Monomethylmercury Isotopes Reveal a Hidden Biomagnification Pathway in Marine Ecosystems and Their Environmental Implications
Year: 2026
Type: article
Abstract: Monomethylmercury (MMHg) is a potent neurotoxin to which humans are exposed via fish consumption. However, the relative importance of planktonic and benthic biomagnification pathways to fish MMHg concentrations in marine food webs is challenging to quantify. Here, we apply compound-specific isotope analysis (CSIA) of Hg to identify fish MMHg biomagnification pathways across nearshore bay (NB), marine continental shelf (MCS), and pelagic ocean (PO) regions. We observe significant differences in Δ 199 Hg between MMHg and total mercury (THg), highlighting the limitations of using THg isotopes to resolve MMHg dynamics in the environment. In NB fish, Δ 199 Hg of MMHg closely matches that of benthic invertebrates, while in MCS and PO fish, it aligns with phytoplankton. According to the MMHg isotope binary mixing model, about 85% of MMHg in NB fish derives from the benthic biomagnification pathway, whereas over 90% of MMHg in MCS and PO fish originates from seawater-phytoplankton trophic transfer. These findings reveal that the benthic biomagnification pathway in near-shore regions has been underestimated in previous models, leading to potential uncertainties in evaluating marine Hg cycling and human exposure risks. This study highlights the importance of the benthic biomagnification pathway in coastal environments and demonstrates the potential of the CSIA of Hg for investigating MMHg biomagnification pathways in marine food webs, which provides new insights for global Hg pollution management under the Minamata Convention.
Institutions: Chinese Academy of Sciences, Institute of Geochemistry, State Key Laboratory of Environmental Geochemistry, University of Chinese Academy of Sciences, Pohang University of Science and Technology, Chinese University of Hong Kong, Centre National de la Recherche Scientifique, Observatoire Midi-Pyrénées, Géosciences Environnement Toulouse, Institut de Recherche pour le Développement, Université de Toulouse, China University of Geosciences, China University of Geosciences (Beijing), Tulane University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Shanghai Ocean University, Environment and Climate Change Canada, South China Sea Institute Of Oceanology
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
SDG: Life below water
Open Access status: green
OpenAlex ID: W7128364752