Ecological distribution characteristics of zooplankton in Yangtze River estuary in spring and summer during 2007-2008

In this study,the ecological characteristics of zooplankton in Yangtze River estuary were described and its relationship to the environmental factors was analyzed.Sampling was carried out in May and August between 2007 and 2008.Results showed that the biomass of zooplankton in August was higher than that in May,increasing gradually from coastal region towards offshore.In May,Tortanus vermiculus and Labidocera euchaeta were both the dominant species,which spread in estuarine waters and littoral waters.In August,the dominant species in estuarine waters and littoral waters were changed to Centropages dorsispinatus and Acartia pacifica.In offshore waters,Sagitta enflata was also one of the dominant species in August.Calanus sinicus,the only species occurred in all 4 oceanographic censuses was the most important dominant species in nearshore waters out of the Yangtze River estuary.The distribution pattern of the species number and diversity index showed a tendency of increasing gradually from coastal region to offshore waters.Salinity,temperature and Calanus sinicus were the important factors affecting the distribution of zooplankton in the waters near the Yangtze River estuary.