Ground warming releases inorganic mercury and increases net methylmercury production in two boreal peatland types
Boreal peatlands are considered sinks for atmospheric mercury (Hg) and are important sources of methylmercury (MeHg) to downstream ecosystems. Climate change-driven increases in average annual temperature in coming decades will be amplified at higher latitudes and will modify many biogeochemical pro...
| Published in: | Frontiers in Environmental Science |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
Frontiers Media SA
2023
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.3389/fenvs.2023.1100443 https://www.frontiersin.org/articles/10.3389/fenvs.2023.1100443/full |
| Summary: | Boreal peatlands are considered sinks for atmospheric mercury (Hg) and are important sources of methylmercury (MeHg) to downstream ecosystems. Climate change-driven increases in average annual temperature in coming decades will be amplified at higher latitudes and will modify many biogeochemical processes in high boreal and subarctic peatlands that are important landscape features in these regions. Changes in water quality are an important issue for Northern ecosystems and fish consumers, and the directionality of changes in mercury levels due to climate warming presents considerable uncertainty. Peatlands are key landscape hotspots for MeHg production, however, the impact of climate warming on Hg cycling in boreal peatlands is not well studied. We use a multi-year field-based warming experiment (2 years passive, 1 year active ground warming) across two boreal peatland types (moss and sedge dominated) to explore the effects of ground warming on inorganic Hg (IHg) release, net MeHg production, and biogeochemical controls on both of these processes including the availability of sulfate (SO 4 2− ) and dissolved organic matter (DOM) quality and concentration. There were higher porewater IHg and MeHg concentrations under active ground warming conditions in both peatlands, likely related to both increased microbial metabolism, and changes in biogeochemical conditions that favor Hg methylation. Both SO 4 2− (electron acceptor) and bioaccessible DOM (electron donor) are nutrients for sulfate-reducing bacteria which are dominant Hg methylators in freshwater environments, and increases in SO 4 2− and/or bioaccessible DOM concentrations under warming played an important role in the observed changes in net MeHg production. Warming increased SO 4 2− concentrations in the sedge-dominated but not in the moss-dominated fen likely because of a larger pool of groundwater derived SO 4 2− in the sedge-dominated site. Warming increased DOM concentration in both peatland sites through enhanced decomposition of peat and increased ... |
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