Arsenic and mercury in lake whitefish and burbot near the abandoned Giant Mine on Great Slave Lake

Contaminant levels in fish are of public concern in northern Canada where they are an important food source. In this study, we investigated the concentration of total arsenic, four arsenic species (arsenite (AsIII), arsenate (AsV), dimethylarsinate (DMA), and monomethylarsonate (MMA)), and total mercury (Hg) in the muscle and liver of lake whitefish (Coregonus clupeaformis) and burbot (Lota lota) collected at two sites near the abandoned Giant Mine site (Baker Pond and Yellowknife Bay) and two reference sites more than 25 km away (Chitty Lake and southern Great Slave Lake). Total arsenic concentrations were typically higher in fish tissues collected near the mine site, and higher in burbot than lake whitefish. We found lower concentrations of arsenic in the muscle tissue of adult lake whitefish than juveniles. All four arsenic species were only detected in the liver tissues of adult lake whitefish collected from Baker Pond on the mine site, and juvenile lake whitefish from the adjacent Yellowknife Bay. Mercury levels were highest in fish from Chitty Lake, and higher for burbot than lake whitefish, similar with other research reporting elevated mercury in small northern lakes relative to larger waterbodies. However, mercury levels in fish were not elevated beyond consumption guidelines. Elevated arsenic concentrations in the fish tissues collected near the mine site suggest that the area continues to be a source of arsenic to the aquatic food web; therefore, continued monitoring is warranted, particularly with a large portion of the local population harvesting wild food sources.