Spatial and temporal distribution of Fe, Ni, Cu and Pb along 140 E in the Southern Ocean during austral summer 2001/02

• Published in: Marine Chemistry
• Main Authors: Lai, X, Norisuye, K, Mikata, M, Minami, T, Bowie, AR, Sohrin, Y
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science BV 2008
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; Antarctic; Austral; Southern Ocean; The Antarctic; Antarc*; Sea ice
• Online Access: http://www.sciencedirect.com; https://doi.org/10.1016/j.marchem.2008.05.001; http://ecite.utas.edu.au/57169

The distribution of dissolved (D) and acid-dissolvable (AD) Fe, Ni, Cu and Pb in the upper watercolumn (0300mdepth)was determined in the Australian sector of the Southern Ocean (140Emeridian) during three cruises conducted between November 2001 and March 2002. For Ni andCu, therewas no significant difference in concentration between dissolved and acid-dissolvablespecies. DNi and DCu showed significant (P = 0.01) positive correlations with silicate, phosphateand nitrate, reflecting their strong nutrient-type behaviour. For Fe and Pb, the acid-dissolvableconcentration mostly exceeded the dissolved concentration, reflecting the importance of labileparticulate species for these elements. DPb decreased between January and February in thePolar Frontal Zone and in Antarctic continental shelf water. ADPb maxima occurred in theAntarctic Zone, resulting in a maximum AD/D ratio of 7. The mean DFe concentration in thesurface mixed layer was 0.3 nM in the sub-Antarctic zone, 0.4 nM in the Polar Frontal Zone,0.5 nM in the Antarctic Zone and increased southward beyond the Antarctic Divergence andtowards the continent. DFe did not show a clear temporal change in its horizontal distribution,which was in contrast to the other nutrients and trace metals. ADFe substantially increased inAntarctic continental shelf water where the AD/D ratio reached 11. The following conclusionscan be drawn from these data. (1) Ni and Cu exist exclusively as dissolved species and theirdistributions are mainly controlled by their biogeochemical cycling, similar to those of themajor nutrients. (2) Pb is dominated by particulate species. The distribution of DPb istemporally and spatially variable due to a sporadic source and strong scavenging. (3) DFe israther a minor fraction of total Fe in Antarctic continental shelf water where shelf sedimentsand Antarctic sea-ice appear to be strong sources for Fe. There is substantial temporal variationin the supply of Fe to the upper water column. DFe in the mixed layer of the open SouthernOcean is maintained at low concentrations throughout summer due to uptake by phytoplanktonand scavenging.