Murky waters: Impacts of disturbances on the mobilization and downstream delivery of mercury and methylmercury
Principal Investigator: Olefeldt, David (8)
Licence Number: 16807
Organization: University of Alberta
Licensed Year(s): 2022 2021
Issued: Apr 20, 2021
Project Team: Lauren Thompson, Lorna Harris, Christopher Schulze

Objective(s): To monitor wetlands, streams, rivers, and lakes in the Dehcho region, with a focus on understanding current and future trends in aquatic mercury and methylmercury.

Project Description: This licence has been issued for the scientific research application No.4875.

This project proposes to monitor wetlands, streams, rivers, and lakes in the Dehcho region, with a focus on understanding current and future trends in aquatic mercury and methylmercury. The region has vast stores of mercury accumulated in organic wetland soils, and there is a risk that disturbances such as permafrost thaw, wildfire, and beaver activity will increase the downstream mobility of mercury and thus its incorporation into food webs. The research team will particularly assess the role of wetlands as primary sources of methylmercury, and how wetland disturbances may affect downstream loadings. The study design will include monitoring of 5 rivers across the Dehcho region, with sampling done in collaboration with the Aboriginal Aquatic Resources & Ocean Management (AAROM) Program. The research team will further target 3 wetland sites to assess how permafrost thaw, wildfire, and beaver activity affects the biogeochemical processes responsible for mercury availability, methylmercury production, and their downstream mobility. These wetland sites will be located at already established research sites, to benefit from available site data and synergies with other ongoing projects. The proposal will aim for the following objectives:
1) Assess baseline information of variability in mercury, and methylmercury in streams and rivers within the Dehcho region: including a) seasonal variability, b) association with watershed land cover of wetlands and lakes, and c) association of mercury with other aspects of water quality - particularly quantity and quality of dissolved organic matter.
2) Assess the biogeochemistry of mercury cycling in wetlands affected by recent permafrost thaw, wildfire, and in beaver dams. The research team will compare thawed peatlands with different nutrient and groundwater connectivity (from bogs, to poor fens, to rich fens). The research team will measure concentrations of mercury and methylmercury in shallow groundwater at all sites, and link it to aspects of peat quality (plant origin, degree of humification), water chemistry (ions, nutrients, dissolved organic matter), microbial communities, and rate of organic matter decomposition (concentrations, 13C isotopic composition, and net fluxes of carbon dioxide and methane).
3) Synthesize the information from the studies above into a spatial framework to predict variability in mercury levels across stream and river reaches within the Dehcho region, and to assess vulnerability to disturbances. Hence, the proposed research will aim to assess which watersheds that may be vulnerable to increased production and mobilization of mercury and methylmercury into downstream lakes and their food webs.

1) Water, Soil, Microbe, and Gas analysis:
All water quality analysis proposed below will be done at the University of Alberta. All mercury and methylmercury analysis (both total and dissolved concentrations) will be done at the Biogeochemical Analytical Services Laboratory, while basic water chemistry, including ion, nutrient, and carbon concentrations, will be done at the Natural Resources Analytical Lab, and analysis of dissolved organic matter composition (UV-vis, fluorescence) will be done in the Catchment and Wetland Sciences Laboratory. Analysis of soil samples will be done through Muenster University, Germany. That laboratory is dedicated to analysis of peat samples in particular, and will yield data on degree of humification (FTIR analysis), elemental composition (C/N elemental analysis and XRF analysis).

2) Monthly monitoring of stream chemistry - focus on mercury levels.
The research team will continue the water quality monitoring of Smith Creek (just south of Wrigley) and Scotty Creek (along Liard Trail) - monitoring that was initiated as part of CIMP199 "An integrated monitoring program for a forested boreal watershed with discontinuous permafrost: cumulative impacts on water quantity and quality from climate warming and anthropogenic pressures". In 2019 the team added mercury and methylmercury to the water quality variables for which they analyzed the water samples. In 2020, the team were not able to visit the site ourselves, but initiated a collaboration with the AAROM program led by Mike Low - and samples were collected monthly from both sites. In 2020, through the collaboration with the AAROM program, the team also started analyzing monthly samples from Kakisa River, Trout River, and Jean Marie River. These rivers have been chosen by the local communities as being of interest for them, and they have longer data-records of general water chemistry that they can which will be useful to interpret the new mercury data. With the three years of continued monthly sampling of these rivers, the team will be able to yield robust data on both inter- and intra-annual variability in mercury and methylmercury levels.

3) Synoptic sampling of a wide range of streams and rivers within the Dehcho:
The research team further propose to do a large-scale synoptic sampling of streams and rivers in the Dehcho region to further the understanding of the spatial variability of mercury levels. This would involve sampling 30-40 streams/rivers within a short time-period (i.e. under similar hydrological conditions). The team would repeat this synoptic sampling 2 or 3 times to get a better sense of the stream average mercury concentrations. The streams would be sampled along the Mackenzie Highway, from the AB/NWT border to Wrigley, and possibly additional sites along the Liard Highway. The team would assess watershed characteristics for each stream that is sampled, including watershed size, peatland cover, lake cover, slope, abundance of thermokarst, recent fires, and carry out a statistical modeling to determine key factors influencing the spatial variability. The team will in particular focus on including streams that drain into lakes that have been studied by CIMP154 "Understanding fish mercury concentrations in Dehcho Lakes". As such, the team would provide much needed information to better interpret variability in lake and fish mercury levels between these lakes.

Local communities are involved in the water sampling and will receive a data report at the end of the year. Preliminary community engagement began in 2019. The research approach was shared with the Wrigley community through posters aimed at a general audience and at community oral presentation in August 2019. Approval regarding our research project and outreach activities was expressed during meetings with the band manager, and land manager, of the Pehdzeh Ki Band Office in Wrigley. They are supportive of annual community presentations to keep Wrigley residents up to date with the research activities. From 2021-2023, the research group will organize annual community lunch meetings in Fort Simpson, and Wrigley to share ongoing results. Lauren Thompson plans to meet with the GNWT Environment and Natural Resources department in 2021 as she has been commissioned to co-write a water quality report; Lauren will report field research results at an "Eye on the Environment" talk to the department. The GNWT Department of Municipal and Community Affairs has been informed of the project. The influence of permafrost thaw methylmercury cycling will be communicated to the Department, and relationships between water quality variables and treatment indices that are specific to the research region.

David Olefeldt has applied for Cumulative Impacts Monitoring Program (CIMP) funding to support this project; if granted, yearly reports will be submitted to CIMP. CIMP informs decision-makers in health planning and environmental management on results to support regulatory processes. The 2030 NWT Climate Change Strategic Framework identifies contaminants such as mercury and their relationship to climate change in one of its strategic goals: Improve knowledge of the climate change impacts occurring in the NWT. This project's results will contribute specifically to the 2030 NWT Climate Strategic Framework Goal #2: Improve knowledge of the climate change impacts occurring in the NWT by monitoring water quality changes due to contaminants.

The fieldwork for this study will be conducted from April 20, 2021 to December 31, 2021.