Bioaccumulation and effects of selenium from surface coal mining in an aquatic songbird

Abstract

Open-pit mining operations are hailed for safe working conditions for miners as well as economically and logistically favourable outcomes for mining companies. However, ecological impacts of these operations may persist for decades. Expansions of open-pit coal mining in British Columbia of Western Canada are planned. Governmental regulation of background contaminants leached from these mines into nearby water systems were established to mitigate environmental impacts associated with these operations. We analyzed water, periphyton, invertebrate, and American dipper (Cinclus mexicanus) blood, egg, and feather samples for selenium and mercury exposure related to mining operations in the Elk Valley. We also quantified effects associated with exposure on clutch size and hatching success. Selenium concentrations in water, periphyton, and invertebrates were significantly higher downstream of mines compared to reference sites within and outside of the Elk River watershed. Selenium concentrations in water from exposed sites exceeded current regulatory levels established to protect wildlife by up to 20 times. Mercury concentrations were below toxic levels for birds in all media and did not factor into determination of selenium exposure or effects. Egg selenium concentrations were on average 0.9 times the regulatory threshold. Our stable isotope analyses showed that diets of nesting females included a negligible proportion of higher order consumers. We did not detect a significant effect of selenium on the rate of hatching success or clutch size of dippers nesting in exposed sites. We conclude that at the time of the investigation, selenium exposure was not impairing hatching of American dippers at the sampled locations.