UC Riverside

With the habitat at the Salton Sea, California, expected to decline to conditions unsuitable for wildlife as the Sea shrinks in coming years, efforts are being made to restore this valuable wildlife area. Current plans involve construction of a series of Species Conservation Habitat (SCH) ponds at the south end of the Sea to replace some of the habitat lost and evaluate options for further restoration. There is concern for the accumulation of selenium (Se) in the SCH ponds to levels potentially toxic to the birds they are meant to protect.

In order to evaluate potential Se risk in the SCH ponds, this study employed a novel selenium modeling approach in which Se concentrations in food web organisms were linked to stable isotope data. Two freshwater lakes in Imperial County, CA, Finney Lake and Ramer Lake, were chosen as surrogates for the proposed SCH ponds. Organisms from the aquatic food webs of the two lakes were collected and analyzed for both Se concentration and carbon and nitrogen stable isotope composition. Se concentration was plotted against delta 15N for each lake to develop an empirical relationship between position in the food web and Se concentration that was then used to predict Se concentrations in piscivore and invertivore birds.

Results provide direct evidence for the bioaccumulation of Se in freshwater habitats at the Salton Sea, but indicate that birds should be at little or no risk from Se toxicity in freshwater systems such as those at Finney and Ramer Lakes. Even though multiple food web components had Se concentrations above established toxicity thresholds, predicted bird concentrations were either below or only slightly above a widely used threshold for reduced hatchability.