The distribution of cadmium in the sea

Abstract

Cadmium occurs in the sea at ultra trace levels. The concentration varies in various regions of the oceans according to the different oceanographic conditions. Among the heavy metal trace-elements with general or potential ecotoxic significance (Pb, Hg, Cu, Ni, Cr, As, Zn), Cd occurs in surface waters of the open oceans in the relatively lowest concentrations, mostly between 0.1 and 20 ng/kg. The lower section of this range corresponds to large areas in the subtropical and central gyres, whereas the upper section of the range is observed in areas of upwelling, at oceanic divergencies and at the subpolar fronts. Somewhat higher values can occur in shelf regions, due to release of Cd from the bottom sediment depot. In areas of pronounced upwelling the values in surface waters may even be raised to 50–70 ng/kg. Comparable or even higher levels are also observed as a consequence of anthropogenic input in polluted coastal waters (viz. e.g. North Sea and particularly its Southern Bight and German Bight).