Accumulation of Selenium and Lack of Severe Effects on Productivity of American Dippers (Cinclus mexicanus) and Spotted Sandpipers (Actitis macularia)

Abstract

Selenium has been found at elevated concentrations in water, sediments, and aquatic biota in the Elk River (British Columbia, Canada) and some of its tributaries downstream of several coal mines. Selenium water concentrations in those areas exceed Canadian and British Columbia guidelines and are above levels at which adverse effects to fish and waterfowl could occur. We compared selenium concentrations in the eggs of two riverine waterbirds, American dippers and spotted sandpipers, with measures of productivity: the number of eggs laid, egg hatchability, and nestling survival. In American dippers, the mean egg selenium concentration from the exposed areas, 1.10 +/- SE 0.059 microg/g wet weight, was indistinguishable from the reference areas, 0.96 +/- SE 0.059 microg/g wet weight. For spotted sandpipers, the mean egg selenium concentration in the exposed areas, 2.2 +/- 0.5 microg/g wet weight, was significantly higher than in the reference areas, 1.2 +/- 0.14 microg/g wet weight, but less than reported thresholds for waterfowl and other shorebirds. There were no significant differences in egg hatchability between dippers in reference and exposed areas, but reduced hatchability was apparent for sandpipers in exposed locations. Despite the slightly reduced hatchability in sandpipers, overall productivity was higher than regional norms for both species; thus, selenium did not affect the number of young recruited to local populations. We did not observe teratogenic effects in either species, although none was expected at these concentrations. Despite moderately high selenium concentrations in the water, mean egg selenium concentrations were less than predicted from uptake models. We hypothesise that the relatively low uptake of selenium into the eggs of the two waterbirds in this study is likely due to their lotic environment's low biological transformation and uptake rates.