CADMIUM AND ZINC IN MYTILUS-EDULIS-L FROM THE BOTHNIAN SEA AND THE NORTHERN BALTIC PROPER

Contents of Cd and Zn in the blue mussel, Mytilus edulis, collected on the coast of the southern Bothnian Sea and the northern Baltic proper, were determined using flame AAS. The observed concentrations ranged from 4.7 to 10.8 mg kg-1 dw for Cd and from 121 to 215 mg kg-1 dw for Zn. The Zn/Cd ratio was around 20 at a majority of the investigated locations. Cd exhibited an approximate two-fold gradual increase from south to north in the study area. It is likely that this increase was due largely to enhanced bioavailability for Cd at lower salinity. However, it is not possible to eliminate the influence from a generally elevated overall concentration of cadmium in the southern Bothnian Sea caused by natural and anthropogenic input. Compared to mussels from marine waters on the west coast of Sweden, Cd concentrations were 5-10 times higher, similarly indicating an influence of low salinity. Zn did not show these salinity correlated differences. The high Zn content found south of the outlet of the river Dalalven and gradually decreasing southwards was possibly caused by the high riverine input.