Collaborative Research: Linking Permafrost Soil Inundation to Carbon and Mercury Uptake in Aquatic Food Webs of the Arctic

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The element mercury is a common global contaminant released from human activities that impact both environmental and human health worldwide. One form of mercury, methylmercury, is produced by microorganisms in a process called mercury methylation and can accumulate to toxic levels in aquatic organisms across the food web. Permafrost soils of the Arctic contain large stores of ancient mercury that are also being released to freshwater and coastal marine environments from thawing soils due to a warming Arctic. Women and children in rural communities in the Arctic that rely on subsistence fishing are most vulnerable to the toxic effects of mercury. The central questions surrounding mercury in the Arctic are the relative importance of ancient mercury released from thawing permafrost soils versus newer mercury from the atmosphere, and how rapidly changing conditions in Arctic landscapes will affect the transformations and food web uptake of these different sources of mercury. To address these questions, this study will use multiple approaches to track the releases, transformations, and uptake of both carbon and mercury from permafrost soils to aquatic ecosystems and subsequently to resident fish. The project further aims to develop a practical approach to model the potential for important mercury transformations in lakes and ponds with underlying permafrost soils. Through dialogue with rural communities in Arctic Alaska, we will share what we learn with people who are heavily impacted by mercury pollution. We will also help train the next generation of scientists working on these problems.The study will be carried out using a series of expanding thermokarst lakes and recently formed beaver ponds in U.S. National Park Service lands in northwest Alaska. First, field studies will target the microbial methylation of permafrost mercury and its dependence on permafrost carbon using metagenomics, field experimentation, and measurements of carbon respiration pathways. Next, the uptake of permafrost carbon and mercury in aquatic food webs will be quantified using a combination of radio and stable isotopes (carbon, mercury, nitrogen, and sulfur) and isotope mixing analyses. Isotope mixing models aim to differentiate ancient versus contemporary mercury and carbon in Arctic food webs. The goal is to establish a process-level understanding of the mobilization, microbial transformation, and biotic uptake of carbon and mercury from permafrost soils to aquatic food webs. Lastly, field observations will inform modeling efforts of lakes and ponds to establish linkages between thermal and biogeochemical regimes of water bodies and mercury methylation. This combination of process-level science and predictive model development will provide the necessary information to understand mercury cycling in Arctic systems under present and future conditions. The research findings will be communicated to rural communities in Arctic Alaska through participation in Subsistence Resource Council meetings, to the general public through public presentations and media in collaboration with a science communication specialist at the U.S. National Park Service, and to the scientific community through conference workshops and peer-reviewed journal articles. Undergraduate, graduate, and postdoctoral researchers will cross-train with collaborators across institutions and participate in outreach activities, to develop a diverse and globally competitive STEM workforce to address future environmental challenges beyond this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.