Effects of uranium mining and milling on benthic invertebrate communities in the Athabasca Basin of Northern Saskatchewan

Aquatic environments downstream of uranium operations (mining/milling) in Northern Saskatchewan are exposed to a variety of chemical and physical disturbances. There is extensive regulatory documentation of monitoring and effects assessments for modern uranium operations, though little is available in the scientific literature. The reference condition approach was used to predict expected benthic invertebrate community metrics for unexposed and exposed lakes. This approach was used to identify impacted communities that differed significantly from expected natural regional compositions. The number of taxa at the lowest practical level (taxon richness) downstream of approximately half of the uranium operations' effluent release points was lower compared to the number of taxa observed in reference conditions. The taxon richness residuals were strongly correlated with about half of the measured concentrations of sediment contaminants and always negatively, such that richness was lower in lakes with higher concentrations of metals or radionuclide activities in the sediments. This was consistent for both reference and exposure lakes, implying a natural background influence of some metals and radionuclides on taxon richness. This exercise produced models that can be used by practitioners in the north of Saskatchewan in the design and delivery of monitoring programs not only for uranium mines, but for regional cumulative effects studies in support of sustainable resource planning and management.