Responses of zooplankton community to environmental factors and phytoplankton biomass in Lake Nansihu,China

Seasonal variations of zooplankton community structure and their relationships with both environmental factors and phytoplankton biomass are investigated in lake nansihu. a total of 76 zooplankton species were identifed in the lake,including 17 protozoa,36 rotifera,12 cladocera and 11 copepods species,respectively. zooplankton species richness changed slightly in the four seasons but varied a lot in different positions. protozoa was absolutely dominated in zooplankton abundance and its mean value ranged from 2710.2 ind./l in winter to 4259.5 ind./l in spring. annual average biomasses of protozoa,rotifera,cladocera and copepods were 0.13 mg/l,0.11 mg/l,0.63 mg/l and 0.34 mg/l,respectively. the lowest values of zooplankton species richness,abundance and biomass appeared at the site which provides the maximum concentrations of nutrients. zooplankton communities were more correlated to phytoplankton community biomass than environmental factors. results of canonical correspondence analysis (cca) revealed that water temperature,secchi disk depth (sd),total phosphorus and phytoplankton biomass were the most signifcant factors that influenced zooplankton. strong correlations between sd and brachionus leydigi,chrysophyta and diaphanosoma leuchtenbergianum,cryptophyta and theopilium,ascomorpha ovalis,hexarthra mira were observed during the cca. these zooplankton species may be used as indicators of relevant variables. results in this research are very useful in guaranteeing ecological security in lake nansihu. © 2017 zoological society of pakistan.