The seasonal variation in heavy metal accumulation in the food web in the coastal waters of Jiangsu based on carbon and nitrogen isotope technology

Abstract

Research on food web structures in marine ecosystems is an important field in ecology where the interaction of structure and function contributes to understanding biodiversity. The coastal waters of Jiangsu are one of the important fishing bases in China. In recent years, with the development of industry in the coastal waters of Jiangsu, heavy metal (HM) pollution in this region has become more serious. In this study, all samples (including macroalgae, bivalves, cephalopods, gastropods, crustaceans and fish) were collected in the coastal waters of Jiangsu in spring, summer and autumn. Based on the construction of the food web structure using carbon and nitrogen isotope technology, the main methods of material circulation and energy flow were quantified, and the accumulation regularity and seasonal variation characteristics of HMs in the food web were analysed. The results showed that (1) among all the trophic groups, bivalves had the highest enrichment level of HMs, while fish had the lowest. However, fish have a strong ability to enrich Hg, and the main source of Hg enrichment in the human body is edible fish, so more attention should be given to Hg concentrations in fish. (2) In spring, the mean HM concentrations of marine organisms in the coastal waters of Jiangsu were Zn > Cu > As > Cd > Cr > Pb > Ni > Hg, and they were Zn > Cu > As > Pb > Cd > Ni > Cr > Hg in summer and Zn > Cu > As > Pb > Cd > Cr > Ni > Hg in autumn. In total, the concentrations of Zn, Cu and As were the highest, while the mean concentration of Hg in organisms was the lowest. (3) No significant biomagnification of HMs was found in the three seasons. We speculated that overfishing leads to miniaturization and a younger age of organisms, which makes the concentration of highly enriched HMs in organisms with high trophic levels (TLs) lower.