Higher Mass-Independent Isotope Fractionation of Methylmercury in the Pelagic Food Web of Lake Baikal (Russia)

Lake Baikal's pelagic food web exhibits unusually high mass-independent fractionation (MIF) of methylmercury (MeHg), with Δ(199)Hg values ranging from 3.15 to 6.65‰, significantly higher than coastal fish or typical aquatic systems. This MIF persists across trophic levels, indicating it is driven by biogeochemical processes in the deep, oligotrophic water column rather than trophic transfer. The study, which analyzed Hg isotopes and concentrations in seals, fish, amphipods, zooplankton, and phytoplankton, suggests that MeHg bioaccumulation in this pristine ecosystem is influenced by photodemethylation and long residence times of water masses. These findings highlight the unique isotopic signatures of MeHg in remote freshwater systems.

Perrot, V., Pastukhov, M. V., Epov, V. N., Husted, S., Donard, O. F. X., & Amouroux, D. (2012). Higher Mass-Independent Isotope Fractionation of Methylmercury in the Pelagic Food Web of Lake Baikal (Russia). Environmental Science & Technology, 46(11), 5902–5911. https://doi.org/10.1021/es204572g