CU AND ZN CONCENTRATIONS OF NATURAL OYSTERS IN OSAKA BAY, JAPAN

Cu and Zn concentrations found in oysters in Osaka Bay were 0.09 to 7.8 ‰ and 1.7 to 37 ‰. Particularly high Cu concentration was found in oysters at fishing ports as well as a yacht harbor and leisure boat wharf. High Zn concentration oysters were also found at fishing ports, yacht harbor, wharf and near food factories. Anti-fouling paint, found in large quantity at the small fishing port, contained Cu2O as a biocide for biofouling and Zn concentrations of anti-fouling paint were also high. This anti-fouling paint was suspected to be the main Cu and Zn contaminant for oysters. Among all oyster parts for natural and cultivated oysters, Cu and Zn concentrations were highest in the oyster gills. Cu and Zn concentrations in the mantle and hepatic gland were almost the same value while adductor muscle values were low. As Cu and Zn concentrations in cultivated oysters were very low, less than 0.1 and 1.1 ‰, natural oysters are considered as effective for getting Zn and Cu in Osaka Bay.