Stable carbon and nitrogen isotope evidence for the low biomagnification of mercury in marine fish from the South China Sea

The low biomagnification of total mercury (THg) and methylmercury (MeHg) in commercially important marine fish from the south coast of China has been demonstrated through the analysis of stable carbon and nitrogen isotopes. In this study, levels of THg, MeHg and stable carbon and nitrogen isotope ratios were determined. Stable isotope signatures of carbon and nitrogen (C-13/C-12, N-15/N-14) were used to trace the carbon flow and reconstruct trophic interactions. Levels of THg and MeHg in fish muscle samples were <220 ng g(-1). The trophic levels of sampled fish ranged from 2.31 to 5.03. The trophic magnification slopes were ~0.1 for both THg and MeHg, whereas the trophic magnification factor showed that the average biomagnification of THg and MeHg per trophic level was 3.02 and 2.87 ng Hg g(-1) respectively along fish food chains, indicating low biomagnification potential of these mercury species. The low concentrations of MeHg and low biomagnification of mercury in marine fish may result from the trophic levels and habitats of these fish.