Study on meta-zooplankton community structure of Dianshan Lake

The investigation of the community structure of zooplankton in Dianshan Lake was undertaken monthly during October 2008 to October 2009,including species composition,standing crop dynamics and diversities.A total of 80 metazooplanton species including 46 Rotifera(58%),21 Cladocera(26%) and 13 Copepoda(16%) were encountered.The dominant species were five species of rotifera(Keratella cochlearis,Keratella quadrata,Keratella valga,Brachionus calyciflorus and Brachionus diversicornis),three species of copepod(Microcyclops leuckarti,Sinocalanus dorrii and Schmackeria forbesi) and two other species of cladocera which showed a trend of miniaturization(Bosmina longirostris,Brachionus coregoni and Moina micrura).The zooplankton mean density was 356±334 ind./L and ranged from 52 ind./L in May 2009 to 1260 ind./L in December 2008,and the zooplankton average biomass was 12.67±12.53 mg/L,with the highest value in July 2009 and lowest in December 2008,which was 40.85 mg/L and 1.45 mg/L respectively.Regarding the distribution of the sampling sites,the highest values of the yearly mean density and biomass both appearred in Site 11,and the lowest density in Site 9 with the lowestbiomass in Site 7,respectively.The value of Shannon-Wiener index(H) in Dianshan Lake fluctuated between 0.841 and 2.187,with 1.718 as average.Upon the evaluation of biological diversity index,the water quality of Dianshan Lake could be regarded as α mesosaprobity according to the results analysis.