Studies On The Community Characteristics And Size Spectra Of Zooplankton In The Yellow River Estuary And Its Adjacent Waters In Spring

Based on the zooplankton samples collected with505μm mesh and160μmmesh plankton nets in the Yellow River estuary and its adjacent waters in spring （May.2011）, the zooplankton species composition, dominant species, abundance werestudied and compared, biodiversity and community structure of zooplankton and itsinfluencing factors also were studied by means of multi-variable and bio-environmen-tal analysis. Depending on Sheldon biomass size spectra, the changes of zooplanktontrophic levels with size component were studyed. Depending on the normalizedbiomass size spectra, ecological parameters as energy transfer efficiency betweennutrition levels, community productivity and so on were characterized, and thenormalized biomass size spectra of zooplankton groups were compared.A total of40zooplankton taxa and16pelagic larvae were identified totally, andthey belonged to Ciliophora, Cnidaria, Ctenophora, Mollusca, Arthropoda andChaetognatha.The mean abundance of zooplankton in the samples collected by505μm meshnet was1814.7ind·m^-3. The abundance declined from northwest to southeast in thesurveyed waters.The mean abundance of zooplankton collected with160μm meshnet was100971.2ind·m^-3. The abundance declined from offshore to open warters inthe surveyed waters. The difference came from zooplankton whose ESD between2-4mm and2-1mm. Acartia clausi, Acartia bifilosa, Centropages abdominals, Sagittacrassa, Calanus sinicus, and Brachyura zoea were the dominant species in thesamples collected by505μm mesh net, while Acartia bifilosa, Tintinnopsis sp.,Copepoda nauplii and Oithona similis were the dominant species in the samplescollected by160μm mesh net.The average value of species number, Shannon-Weaner diversity, Margalef species richness and Pielou′s evenness index for the zooplankton collected by505μmmesh net were16,1.60,1.65and0.58respectively, while the values for thezooplankton collected by160μm mesh net were22,0.86,1.31and0.28respectively.Zooplankton biodiversity was higher in the samples collected by505μm mesh netthan that in the samples collected by160μm mesh net accronding to the K-dominancecurves.According to the multivariate analysis, zooplankton communities in two kinds ofnets were the same using the method of cluster analysis. Significant differences ofzooplankton communities were detected in the Yellow River Estuary. Threeassemblages or communities were differentiated for the zooplankton by using themethod of cluster analysis. Group I, with simple species composation, was detected inthe neighborhood of Yellow River Estuary and offshore, as a result of the greatinfluence from the Yellow River discharge and LaiZhou waters. Group II wasinfluenced by the Yellow River discharge and open sea waters. Group III was veryspecial, with only one station, which was located the ford of southern Yellow RiverEstuary.In Sheldon biomass spectra, the diet of zooplankton was changed from herbivo-rous to omnivory and then carnivorous, with the size increasing and the trophic levelrising. In normalized biomass size spectra, the slope was cliffy, suggesting the smallzooplanktons was dominant, and energy transfer efficiency from small zooplanktonsto big ones was low. The intercept was high, suggesting the productivity ofzooplankton communitity was high. The R2was high, suggesting the energy transferefficiency was equal between different trophic levels and the ecosystem was steady. Innormalized biomass size spectra,as to slope, Group II> Group III> Group I, while asto intercept, Group I> Group II> Group III.