Chironomid assemblage changes and deformity prevalence in lakes impacted by uranium mining in northern Saskatchewan, Canada
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Uranium mining has the potential to have impacts on surrounding ecosystems, particularly on the aquatic organisms found in lakes near mining activities. The objective of this study was to use paleolimnological techniques to investigate whether changes occurred in chironomid assemblages or the deformities in head capsules increased in two lakes (I-7 and I-9) impacted by increases in potentially toxic elements associated with mining activities at the McClean Uranium mine. Elemental concentrations of U, As, Mo and Se (excluding Se in I-9) have significantly increased both lake sediments since the introduction of the mine in the late 1960s. Concentrations of Mo differ between Lake I-7 (400 µg g-1) and Lake I-9 (9 ~25 µg g-1) with both increasing several fold following the mine opening. In Lake I-7, Corynocera ambigua and Zalutchia zaluticola decreased from pre-mining to active-mining conditions while Psectrocladius (monospectrocladius) and Polypedilum nubifer increased. Corynocera ambigua dominated the species assemblage (60%) in the pre-mining time period and reduced to minute amounts during active-mining. In Lake I-9, Corynocera ambigua increased slightly in the post-mining time period but there were only minute changes in other taxa between pre-mining and active-mining time periods. Deformities in chironomid head capsules remained low in both lakes and did not change following the initiation of mining actives. There was insufficient literature pertaining to the ability for Corynocera ambigua, Polypedilum nubifer and Psectrocladius (monospectrocladius) to withstand toxic environments except for Polybedilum nubifer which has been previously recorded to demonstrate resistance to the effects of other metals. The stronger change in chironomid assemblage Lake I-7 could have been observed due to the difference in Mo concentration, geographical placement from mining facility and surface area of lake. Multiple stressors could be impacting chironomid assemblage change, including changes in climate. Temperature data of the area showed a probable increase in average annual air temperature between pre-mining and active- mining time periods. More research is needed to attribute changes in chironomid assemblage changes to increases in elemental concentrations, including the need for reference sites away from mining activities.