https://nwtdiscoveryportal.enr.gov.nt.ca/geoportaldocuments/2021-22%20UofW%28Swanson%29-%20Final%20Report%20CIMP154.pdf

Heidi Swanson, Michael Low, George Low (2022) 2021-22 - Final Report- Understanding fish mercury concentrations in Dehcho lakes(CIMP154), NWT Discovery Portal

In this project, Dehcho AAROM and University of Waterloo have been working together for ~ 10 years to investigate why mercury levels in fish vary among lakes in the Dehcho region, and how mercury levels in fish might change in the future in response to ongoing environmental change. In this three-year phase of the project, we sampled several more lakes (Fish Lake, Greasy Lake, Deep Lake) for fish, water, benthic invertebrates, sediment, and zooplankton. Catchments for all lakes in the study were also characterized. We compiled all available data for this project (dating back to 2013) to model mercury levels in Northern Pike from 11 lakes using piecewise structural equation models. Integrating feedback, ideas, and knowledge from Indigenous Guardians who work together with University researchers on the land each summer, we developed a model that explains >80% of the among-lake variation in mercury levels in Northern Pike. The among-lake variation in fish mercury levels is explained by a complex interaction of catchment characteristics, water chemistry, levels of mercury in lower trophic levels, and fish ecology. Levels of mercury in Northern Pike are lower in lakes that are large relative to their catchments, and which are located in less steep catchments that have proportionally less forest cover. Relatively large lakes located in less forested catchments with shallow slopes have clearer water (less dissolved organic carbon) and lower concentrations of mercury in water and sediment. These lakes also have lower levels of mercury in benthic invertebrates, faster-growing fish, and ultimately lower levels of mercury in Northern Pike.

Annual report for NWT