Bioaccumulation of selenium (Se) in the Cienega de Santa Clara wetland, Sonora, Mexico

The Cienega de Santa Clara, on the east side of the Colorado River delta, i s a brackish wetland supported by agricultural drainage water front the Uni ted States that provides habitat for endangered fish and bird species, Bioa ccumulation of selenium has created toxicity problems for wildlife in simil ar wetlands in the United States. This is the first selenium survey in the Cienega de Santa Clara. Ten sites mere selected to collect water (dissolved ), sediments (total), plants, invertebrates, and fish. Samples mere collect ed from October 1996 to March 1997, Selenium was detected in all samples. C oncentrations in Rater ranged from 5 to 19 mu g/L and increased along a sal inity gradient. Although water levels of selenium exceeded EPA criterion fo r protection of wildlife, Levels in sediments (0.8-1.8 mg/kg), aquatic plan ts (0.03-0.17 mg/kg), and fish (2.5-5.1 mg/kg whole body, dry wt) did not e xceed USFWS recommended levels, It is concluded from this studs that the le vels of selenium in water did not affect the overall health of the fish sam pled. Therefore, it is important to maintain or improve the mater quality e ntering this wetland to continue to have normal levels of Se in the food ch ain components. (C) 2000 Academic Press.