[Temporal and Spatial Variation of Zooplankton Community Structure and Its Relationship with Environmental Factors in Dianshan Lake, Shanghai].

Dianshan Lake, a subtropical shallow lake, is the largest freshwater body located in Shanghai. To reveal the temporal and spatial variation of zooplankton community structure and its relationships with environmental factors, monthly data of zooplankton and phytoplankton content and associated physicochemical parameters for 2017 were analyzed using multivariate regression trees (MRT) and principal coordinates analysis (PCoA). The results indicated that there were significant seasonal differences in the community structure of zooplankton (<0.05). However, spatial variations were significant only in spring and summer (<0.05). The results indicated that water temperature (WT), chlorophyll-a (Chla), ammonia nitrogen, and cyanobacteria were the key driving factors in the observed spatial and temporal variations in the zooplankton community structure. The MRT analysis illustrated that zooplankton community structure varied strongly across four groups, including spring (13.07℃ ≤ WT<19.57℃), summer (WT ≥ 19.57℃, Chla ≥ 9.03 μg·L), autumn (WT ≥ 19.57℃, Chla<9.03 μg·L), and winter (WT<13.07℃). In addition, three distinct regions were identified by the cluster analysis. The MRT analysis illustrated that the zooplankton community structure was distinct between samples with relatively lower (<1.11 mg·L) and higher concentrations (≥ 1.11 mg·L) of ammonia nitrogen in spring. Furthermore, cyanobacteria were identified as a major stressor on zooplankton in summer. These observations further show that that zooplankton community structure in area I (with a cyanobacterial biomass of ≥ 2.58 mg·L) was significantly different from other regions (with a cyanobacterial biomass of <2.58 mg·L).