Comparison of mercury bioaccumulation between wild and mariculture food chains from a subtropical bay of Southern China

Bioaccumulation and trophic transfer of mercury (Hg) both in the natural marine ecosystem and the mariculture ecosystem were studied at Daya Bay, a subtropical bay in Southern China. Averaged Hg concentrations in sediment, phytoplankton, macrophyte, shrimp, crab, shellfish, planktivorous fish, carnivorous fish, farmed pompano, farmed snapper, compound feed and trash fish were 0.074, 0.054, 0.044, 0.098, 0.116, 0.171, 0.088, 0.121, 0.210, 0.125, 0.038 and 0.106 mu g g(-1) dw, respectively. These Hg levels were at the low-middle ends of the global range. Positive correlation between Hg concentrations in farmed fish and fish weights/sizes was observed, whereas no clear correlation between Hg concentrations and lipid contents was found. Hg concentrations followed macrophyte < phytoplankton < sediment < planktivorous fish < shrimp < crab < carnivorous fish < shellfish, and commercial feed < trash fish < farmed fish. Hg was biomagnified along the marine food chain in the ecosystem of Daya Bay. Hg levels in the farmed fish were higher than those in the wild fish primarily because of the higher Hg level in fish feed and the smaller size of marine wild fish.