Temporal distribution of trace metals in Antarctic coastal waters

In the framework of the Italian Research Programme in Antarctica, a nearsho re station positioned inside the Gerlache Inlet (Terra Nova Bay, Western Ro ss Sea) was regularly sampled during the Austral Spring 1997/1998, from Nov ember to February. In order to evaluate the physical, chemical and biologic al variations along the water column, measurements of a large number of par ameters were performed at a suitable frequency: temperature, salinity, fluo rescence, suspended particulate matter, concentration of dissolved and part iculate Fe, Cu and Mn, concentration of nutrients and phytoplankton pigment s. Samples of pack ice and marine microlayer were also collected and analys ed. Elaboration of data with regards to temporal and vertical components pr ovided a good description of temporal distribution of trace metals in the c oastal waters of Terra Nova Bay, in relation to the physical and biological processes. Concerning the surface layer, it was found that concentrations are mainly a ffected by the dynamic of the pack ice melting and phytoplankton activity. The first process influences both the input of metals from meltwaters and t he covering of the seawater surface, allowing atmospheric dust input only w hen all ice has been melted or removed. Direct release from ice of particul ate Fe and Cu were clearly shown by surface concentration peaks and by the high concentrations of suspended particulate matter and particulate metals detected in the ice core section interfaced with the seawater. Moreover, a quite complex dynamic dissolved/particulate partitioning was found, which c an account for the temporal uncoupling between the maximum values of partic ulate and dissolved metals. In absence of pack ice, there is evidence of a far-ther input of Fe and Mn due to atmospheric dust brought into the water column through the marine mi crolayer. This picture is complicated by phytoplankton activity, which remo ves micronutrients like Fe and Cu from water, incorporating them into organ ic particulate matter. The dynamic of metal uptake follows that of primary production which, in the studied area, shows a specific trend characterised by two distinct blooms: the first in the second half of December and the s econd in late summer. In intermediate and deep waters, the vertical distribution of Fe and Mn was characterised by a substantial constant profile until January; then, an in crease of particulate metal concentration with depth was observed along wit h a corresponding decrease of the dissolved concentrations. This trend is t ypical of these scavenging-type elements which are removed by particulate m atter during the sinking process, in the absence of well-defined water colu mn stratification. (C) 2001 Elsevier Science BY. All rights reserved.