Dissolved Trace Metals in the Ross Sea

Abstract

<p> The dissolved (D) trace metals zinc (Zn), cadmium (Cd), cobalt (Co), copper (Cu), iron</p><p> (Fe), manganese (Mn), nickel (Ni), titanium (Ti), lanthanum (La), yttrium (Y), and lead</p><p> (Pb) were analyzed via ICPMS in samples from the Ross Sea obtained during a cruise</p><p> between 20 December 2013 and 5 January 2014. The concentrations of DZn, DCd,</p><p> DCo, DCu, DFe, DMn, DNi, and DTi were significantly lower in the Antarctic surface</p><p> Water (AASW) compared to the other deeper water masses, indicating biological uptake</p><p> and possibly scavenging. In the AASW, DLa and DY were higher than in Winter Water</p><p> (WW). This can be explained by a spring source from ice melt followed by loss during</p><p> summer and autumn, probably due to passive adsorption. Dissolved Pb was low (16</p><p> pM) and no distinction between water masses was possible. Akin to the macro-nutrients</p><p> nitrate and silicate, the modified Circumpolar Deep Water (mCDW) shows elevated DCd</p><p> compared to the shelf water masses. Sea ice melt and ice sheet melt released DZn, DFe,</p><p> DMn, DNi, DY, DLa, and probably DPb into the Ross Sea. However, only DFe, DMn, DY</p><p> and DLa are transported into the Antarctic Circumpolar Current with the outflowing High</p><p> Salinity Shelf Water (HSSW). The bottom nepheloid layer (BNL) released DFe, as well as</p><p> DMn and DCu, into the HSSW whereas lateral transport from land formed a source of</p><p> DMn and DFe. One station in the Ross Sea Polynya was resampled after two weeks,</p><p> during which time the thickness of the BNL increased, with accompanying increases in</p><p> DFe and DMn near the seafloor. In the surface layer nutrients (including micro-nutrients)</p><p> were depleted further. The uptake slopes/stoichiometric ratios of DZn, DCd and DCo</p><p> versus phosphate indicated that the distribution of these metals is related to uptake as</p><p> well as the composition of the phytoplankton community. Estimated stoichiometric ratios</p><p> of Zn and Cd relative to P were higher at a station dominated by Phaeocystis antarctica</p><p> than at diatom-dominated stations, implying a higher utilization of these metals by</p><p> P. antarctica.</p>

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