title: Mercury exposure in the freshwater tilapia Oreochromis niloticus.
abstract: Mercury (Hg) can be strongly accumulated and biomagnified along aquatic food chain, but the exposure pathway remains little studied. In this study, we quantified the uptake and elimination of both inorganic mercury [as Hg(II)] and methylmercury (as MeHg) in an important farmed freshwater fish, the tilapia Oreochromis niloticus, using (203)Hg radiotracer technique. The dissolved uptake rates of both mercury species increased linearly with Hg concentration (tested at ng/L levels), and the uptake rate constant of MeHg was 4 times higher than that of Hg(II). Dissolved uptake of mercury was highly dependent on the water pH and dissolved organic carbon concentration. The dietborne assimilation efficiency of MeHg was 3.7-7.2 times higher than that of Hg(II), while the efflux rate constant of MeHg was 7.1 times lower. The biokinetic modeling results showed that MeHg was the greater contributor to the overall mercury bioaccumulation and dietary exposure was the predominant pathway.
authors.affiliation: Department of Biology, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Ming-Hung
authors.initials: MH
authors.lastname: Wong
authors.forename: Wen-Xiong
authors.initials: WX
authors.lastname: Wang
mesh_terms: D000818:Animals; D023681:Cichlids / Q000378:metabolism*; D004032:Diet; D004781:Environmental Exposure / Q000032:analysis*; D020387:Food Chain; D005618:Fresh Water / Q000737:chemistry*; D007700:Kinetics; D008628:Mercury / Q000032:analysis* / Q000378:metabolism; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury