Chemical Analysis of Sediment and Animal Tissues to Assess Environmental…

Fisheries and Oceans Canada (DFO) requires services for to perform Chemical analysis of sediment and and animial tissues to assess environmental impacts of fish farming. In June 2022, Biigtigong Nishnaabeg, a First Nation located just east of Marathon, Ontario licensed an aquaculture facility in the Peninsula Harbour area of Lake Superior, an area of the lake designated as an Area of Concern for mercury and PCB contamination. DFO Science surveyed sediment at the farm and at reference sites as part of a science program looking at cumulative effects. Operation of the farm for 1 growing season resulted in a visible accumulation of organic waste on the sediment and altered sediment and porewater chemistry. An unanticipated finding was that those impacts to the sediment in turn affected mercury mobility and methylation. Detection of elevated mercury methylation in the area with waste accumulation resulted in a decision by Biigtigong Nishnaabeg to suspend the farm license as well as cancellation of the DFO science project. DFO Science at the request of and in collaboration with Biigtigong Nishnaabeg, is now assessing the severity of contamination and measuring/predicting recovery trajectory by comparing how conditions change over time since farm closure.

In 2025, DFO Science, in collaboration with Biigtigong Nishnaabeg Sustainability Department staff, collected sediment samples and invertebrates tissue samples from locations under and around the fish farm as well as from reference locations. Samples are to be analyzed for total mercury, methylmercury, organic content by loss on ignition, elemental analysis of metals via ICP-MS, and elemental carbon and nitrogen analysis.

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