Study On The Trophic Structure And The Biomagnification Of The Heavy Metal In The Polyculture Pond

1.Study on the food web of the poly culture pond using stable isotope analysisThe food web in the polyculture pond in Rongcheng Jinghai Bay were investigated between October 2008 and July 2009. Among primary producers, the values of stable carbon isotopeδ13C and nitrogen isotopeδ15N both were ranked as follows:macro algae>STOM>SSOM>SPOM. Theδ13C values of SPOM was significantly positive with the aquatic Chl a during the year. The mean values ofδ13C andδ15N of zooplankton were -18.1±1.22 and 9.56±0.63, respectively. Theδ13C values of invertebrates ranged from -20.34±0.12 to-15.33±0.1, as for theδ15N values, the range was 10.79±0.24-14.54±0.18. The meanδ13C value of fish was -17.81±0.8, and theδ15N values, which ranged from 12.59±0.08 to 16.88±0.35, were more variable than that ofδ13C. Apparent overlap inδ13C values and stepwise enrichment inδ15N values were observed throughout the food web. The 15N enrichment factor was 3.8%o in the polyculture pond and theδ15N values indicated that the pond consisted of 3 trophic levels.2.Study on the effect of jellyfish (Rhopilema esculentum Kishinouye) farming activity on the aquatic, seston and sediment nutrientsTo study the effects of jellyfish (Rhopilema esculentum Kishinouye) farming activities on the sediment nutrients, an experimental station within the farming pond and a reference station adjacent to the farming zone were set in JingHai Bay mariculture zone and samples were collected from both stations between May 2009 and September 2009. In July 2009, when the jellyfish were extensively cultured, the Chi a and POM at the experimental station was significantly higher than that at reference station due to the prey of zooplankton by jellyfish. Perturbed by swimming activity and biodeposition of jellyfish, the NH4-N and NO3-N of sediment and sedimentation rate at the experimental station were significantly higher than those at the reference station; The Chi a and TOM of sediment and seston at the experimental station were significantly lower than those at the reference station. 3.Study on the effect of jellyfish (Rhopilema esculentum Kishinouye) farming activity on the structure of macrobenthic communityTo study the effects of jellyfish (Rhopilema esculentum Kishinouye) farming activities on the structure of macrobenthic community, an experimental station within the farming pond and a reference station adjacent to the farming zone were set in JingHai Bay mariculture zone and samples were collected from both stations between May 2009 and September 2009. The macrobenthos (>0.5mm) presented in the sediment were sampled, identified and enumerated. Shannon-Wiener's diversity index (H') and Pielou's evenness index (J) increased significantly with the cultivation of jellyfish at experimental station in July 2009 and the two indexes were significantly higher than those at reference station. Analysis of similarity for abundance of macrobenthos revealed that the similarity of macrobenthic community between experimental station and reference station was 90% in May 2009 and was approximately 50% in July and September 2009. The similarity of abundance of macrobenthos for both of the experimental station and reference station between July 2009 and September 2009 were approximately 70%. The W values of Abundance-biomass-comparison plots of each sampling month were 0.01,0.308 and-0.128 for experimental station and 0.015,0.03 and 0.109 for reference station. The results of ABC plots were consistent with the variation of the Shannon-Wiener's diversity index. Analysis of correlations showed that the Shannon-Wiener's diversity index (H') was remarkably positively correlated with Pielou's evenness index (J). Both the Shannon-Wiener's diversity index (H') and Pielou's evenness index (J) had negative correlations with the TOM and positive correlations with SR. The TOM of sediment was negatively correlated with sedimentation rate.4.Study on the effect of jellyfish(Rhopilema esculentum Kishinouye) farming activity on the particulate and sediment organic matter by the stable isotope analysisTo study the effects of jellyfish (Rhopilema esculentum Kishinouye) farming activities on the pond ecosystem, an experimental station within the farming pond and a reference station adjacent to the farming zone were set in JingHai Bay mariculture zone and samples were collected from both stations between May 2009 and September 2009 to compare the spatio-temporal changes in the stable isotope carbon and nitrogen isotope of particulate organic matter (POM) and sediment organic matter (SOM). During the three sampling months, significant differences ofδ13C andδ15N values in the POM and SOM at both two stations were observed. In July 2009, when the jellyfish was extensively cultured,δ13C values of POM at experimental station were significantly higher than that at reference station. Both theδ13C values andδ15N values of SOM at the experimental station were signigicantly lower than those at the reference station. Theδ13C values of the POM and SOM were significantly positively correlated with aquatic Chl a and sediment Chl a, respectively. Theδ15N values of POM were significantly negatively correlated with the sediment NO3-N.5.The study on the accumulation of heavy metals (Hg, Cu, Pb, Zn) in the main species in the polyculture pondThe heavy metal amounts of Hg, Cu, Pb and Zn in the main species including 11 kinds of invertebrates and 11 kinds of fishes were measured in the polyculture pond in Rongcheng Jinghai Bay aquaculture zone. The results showed that the heavy metal amounts accumulated in the marine species ranked as follows:Zn>Cu>Pb>Hg. The bivalves and cephalopods contained the highest heavy metal, followed by echinoderms and crustaceans. The accumulative ability for the fishes was the weakest. The different heavy metals accumulated in different kinds of species were ranked as follow:Hg: echinoderm> bivalve≈cephalopod> fish> crustacean Cu:bivalve> cephalopod> crustacean> echinoderm> fish; Pb:cephalopod> bivalve≈echinoderm> fish> crustacean; Zn:cephalopod> bivalve> crustacean> echinoderm> fish. The Ostrea Plicatula, accumulated highest all heavy metals except for Pb, could be used as an indicator for the heavy metal pollutants.