Accumulation, Trophic Transfer, and Health Risk Assessment of Mercury under Typical Ecological Mariculture Models
Global aquaculture is expanding rapidly, with China leading in production and being the only country where aquaculture output exceeds wild catch. This growth raises concerns about environmental contamination, particularly mercury (Hg), and the safety of aquaculture products. This study investigated Hg accumulation and trophic transfer in a typical ecological mariculture area in Tangshan, Hebei Province, by measuring species-specific Hg concentrations in sediments and various aquatic organisms. Sediment total mercury (THg) levels were extremely low, averaging 4.0 ± 1.3 ng·g−1 dry weight (n=56), attributed to sandy/silty sediments with low adsorption capacity and minimal external/internal Hg inputs. In aquaculture fish, muscle THg and methylmercury (MeHg) concentrations were 59.7 ± 30.0 and 53.8 ± 29.2 ng·g−1 wet weight (n=7), respectively, comparable to wild fish from the same area. This is due to efficient trophic transfer and biomagnification of Hg, especially MeHg, along the food chain, influenced by food chain structure, primary consumer accumulation, and metabolic rates. At three seafood consumption levels (41.6–255.6 g·d−1), estimated daily intakes (EDI) of MeHg for Chinese adults ranged from 0.01 to 0.40 μg·kg−1·d−1, with target hazard quotients (THQ) from 0.13 to 3.98. Except for Penaeus monodon and Metapenaeus ensis, all other aquaculture products at high consumption levels exceeded the USEPA safety threshold for MeHg EDI and had THQ > 1, indicating potential health risks.