CHANGES IN CONCENTRATIONS OF SELENIUM AND MERCURY IN LARGEMOUTH BASS FOLLOWING ELIMINATION OF FLY-ASH DISCHARGE TO A QUARRY

Elimination of slurried fly ash discharges to a water-filled quarry wa s followed by a steady increase in concentrations of mercury in the ax ial muscle of resident largemouth bass (Micropterus salmoides). Averag e mercury concentrations in bass (adjusted for covariance with fish we ight) increased from 0.02 mug/g to 0.17 mug/g in three years. Aqueous selenium concentrations in the quarry decreased from 25 mug/L to < 2 m ug/L after elimination of fly ash discharges, but selenium concentrati ons in bass remained about three times background levels. Previous stu dies have shown selenium addition to be a viable means of ameliorating mercury contamination in fish in low alkalinity, low pH waters of nor thern Europe and Canada. These results suggest that selenium may also be effective at blocking the accumulation of methylmercury in harder, more alkaline waters.