Community Structure Characteristics Of Zooplankton In The Ctenopharyngodon Idellus Ponds And Correlations Between Zooplankton And Environment Factors

We investigated6times about the Ctenopharyngodon idellus ponds in May to October2012. The main content of the experiment was investigated the species composition, density, biomass of zooplankton in the ponds. The Correlation analysis, Stepwise regression analysis, Path analysis were used to analysis the zooplankton biomass, density and the environment factors in relation. Using carbon and nitrogen stable isotope to analysis the food web structure and ecosystem trophic level of the ponds. We can know the water quality by the relationship between zooplankton and environment factors to make reasonable breeding plans. The main results are as follows:1. During the experiment,47genera43species of zooplankton were identified, which consisted of20genera and27species for protozoa,23genera and47species for rotifer, two genera and four species for Cladocera, two genera and two species for copepods. The dominant species of zooplankton were protozoa and rotifer, whose numbers added up to92.5%of the total number of species of zooplankton. Through the analysis of dominance,10species were identified to be dominant, which consisted6species for protozoa,4species for rotifer. The dominant species of zooplankton were C.irtus、A. faurei、A.volvox、T.pyriformis、H. grandinella、S. viride、A. fissa、 P. trila、T. pusilla and T. capuina.2. During the experiment, the densities of zooplankton in the ponds were2.27～3.59(×104) ind/L、2.19～4.25(×104) ind/L and3.38～3.49(×104)ind/L, respectively.. The biomasses of zooplankton in the ponds were2.75～7.06mg/L、2.92～5.65mg/L and2.64～6.65mg/L, respectively.3. The Shannon-Wiener indexes of zooplankton were2.22～3.33、2.17～3.03and2.03～2.95in the first, second and third pond, respectively.4. In order to analysis the relationship between the zooplankton and environment factors in the ponds,we used the Correlation analysis,Stepwise regression analysis and Path analysis to explain it. The zooplankton biomass and density have a significant correlation with DO, WT, pH, TP, TN, NO3-N, NO2-N, SD, COD and reactive phosphorus by Pearson correlation analysis. The Stepwise regression analysis revealed that TN, DO, NO3-N play a vital role in zooplankton biomass and density. The Path analysis showed that the environment factors indicate a direct role of zooplankton biomass and density, but also indirect effects on them. Its indirect impact is obvious than direct effects sometimes.5. Stable carbon and nitrogen isotopic were used to investigate food web and trophic level in the ponds. The813C of phytoplankton was closely to suspended matter. The815N of the fishes was significant higher than the food sources. The trophic level of the main consumers were2.5-3.5, the order of rophic level were Aristichthys nobilis> Hypophthalmichthys molitrix> Parabramis pekinensis> Ctenopharyngodon idellus.