Zooplankton response to the lake restoration in the drinking-water source in Meiliang Bay of subtropical eutrophic Lake Taihu, China

A 3-year ecological engineering project was carried out from 2003 to 2005 in the drinking water source in Meiliang Bay, Lake Taihu, China. The project area was divided into three zones: Zone C (outside the area), Zone B (pelagic part within the area) and Zone A (littoral part within the area). The community composition, density and biomass of zooplankton were studied as a part in the lake restoration study. Also, the abundance, biomass and composition of fish in the engineering area were annually analyzed in the littoral zone (Zone A). The average density of cladocerans decreased from the outer part to the inner part of the lake, i.e., from Zone C to Zone A, while the average density of copepod did not significantly vary among the 3 zones. The average densities of rotifer and ciliate increased from Zone C to Zone A. RDA analysis indicated that Microcystis biomass more impacted the zooplankton compositions after temperature. In Zone A, many planktivorous fishes, e.g., Coilia nasus, Hemiculter leucisculus, Pseudorasbora parva, dominated the fish community, which caused a marked decrease in the abundance of cladocerans, especially large-sized cladoceran Daphnia galeata and Daphnia obtusa. Our results suggested that both fish predation and other environmental factors such as the Microcystis bloom greatly affected the zooplankton community during the restoration of subtropical eutrophic lakes.