Production of Methylmercury in Peatlands Following Permafrost Thaw Increases along a Trophic Gradient
Permafrost thaw in peatlands risks increasing the production and mobilization of methylmercury (MeHg), a bioaccumulative neurotoxin that poses a health hazard to humans. We studied 12 peatlands on a trophic gradient in northwestern Canada, including permafrost peat plateaus and thawed bogs and fens, to determine the effects of thaw on MeHg production from measures of soil and porewater MeHg and in situ methylation assays. The production of MeHg was greater in thawed peatlands, especially rich fens, as indicated by higher potential rates of microbial methylation of inorganic mercury (Hg) to MeHg and higher soil %MeHg (MeHg:total Hg). Soil %MeHg was 0.1% in permafrost peat plateaus, 0.7% in bogs, and 2.0% in fens. Microbial analysis indicated three putative methylators (two methanogens and one novel bacteria) as most influential to the community composition, although their abundances were not consistently highest in fens. Fens had a greater range of porewater MeHg concentrations than bogs, potentially due to hydrological flushing, controls on MeHg solubility, or redox disequilibria in fens. MeHg in porewater was strongly associated with dissolved organic matter that had a low aromaticity and a low oxygen-to-carbon ratio. Regionally upscaling our results suggested that the expansion of bogs and fens due to thawing may increase the landscape-scale potential for MeHg production by 65% by 2100, representing a substantial risk to downstream aquatic ecosystems.
Authors
- David Olefeldt (ORCID: https://orcid.org/0000-0002-5976-1475)
- Lauren Thompson (ORCID: https://orcid.org/0000-0002-6455-4980)
- Lorna I. Harris (ORCID: https://orcid.org/0000-0002-2637-4030)
- Olesya V. Kolmakova (ORCID: https://orcid.org/0000-0003-2694-7545)
- Igor Lehnherr (ORCID: https://orcid.org/0000-0002-4618-7128)
- Andrew J. Tanentzap (ORCID: https://orcid.org/0000-0002-2883-1901)
- Lucas P. P. Braga (ORCID: https://orcid.org/0000-0003-2789-7252)
- Renae Shewan
- Vincent L. St. Louis (ORCID: https://orcid.org/0000-0001-5405-1522)
- William L. Quinton (ORCID: https://orcid.org/0000-0001-5707-4519)
- Chun Cheng (ORCID: https://orcid.org/0000-0003-4907-5487)
- Vaughn Mangal (ORCID: https://orcid.org/0000-0002-6717-5409)
- McKenzie A. Kuhn (ORCID: https://orcid.org/0000-0003-3871-1548)
- Alyssa Azaroff (ORCID: https://orcid.org/0009-0001-2763-8579)
- Charlotte Haugk (ORCID: https://orcid.org/0000-0002-4504-5582)
- Klaus‐Holger Knorr (ORCID: https://orcid.org/0000-0003-4175-0214)
- Oliver Sonnentag (ORCID: https://orcid.org/0000-0001-9333-9721)
Institutions
- University of British Columbia (CA)
- University of Alberta (CA)
- Stockholm University (SE)
- University of Toronto (CA)
- Brock University (CA)
- University of Münster (DE)
- University of Cambridge (GB)
- Institute of Landscape Ecology of the Slovak Academy of Sciences (SK)
- Laboratoire de Géographie Physique (FR)
- Ecosystem Sciences (AU)
- Geomatics (Norway) (NO)
- Trent University (CA)
- Université de Montréal (CA)
- Wilfrid Laurier University (CA)
Publication Details
- Journal
- Environmental Science & Technology
- Published
- 2025-09-04
- DOI
- https://doi.org/10.1021/acs.est.5c04510
- Citations
- 3
- Primary Topic
- Mercury impact and mitigation studies
- Type
- article
- Field-Weighted Citation Impact
- 3.60
Funders
- Polar Knowledge Canada
- Weston Family Foundation
- University of Alberta
- Canada Research Chairs
- Alberta Innovates
- Natural Sciences and Engineering Research Council of Canada
- Fonds de recherche du Québec – Nature et technologies
- H2020 European Research Council