Xu Xiaoyu, Wang Wen-Xiong
Marine Environmental Laboratory, HKUST Shenzhen Research Institute, Shenzhen 518000, China; Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Savannah River Ecology Lab, The University of Georgia, PO Drawer E, Aiken, SC 29802, United States.
Marine Environmental Laboratory, HKUST Shenzhen Research Institute, Shenzhen 518000, China; Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Environ Pollut. 2017 Jan;220(Pt B):1138-1146. doi: 10.1016/j.envpol.2016.11.021. Epub 2016 Nov 28.
Coasts of South China have experienced an unprecedented growth in its marine-caged fish industry. We analyzed mercury concentrations and stable mercury isotope ratios in fourteen fish species from two cage-cultured farms in Southern China. Total mercury concentrations of all species were lower than the human health screening values, but the human exposures through consumption of several carnivorous fish exceeded the USEPA's reference dose. Isotopic compositions in the sediment (δHg: -1.45‰ to -1.23‰; ΔHg: -0.04‰ to -0.01‰) suggested that mercury in these farms were from coal combustion and industrial inputs. Commercial food pellets and fresh fish viscera provided the major sources of methylmercury to the farmed fish and dominated their mercury isotopic signatures. Non-carnivorous fish presented lower δHg and ΔHg values than the carnivorous fish. Using a mixing model, we demonstrated that the majority of mercury in non-carnivorous species came from pellets and in carnivorous fish came from combined diets of pellets and viscera. Meanwhile, methylmercury concentrations and % methylmercury in the fish were positively correlated with δHg values but not with ΔHg values, mainly because fish eating similar feeds maintained similar ΔHg values. Environmental influences of cage farming such as fish feces and uneaten viscera that continuously provide organic mercury to the environments need to be considered.
中国南方沿海的网箱养鱼业经历了前所未有的增长。我们分析了来自中国南方两个网箱养殖农场的14种鱼类的汞浓度和汞稳定同位素比率。所有物种的总汞浓度均低于人类健康筛查值，但食用几种肉食性鱼类对人类的汞暴露量超过了美国环境保护局的参考剂量。沉积物中的同位素组成（δHg：-1.45‰至-1.23‰；ΔHg：-0.04‰至-0.01‰）表明，这些养殖场的汞来自煤炭燃烧和工业排放。商业饲料颗粒和新鲜鱼内脏是养殖鱼类甲基汞的主要来源，并主导了它们的汞同位素特征。非肉食性鱼类的δHg和ΔHg值低于肉食性鱼类。通过混合模型，我们证明非肉食性鱼类的大部分汞来自饲料颗粒，而肉食性鱼类的汞来自饲料颗粒和内脏的混合饲料。同时，鱼类中的甲基汞浓度和甲基汞百分比与δHg值呈正相关，但与ΔHg值无关，主要是因为食用相似饲料的鱼类保持相似的ΔHg值。需要考虑网箱养殖的环境影响，如鱼粪和未食用的内脏，它们会持续向环境中提供有机汞。
