Selenite toxicity and mercury-selenium interactions in Juvenile Fish

Acute lethal toxicities of selenium and the effects of selenium on mercury accumulation were determined in freshwater fish species. Selenite concentrations required to produce 50% mortality were approximately 11 mg Se/L in northern pike (Esox lucius), 29 mg Se/L in white sucker (Catostomus commersoni), and 5 mg Se/L in yellow perch (Perca flavescens) after 75, 96, and 240 hr of exposure, respectively. Two approaches were used to determine effects of water-borne selenium on mercury concentrations in northern pike. In the first, a trend of reduced mercury contamination at a low selenium concentration (1 ug Se/L) with maintenance at control mercury contamination levels at a higher selenium concentration (100μg Se/L) was apparent. In the second, a similar response of decreased CH₃ ²⁰³Hg accumulation in muscle-skin at lower selenium concentrations (1 and 10μg Se/L), but maintenance at control accumulation levels at a higher selenium concentration (100μg Se/L) was observed. Results and knowledge requirements are discussed with emphasis on relevance to increasing deposition rates of these chemical elements to freshwater ecosystems and using selenium to treat mercury-contaminated aquatic systems.