Spatiotemporal variation of some metal concentrations in oysters from the Mali Ston Bay, south-eastern Adriatic, Croatia - potential safety hazard aspect

The concentrations of cadmium, lead and zinc were determined in the soft tissue of oysters (Ostrea edulis L.) from three locations in the Mali Ston Bay on the south-eastern coast of the Adriatic Sea. The sampling was performed during two periods of breeding cycle, in summer (age ~1 year) and winter (age ~20 months, consumption size). The concentrations of cadmium, lead and zinc measured in the oyster soft tissue showed considerable spatiotemporal variations that could be attributed to seasonal differences in the freshwater inflow which varied between the study locations. Median concentrations measured at different locations and in different time periods ranged from 0.303 to 0.969, 0.13 to 0.32 and 208.9 to 650.0 µg/g wet weight for cadmium, lead and zinc, respectively. Although metal concentrations do not exceed the maximal legally approved limits according to the legislation of the Republic of Croatia and EU, more knowledge of their spatiotemporal distribution - of cadmium in particular - would contribute to the sustainable future development of oyster farming in Croatian waters.