Study On The Community Ecology Of Zooplankton In The Yellow Sea And The East China Sea In Summer And Winter

Study of zooplankton was conducted on two cruises of investigation for the Yellow Sea and the East China Sea in summer 2006 and the next winter. Zooplankton species composition, abundance, biomass and biodiversity were studied, so was the correlation between zooplankton and environmental factors. Zooplankton community structure and its dominant species were analyzed through multivariate analysis method. The purpose of this research is to provide fundamental information for the long-term monitoring of zooplankton ecology in the Yellow Sea and the East China Sea.A total of 584 zooplankton taxa (not including 28 pelagic larvae) were identified during two surveys. The adult zooplankton species belong to Protozoa, Cnidaria, Ctenophora, Annelida, Mollusca, Arthropoda, Chaetognatha and Urochordata, respectively. A new species of Cnidaria was record in winter, which is Nubiella sinica.During summer, the mean abundance value of zooplankton in surveyed waters was 1118.8 ind/m3. The peak value was located in the adjacent sea waters of Changjiang River Estuary and the coastal region of East China Sea. The offshore area of East China Sea and the Yellow Sea had relatively low zooplankton abundance. Zooplankton abundance decreased sharply during winter, the mean value of which was 178.4 ind/m3 only. Distribution of zooplankton abundance in the investigated area was relatively uniform in winter.During summer, the mean biomass of zooplankton in surveyed area was 485.6 mg/m3. The highest zooplankton biomass appeared in the Yellow Sea, while the offshore area of East China Sea had the lowest zooplankton biomass. During winter, the mean biomass of zooplankton in surveyed area was only 94.6 mg/m3. The Yellow Sea also had the highest zooplankton biomass, while the coastal region of East China Sea had the lowest zooplankton biomass. Variation of zooplankton biomass was consistent with abundance in the East China Sea, while the Yellow Sea could have high biomass accompanying with low abundance.Biodiversity of zooplankton in the investigated area was quite high. The mean Shannon-Weaner index value was 2.808 in summer, and 3.536 in winter. The species number, Margalef richness, Pielou's evenness and Shannon-Weaner index of zooplankton were highly correlated with depth, temperature and salinity.During summer, according to the zooplankton species composition and abundance at each station, four groups were distinguished by using the method of cluster analysis.â…°) Yellow Sea Community (Ys). It was influenced by the Yellow Sea warm water, the Coastal Current and the Yellow Sea Cold Water, and was dominated with Calunus sinicus, Sagitta crassa and Euphausia pacifica.â…±) Changjiang Estuary Community (CJs). The freshwater inflow resulted in low salinity, so mesohaline species such as Centropages dorsispinatus and Labidocera euchaeta were more abundance in this community.â…²) East China Sea Coastal Community (ECs). This community located in the coastal region of the East China Sea and the adjacent areas of the Changjiang estuary, and was mainly controlled by the Coastal Current which was characterized with relatively low salinity and high temperature. Neritic species Evadne tergestina was its main dominant species.â…³) East China Sea Mixed-water Community (EMs). It located in the middle part of the East China Sea where the Kuroshio Branch Current mixed with the Coastal Current, resulting in the formation of a hydrographically complex area. Species adapted to high temperature and high salinity such as Undinula vulgaris, Eucalanus subcrassus, Temora tubinata and Lucifer intermudius were in dominance.During winter, zooplankton was also differentiated into four groups.â…°) Yellow Sea Community (Yw). The location and dominant species of Yw had few differences with Ys.â…±) Coastal Community (Cw). This community located in a threadlike coastal region of the Yellow Sea and the East China Sea, and neritic species such as Paracalanus parvus, Oithona similis, Corycaeus affinis and Oikopleura dioica were its dominant species.â…²) East China Sea Mixed-water Community (EMw). Accompanying with the decreasing of temperature and salinity, widely-distributed species including Calunus sinicus, Paracalanus aculeatus, Paracalanus parvus, Oithona plumifera and Sagitta sinica instead of the warm-water species dominated this community in winter.â…³) East China Sea Offshore Community (EOw). This community located in the offshore area of the East China Sea which was mainly influenced by the Krushio. Its dominant species included both widely-distributed species such as Calunus sinicus, Paracalanus aculeatus, Oithona plumifera, Oikopleura longicauda and warm-water species such as Clausocalanus arcuicornis and Oncaea venusta.The abundance and distribution of Paracalanus parvus and Paracalanus aculeatus in our survey were different from the historical investigations. It was the first time to record Oithona plumifera to be the important dominant species in surveyed area. It was also the first time to record a large number of Salpa fusiformis in the middle part of the Yellow Sea. Causing of these changes need more and further studies to explain.