ECOSYSTEM RECOVERY FOLLOWING SELENIUM CONTAMINATION IN A FRESH-WATER RESERVOIR

Belews Lake, North Carolina, was contaminated by selenium in wastewate r released from a coal-fired electric generating facility during 1974- 1985, Selenium bioaccumulated in aquatic food chains and caused severe reproductive failure and teratogenic deformities in fish, Beginning i n 1986, the electric utility company changed its ash disposal practice s and selenium-laden wastewater no longer entered the lake, A survey o f selenium present in the water, sediments, benthic invertebrates, fis h, and aquatic birds was conducted in 1996, Concentrations were compar ed to pre-1986 levels to determine how much change occurred during the decade since selenium inputs stopped, The data were also examined usi ng a hazard assessment protocol to determine if ecosystem-level hazard s to fish and aquatic birds had changed as well, Results reveal that w aterborne selenium fell from a peak of 20 mu g/liter before 1986, to < 1 mu g/liter in 1996; concentrations in biota were 85-95% lower in 199 6, Hazard ratings indicate that high hazard existed prior to 1986 and that moderate hazard is still present, primarily due to selenium in th e sediment-detrital food pathway, Concentrations of selenium in sedime nts have fallen by about 65-75%, but remain sufficiently elevated (1-4 mu g/g) to contaminate benthic food organisms of fish and aquatic bir ds, Field evidence confirmed the validity of the hazard ratings, Devel opmental abnormalities in young fish indicate that selenium-induced te ratogenesis and reproductive impairment are occurring, Moreover, the c oncentrations of selenium in benthic food organisms are sufficient to cause mortality in young bluegill and other centrarchids because of Wi nter Stress Syndrome, At the ecosystem level, recovery has been slow, Toxic effects are still evident 10 years after selenium inputs were st opped, The sediment-associated selenium will likely continue to be a s ignificant hazard to fish and aquatic birds for years. (C) 1997 Academ ic Press.