Abstract
Arctic tundra soils store a globally significant amount of mercury (Hg), which could be transformed to the neurotoxic methylmercury (MeHg) upon warming and thus poses serious threats to the Arctic ecosystem. However, our knowledge of the biogeochemical drivers of MeHg production is limited in these soils. Using substrate addition (acetate and sulfate) and selective microbial inhibition approaches, we investigated the geochemical drivers and dominant microbial methylators in 60-day microcosm incubations with two tundra soils: a circumneutral fen soil and an acidic bog soil, collected near Nome, Alaska, United States. Results showed that increasing acetate concentration had negligible influences on MeHg production in both soils. However, inhibition of sulfate-reducing bacteria (SRB) completely stalled MeHg production in the fen soil in the first 15 days, whereas addition of sulfate in the low-sulfate bog soil increased MeHg production by 5-fold, suggesting prominent roles of SRB in Hg(II) methylation. Without the addition of sulfate in the bog soil or when sulfate was depleted in the fen soil (after 15 days), both SRB and methanogens contributed to MeHg production. Analysis of microbial community composition confirmed the presence of several phyla known to harbor microorganisms associated with Hg(II) methylation in the soils. The observations suggest that SRB and methanogens were mainly responsible for Hg(II) methylation in these tundra soils, although their relative contributions depended on the availability of sulfate and possibly syntrophic metabolisms between SRB and methanogens.
| Original language | English |
|---|---|
| Article number | 118878 |
| Journal | Environmental Pollution |
| Volume | 299 |
| DOIs | |
| State | Published - Apr 15 2022 |
Funding
We thank Xiangping Yin for technical support in Hg and MeHg analyses. This research was sponsored by the Office of Biological and Environmental Research within the Office of Science of the U.S. Department of Energy (DOE), as part of the Mercury Science Focus Area (SFA) and the Next Generation Ecosystem Experiments (NGEE-Arctic) projects at the Oak Ridge National Laboratory (ORNL). The Hg isotopes used in this research were supplied by DOE Office of Science the Isotope Program in the Office of Nuclear Physics. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ORNL is managed by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with DOE. We thank Xiangping Yin for technical support in Hg and MeHg analyses. This research was sponsored by the Office of Biological and Environmental Research within the Office of Science of the U.S. Department of Energy (DOE), as part of the Mercury Science Focus Area (SFA) and the Next Generation Ecosystem Experiments (NGEE-Arctic) projects at the Oak Ridge National Laboratory (ORNL). The Hg isotopes used in this research were supplied by DOE Office of Science the Isotope Program in the Office of Nuclear Physics. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). ORNL is managed by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with DOE.
| Funders | Funder number |
|---|---|
| DOE Public Access Plan | |
| Mercury Science Focus Area | |
| U.S. Department of Energy | |
| Biological and Environmental Research | |
| Nuclear Physics | |
| Oak Ridge National Laboratory | |
| Stephen F. Austin State University | |
| UT-Battelle | DE-AC05-00OR22725 |
Keywords
- Acetate
- Mercury
- Methylation
- Microbial community
- Sulfate
- Syntrophy