特征（碱度、电导率、水深、悬浮物质和水温）、叶绿素a和氮元素密切相关（P<0.05），说明太湖梅梁湾水体富营养化对浮游动物的群落结构具有重要影响.

Long-term Variation Characteristics of Zooplankton Community Structure in Meiliang Bay, Lake Taihu

Zooplankton, as an important part of the water food chain, plays an important role in lake ecosystems. It is an important monitoring indicator for water bodies. However, due to the lack of long-term monitoring data of zooplankton community structure, there is a lack of understanding about its long-term characteristics. Based on monthly monitoring data from 1997 to 2017 of Meiliang Bay in Lake Taihu, the long-term trends of zooplankton community structure and its relation to the environment were examined. The results showed that the abundance and biomass of zooplankton in Meiliang Bay significantly decreased from 1997 to 2017 (P<0.05). In particular, the abundance and biomass of rotifer and copepod slowly declined, and the abundance of cladocerans fluctuated but its biomass presented a significant decreasing trend (P<0.05). The cladocerous biomass contributed the most to the zooplankton biomass in Meiliang Bay. The dominance of smaller cladocerans and copepods increased with decreasing rotifer density, significantly decreasing the average body size of zooplankton (P<0.05). This study indicated that zooplankton were becoming smaller, potentially weakening the top-down control on phytoplankton. In addition, zooplankton abundance and biomass showed an upward trend in spring and decreased in autumn and winter, and reached maximum values of 1406.70 ind.·L^-1 and 25.64 mg·L^-1, respectively, in September. In the summer, their changes were the opposite. Pearson correlation analysis showed that zooplankton community structure was significantly related to water physical characteristics (alkalinity, electrical conductivity, water depth, suspended substance, and water temperature), chlorophyll a, and nitrogen (P<0.05). This indicated that the eutrophication of Meiliang Bay in Lake Taihu had a significant impact on the community structure of zooplankton.