On the presence of a cadmium-rich subsurface water mass in the western Mediterranean and its influence on the distribution of cadmium in the surface waters

Abstract

Vertical distribution of cadmium (27–133 pM) at 13 stations in the Alboran Sea (western Mediterranean) showed profiles that were different from those typically known from oceanic waters. A subsurface cadmium-rich layer, related to the presence of Winter Intermediate Water (WIW), was a prominent feature. The WIW is formed in the northwestern coastal sector of the western Mediterranean Sea, and the high cadmium concentrations in this water mass are therefore likely to be of coastal origin. The surface concentrations of cadmium at all stations in the Alboran Sea were higher and increased, but not progressively, from west to east, with a substantially higher concentrations around the Almeria–Oran front than on either side. As shown by the cadmium–salinity diagram and the rates of diffusive transfer of cadmium from the subsurface into the surface waters, flux from WIW is an important source of cadmium for surface waters in the Alboran Sea, with a marked increase in the rates near the front.