Studies On Community Structure And Biodiversity Of Zooplankton In The Yellow Sea And The East China Sea

The species composition, abundance and biodiversity of zooplankton in the Yellow Sea and the East China Sea were studied based on the samples collected during four cruises in Jun.-Jul.2006, Jan.-Feb.2007, Nov.2007 and Apr.-May 2009. Zooplankton community structure were analyzed through multivariate analysis method. The correlations between zooplankton community and envionmental factors were also discussed. The taxonomic diversity of pelagic copepods in the Yellow Sea and the East China Sea were studied. This is the first time of taxonomic diversity to be used in community ecology of zooplankton in China seas. The major objective of this study is to elucidate zooplankton species composition and distribution on the shelf and to explore the relation of zooplankton community with environment. This research can provide fundamental information for the long-term monitoring of plankton ecology in the Yellow Sea and East China Sea. The main results are as follows:A total of 859 zooplankton taxa and 37 pelagic larvae were identified during 4 surveys. The zooplankton species belong to 8 phyla:Protozoa, Cnidaria, Ctenophora, Annelida, Mollusca, Arthropoda, Chaetognatha and Urochordata. The species number of Crustacea and Cnidaria were most abundant among these identified groups. The species number of pelagic crustacean represented above 50% of total species richness and copepods was the most important component.The abundance of zooplankton in the Yellow Sea and the East China Sea changed dramatically during 4 seasons. Protozoan, copepods and pelagic larvae were the most abundant groups, which greatly controlled the distribution of tatal abundance. In spring, the mean abundance of zooplankton was 5036.9 ind/m3, and the high value area was located in coastal region of Shandong, Zhejiang and Fujian Province and the adjacent waters of Changjiang River Estuary. Protozoan was in great dominance, with mean abundance of 3964.6 ind/m3, followed by copepods (707.6 ind/m3) and pelagic larvae (78.4 ind/m3). In summer, the average abundance of zooplankton was 1118.8 ind/m, and the abundance in the East China Sea was higher than that in the Yellow Sea. The high value area located in coastal area of the East China Sea. The protozoan abundance declined obviously (16.3 ind/m3) during summer. The average abundance of copepods was 443.9 ind/m3, and its spatial distribution was relatively even in suvryed area. Pelagic larvae mainly distributed in the coastal region of Zhejiang and Fujian Province, the adjacent waters of Changjiang River Estuary and in the north of Shandong Peninsula, with mean abundance of 57.4 ind/m3. In autumn, the average abundance of zooplankton was 790.2 ind/m3, and distributed relatively even in suvryed area. The mean abundance of protozoan was 167.9 ind/m3, and copepods was 353.8 ind/m3. Pelagic larvae abundance came to the maximum value (81.8 ind/m3) in the year. Zooplankton abundance decreased sharply during winter (162.3 ind/m3), the highest value presented in the offshore area of the East China Sea. The distribution trend of copepods and pelagic larvae was similar with total abundance, and the average value was 64.8 ind/m3 and 9.3 ind/m3, respectively.There were many different ecological categories in zooplankton community in this region, and each category had its relevant hydrographic factor. The proportion of each category varied following the change of environmental conditions in different seasons, so the zooplankton abundance showed different relationships with environmental factors in 4 seasons.Zooplankton biodiversity was significantly higher in autumn and winter than that in summer and spring, but the spatial distribution pattern was almost the same: Offshore area of the East China Sea> Inshore area of the East China Sea> the Yellow Sea. The species richness decreased gradually with increasing latitude. Especially in the East China Sea, zooplankton biodiversity performed an obvious gradient across the shelf.According to the multivariate analysis, significant differences of zooplankton communities were detected between the Yellow Sea and East China Sea. Communities in the Yellow Sea belong to "temperate fauna", with simple species composation, including Yellow Sea Community (Y) and Yellow Sea Coastal Community (Subei Coastal Community, SC); Communities in the East China Sea belong to "warm-water fauna", including Kuroshio Community (K), East China Sea Mixed-water Community (EM) and East China Sea Coastal Community (EC). Zooplankton community structure was more complex in the East China Sea,3 communities form a cross-shore zonation. Besides, a Changjiang River Estuary Community (CJ) was detected in summer in the neighborhood of Changjiang River delta, as a result of the great influence from Changjiang River discharge. Environment with different oceangraphic features support pelagic fauna with different species compositions. The present study showed a clear relationship between zooplankton assemblages and water masses distributions. The boundaries of the different planktonic communities shift with changes in hydrographic conditions, especially, with changes in the movement of water masses and currents in different seasons.The biodiversity distribution tendencies of pelagic copepods showed different patterns depending on which index was being calculated. Species richness and Shannon-Wiener index were significantly higher in East China Sea, whereas taxonomic distinctness was significantly higher in the Yellow Sea.Based on the present surveys combined with previous studies, the master list of pelagic copepods in the Yellow Sea and the East China Sea were set up, and its hierarchical diversity was analysed. A total of 5 orders,44 families,109 genera and 406 species of pelagic copepods heretofore recorded in the Yellow Sea and East China Sea. The funnel plots with 95% confidence limits for both Average Taxonomic Distinctness (AvTD,⊿+) and Variation in Taxonomic Distinctness (VarTD, A+) and the ellipse plots with 95% probability contours for the joint distribution of AvTD and VarTD of the pelagic copepods master list of the Yellow Sea and East China Sea were established, and the AvTD is 84.3.The AvTD value of each community in different season all fell inside the confidence funnel, which indicated a normal state of community structure. The VarTD value of many stations of Kuroshio Community and East China Sea Mixed-water Community fell above the confidence funnel, indicating a higher than expected variation in distinctness of species pairs.