Murky waters: Impacts of disturbances on the mobilization and downstream delivery of mercury and methylmercury
Principal Investigator: Olefeldt, David (8)
Licence Number: 16991
Organization: University of Alberta
Licensed Year(s): 2022 2021
Issued: Mar 15, 2022
Project Team: Christopher Schulze, Renae Shewan, Patrick Smith, Kate Marouelli

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.5148.

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 thus 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. This 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, but initiated a collaboration with the AAROM program and samples were collected monthly from both sites. In 2020, through our 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 can 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.

4) Mercury biogeochemistry of different peatland ecosystems:
With permafrost thaw of peat plateau, the site can transition either into bog or fen settings depending on local hydrology. This study aims to assess the differences in biogeochemistry, with focus on the potential production and downstream mobilization of methylmercury, from a range of different peatland sites that vary with regards to their hydrology and water chemistry. The research team intend to find nutrient poor, intermediate, and rich peatland locations near already established research-sites where team members will continue over the next few years to collect complementary data on peatland hydrology and biogeochemistry outside of this proposal: 1) The Smith Creek site near Wrigley (a site that was the focus of CIMP154, and has an eddy co-variance tower); 2) The Scotty Creek research site (station maintains an eddy co-variance tower at the site); 3) The Lutose research site (a site where there have been recent wildfire disturbances within peatlands, Olefeldt maintains two eddy co-variance towers and have conducted several studies on peatland biogeochemistry at the site).

The Lutose site is located 30 km south of the border between the NWT and Alberta, along the MacKenzie highway. The site is not necessary to complete the objectives of the proposal, but it has several advantages. Assuming COVID protocols remain for the 2021 summer, an Alberta site would allow for more frequent visits throughout the summer. All other research in the NWT will have to be done in longer campaigns that include a 2 week quarantine in Hay River. As such, it is likely that field work with HQP from University of Alberta in the NWT for the 2021 summer will be limited to one longer campaign in the middle of the summer, while the monthly sampling of streams and rivers will be done in collaboration with the AAROM program. The Lutose site in Alberta also has the most accessible recently burned peatlands that are easily accessed without helicopter (burned in May 2019, but also sites that burned in 2007 and 2000). The peatland landscape at Lutose is similar to other peatland sites within the NWT, i.e. the knowledge gained at the site is directly transferable to the Dehcho region. Lastly, the Lutose site is located within the Hay River watershed, which drain into the Dehcho region and into Great Slave Lake. The transboundary agreements between the NWT and Alberta supports common principles for cooperative management of the aquatic ecosystem of the Mackenzie River Basin, including the Hay River basin.

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 the 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, NT, and Wrigley, NT to share ongoing results. In 2021, the group delivered plain language reports and posters to Fort Simpson, Kakisa, and Wrigley, and additionally presented a workshop on permafrost thaw in the muskeg to elementary-school-aged youth in Fort Simpson. A team member additionally met with the GNWT Environment and Natural Resources department in 2021 as they were commissioned to co-write a water quality report. 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 was granted Cumulative Impacts Monitoring Program (CIMP) funding to support this project (CIMP 223), so 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 1, 2022 to October 31, 2022