Behaviour of nickel, copper, zinc and cadmium in the upper 300 m of a transect in the Southern Ocean (57°–62°S, 49°W)

Abstract

Abstract The distributions of Ni, Cu, Zn and Cd in relation to phosphate, nitrate and silicate in the upper 300 m of a transect in the Southern Ocean were studied. This transect covers the Scotia Sea, the Confluence and the Weddell Sea. These three watermasses are clearly separated by their temperature and salinity regimes. Also, the nutrients show different concentration gradients, with that of silicate most pronounced, with concentrations decreasing from 60–80 μM in the Weddell Sea to 20–30 μM in the Scotia Sea. Below 100 m, Cd concentrations are high in the Scotia Sea (∼ 0.8 nM) and lower (∼ 0.6 nM) in the Weddell Sea, but there is still a strong covariance with phosphate. The Cd/phosphate ratio is, however, different in each of the three areas. In contrast with Cd the Cu concentrations are lower (∼ 2 nM) in the Scotia Sea and higher (∼ 5 nM) in the Weddell Sea, and show some relation with silicate. Zn shows the same distribution pattern as Cd, and the relation with silicate is specific for each of the three regions on its own. The distribution of Ni is more complex, but the highest concentrations (8 nM) appear to be in the upper surface layer (200 m) of the Scotia Sea. Lower concentrations (4 nM) are found in the Weddell Sea. Some covariation with the nutrients is found for Ni. It is shown that the surface waters in the turbulent area around the Antarctic Peninsula are not only characterized by their salinity, temperature and nutrient properties, but also by different trace metal contents. In each of the three areas, the differences in the actual concentrations are more dependent on the time of sampling (receding ice-edge, primary production) than on the exact sampling position.