Species Richness and Community Structure of Pelagic Zooplankton in Tropical Reservoirs, Hainan Island

Abstract

Forty-seven species of zooplankton, including 7 species of copepods, 8 species of cladocerans and 32 species of rotifers, were identified in an investigation of seven reservoirs in Hainan Island in the dry (December 2006) and wet season (May 2007). All species were eurythermal or mesophilic and their communities were dominated by small-sized species. Common crustaceans included Mesocyclops thermocyclopoides, Bosmina fatalis and Bosminopsis deitersi. The rotifers Brachionus forficula and B. falcatus dominated in the early flood season, while Filinia camasecla dominated in the late dry season. Species richness in oligotrophic and oligo-mesotrophic reservoirs was much higher in the wet than in the dry season, but species richness in the eutrophic reservoirs had a reversed seasonality. The total abundance of zooplankton ranged from 124 to 2,966 ind./L, and biomass ranged from 42.9 to 1,212 μg/L. Abundance of B. fatalis and Diaphanosoma dubium was positively related to that of most species, and Thermocyclops taihokuensis and M. thermocyclopoides were weakly but negatively related to the Cladoceran species. This weak interspecific correlation indicates that other factors such as fish predation affected the coexistence of zooplankton species.