Contaminant Evaluation of Interior Least Tern and Piping Plover Eggs and Chicks on the Missouri River, South Dakota

摘要

The Missouri River in South Dakota is bordered by bluffs containing marine shale. Analyses of shale from these bluffs revealed that they contained maximum concentrations of 13.6 mg/kg dry weight selenium and 9.35 mg/kg dry weight cadmium. Wind and water erode the dry shale bluffs, releasing biologically available selenium to the river. Selenium also is present at relatively high concentrations in Missouri River tributary streams. The waterborne selenium is carried downstream and deposited in slack-water areas near islands and shorelines. Least tern (Sterna antillarum), a federally endangered species, and piping plover (Charadrius melodus), a federally threatened species, nest on Missouri River islands. Addled eggs of both species were collected during the 1988, 1989, and 1990 nesting seasons and were analyzed for selenium and other inorganics. The maximum concentrations (mg/kg dry weight) of selenium detected were 13.0 and 11.1 respectively in piping plover and least tern eggs. Selenium concentrations remained elevated and stable in bird eggs during all three years of the study.