The Studies On The Food Web Structures Of Northern China Sea By Stable Isotopes Analysis

Based on the analysis of stable isotopes, the food web structures of Northern China Seawere studied. The comprehensive sample preservation and processing methods of marine food web for stable isotopic analysis were given. Basic data of Northern Sea were provided by the study of stable carbon and nitrogen isotope values of the typical algae. In order to provide crucial information on the major sources of organic matter, spatial and temporal variations of carbon and nitrogen stable isotopes in intertidal suspended particulate organic matters and sedimentswere evaluated. According to the variations of813C and815N of intertidal and main nektonic food web in Northern Sea, the food web structre and trophic relationships, and feeding habits among different biolo-gical were explored.The main results are as follows:We suggest that drying is the most suitable method for preserving samples, since it does not affect the the stable isotope values of the samples. Freezedrying is a common method used for the removal of water from biologic samples; Samples should not be acidified for nitrogen isotope analysis. Moreover, acidification is needed for carbon stable isotope analysis in samples of SOM, POM, plankton and crustaceans. Samples should be washing before acidification, while should not be after acidification.The results of813C and δ15N values of the typical algae in Northern Sea showed that the carbon and nitrogen isotopic signatures of phytoplankton were differ among di-fferent phytoplankton species. There were significant positive correlation between813C values and concentration of NO3-and PO43-. There were significant negative correlation between815N values and concentration of NO3-, while significant negative correlation between815N values and concentration of PO43-.General trend of813Cand δ15N valuesin POMwas increasing from land to sea. Seasonal variation of813C and815N values were not significant (p=0.84and p=0.55, respectively). The isotopic values of SOM and POM had the same trend. There were significant differences813C and815N values in sediment in each station (p<0.01). The813C values of sediment in different seasons had not significant differences (p=0.31), while815N values were significant differences (p<0.05). The δ13C and δ15N values of benthos were different with season. The trophic level in benthic food web was from2.07to3.92. The δ13C and815N values ofzoobenthos in Liaodong Gulf were higher than northern Yellow Sea (except815N in Tubulanus punctatus). Studies on the stable isotope ratios of the main nekton (55species) indicated that813C rangingfrom-20.90‰to-13.96‰, and δ15N from8.69‰to14.25‰. The trophic level was from3.02to4.59. The813C and δ15N values between Liaodong Gulf and northern Yellow Sea were not significant differences except Charybdis japonica and Sebastes schlegeli. The813C and815N of nektonvalues were logarithmic correlation to the body length. Trophic level was closely related to the body weight. The average815N values were significant correlation to the body size (log2). The ratio of predator and food resources in the study area was904.26.