Trace metal fronts in European shelf waters

The Hebrides shelf edge area is characterized by strong horizontal salinity gradients (fronts) which mark the boundary between Scottish coastal and oceanic waters 1,2 . The results presented here, obtained in summer 1981 on a transect between the open North Atlantic and the German Bight (Fig. 1), confirm that the hydrographical front is accompanied by dramatic increases in inorganic nutrients (phosphate, silicate) and dissolved trace elements such as Cd, Cu, Mn, and 226 Ra (Figs 2 and 3). These data (together with measurements from North Sea regions) suggest that the trace metals are mobilized from partly reduced (organic-rich) sediments and vertically mixed into the surface waters 3 . The regional variations evident from the transect are interpreted as being the result of the hydrography prevailing in waters around the British Isles 4 .