ZOOPLANKTON COMMUNITY STRUCTURE IN YANGTZE RIVER ESTUARY AND ADJACENT SEA AREA IN SUMMER 2006

Zooplankton was studied on a cruise ship in the Yangtze River Estuary and adjacent sea area in Jun 2006. Water zooplankton composition,abundance and dominant species were studied. Zooplankton community structure and its influencing factors were studied with multivariate analysis based on sample data and environmental parameters. The work provides fundamental information for long-term monitoring of zooplankton ecology in the Yangtze River Estuary and adjacent sea area. A total of 322 zooplankton species (including 27 pelagic larvae) were identified as a result of the survey. Crustacea and Cnidaria were the two most abundant components among the identified groups. The number of species of pelagic Crustacea represented more than 50% of total species richness,Copepoda was the most important component. Calanus sinicus was the dominant species in the waters. According to species composition and abundance,five assemblages or communities were differentiated for the zooplankton by cluster analysis. Community Ⅰ was a freshwater community,dominated by Sinocalanus dorrii,Schmackeria forbesi; Community Ⅱ lay in the neighborhood of the Yangtze River mouth,dominated by Schmackeria poplesia,Labidocera euchaeta,Tortanus vermiculus; Community Ⅲ belong to the central water of the Yellow Sea community,dominated by C. sinicus,Corycaeus affinis,C. dahli,Sagitta nagae; Community Ⅳ was dominated by C. sinicus,Euchaeta plana,S. nagae,Doliolum denticulatum; Community Ⅴ was dominated by Evadne tergestina,Euconchoecia aculeata,C. sinicus,E. plana,E. concinna,Dolioetta gegenbauri,D. denticulatum. Salinity was the primary abiotic factor influencing zooplankton distribution and abundance in the surveyed waters.