Study On The Zooplankton Community In The Changjiang River Estuary And Its Adjacent Waters

The study of zooplankton was conducted on two cruise of investigation for the Changjiang River Estuary and adjacent sea area in Jun.2003 and Jun.2006. Zooplankton composition, abundance and dominant species in the waters were studied. The biomass and productivity and their distribution were investigated. The zooplankton community structure and biodiversity were analyzed through multivariate analysis method. The correlations between zooplankton community and envionmental factors were also detected. The research can provide fundamental information for the long-term monitoring of zooplankton ecology in the Changjiang River Estuary and adjacent sea area.A total of 417 zooplankton species (including 34 pelagic larvae) were identified during two surveys. The adult zooplankton mainly belong to Protozoa, Cnidaria, Ctenophora, Annelida, Mollusca, Arthropoda, Chaetognatha and Urochordata, respectively. Crustacea and Cnidaria were the most two abundant components among these identified groups.The species number of pelagic crustacea represented above 50% of total species richness and Copepoda were the most important component.During the cruise of Jun.2003,the mean abundance of the investigated aera was 323.650 ind/m3. The peak value area inhabited each side of the Hangzhou Bay mouth. In Jun.2006, the zooplankton abundance was greater in the north or in the east than in the south or in the west. The mean abundance was 864.760 ind/m3. Calanus sinicus was the most important dominant species in the studied waters.In Jun.2003, the biomass was higher in the south than in the north. The mean zooplankton biomass and productivity of the studied waters was 44.018 mgC/m3 and 2.023 mgC/m3.d, respectively. The peak value area lay in the northeast part of Zhejiang Province offshore waters.The dPc′/Bc value ranged from 0.023 to 0.075, and the mean value was 0.049; In Jun.2006, the mean biomass and productivity of the studied waters was 62.141 mgC/m3 and 3.240 mgC/m3.d, respectively. The peak value area lay in the northeast part of the Zhoushan archipelago and the northeast part of the tested aera. The dPc′/Bc value ranged from 0.032 to 0.087, and the mean value was 0.057. Pearson correlation analysis indicated that dPc′/Bc was significantly correlated to temperature.According to the species composition and abundance, five assemblages or communities were differentiated for the zooplankton by using the method of cluster analysis. CommunityⅠwas a freshwater community, dominated with Sinocalanus dorrii ,S. sinensis et al; CommunityⅡbelong to the central water of the Yellow Sea community, dominated with Calanus sinicus, Corycaeus affinis, C. dahli, Sagitta sinica; CommunityⅢlay in the neighborhood of the Changjiang River mouth, dominated with Nemopsis bachei, Labidocera euchaeta, Schmackeria poplesia et al; CommunityⅣwas dominated with C. sinicus, S. sinica et al; CommunityⅤwas dominated with Evadne tergestina, C. sinicus, Euchaeta plana, E. concinna and S. sinica et al. Salinity was the primary abiotic factor which influence the zooplankton distribution and abundance in the surveyed waters.The zooplankton species diversity in the surveyed waters was quite high. In Jun.2003, the mean Shannon-Weiner Diversity, Pielou′s evenness and Margalef species richness were 2.53, 0.53 and 5.47;And in Jun.2006, the values were 2.79, 0.49 and 9.57, respectively.