Factors affecting the accumulation and removal of mercury from tissues of the American oyster Crassostrea virginica

Adult oysters, Crassostrea virginica (Gmelin) were held in seawater containing 10 or 100 ppb mercury in the form of mercuric acetate for 45 days. Mercury concentration in tissues was determined by analysis of individually homogenized oyster meats using wet digestion and flameless absorption spectrophotometry. After 45 days, average mercury tissue concentration was 91,600 and 12,100 ppb in the 100 and 10 ppb mercury groups, respectively. A slight decline in mercury residues in the 100 ppb group during the accumulation period was attributed to spawning. Clearance of mercury from tissues was studied in a constant temperature regime (25°C±2C^o) for 25 days and in a declining temperature regime (25° to 5°C) for 80 days by exposing treated adults to estuarine water with no mercury added. The biological half-life of mercuric acetate was 16.8 and 9.3 days in the 25°C temperature regime, and 35.4 and 19.9 days in the declining temperature regime, for the 10 and 100 ppb groups, respectively. Smaller oysters (0 to 7 g) consistently accumulated more mercury per gram wet weight than larger oysters (7 to 20 g) in populations exposed to 10 and 100 ppb mercury.