Ecological effects of metals in streams on a defense materials processing site in South Carolina, USA

The Savannah River Site (SRS) is a 780 km² U.S. Department of Energy facility near Aiken, South Carolina, established in 1950 to produce nuclear materials. SRS streams are "integrators" that potentially receive water transportable contaminants from all sources within their drainage basins, necessitating a watershed approach to organize contaminant distribution data and characterize the effects of multiple contaminants on aquatic organisms. This study used several lines-of-evidence to assess the ecological effects of metals in SRS streams, including contaminant exposuremodels for apex predators and bioassessments of fish and macroinvertebrate assemblages. Concentrations of metals in sediments, fish, and water were elevated in streams affected by SRS operations, but contaminant exposure models for the river otter Lontra Canadensis and belted kingfisher Ceryle alcyon indicated that toxicological reference values were exceeded only by Hg and Al. Macroinvertebrate assemblage structure was unrelated to sediment metal concentrations. Fish assemblage data were inconclusive. This study indicated that (1) modeling studies and field bioassessments provide a complementary basis for addressing the individual and cumulative effects of contaminants, (2) habitat effects must be controlled when assessing contaminant impacts, (3) sensitivity analyses of contaminant exposure models can help to apportion sampling effort, and (4) most individual metals in SRS streams are unlikely to have significant ecological effects.