Trace Metal Composition of Suspended Particulate Matter Along Meridional and Zonal Clivar Sections in the Indian Ocean

Abstract:

Total trace element concentrations (Al, Fe, Mn, Cu, Ni, Zn, Pb, Ca, Si, P) were analyzed by X-ray fluorescence on suspended particulate matter samples (>0.4μm) collected at 12-depth profiles in the upper 1000 m of the water column in the Indian Ocean at stations with 1-degree spacing along CLIVAR sections I8S and I9N (February-April 2007) from the Antarctic margin to the Bay of Bengal. Particulate Al distributions reflect large sedimentary inputs from the Ganges-Brahmaputra river system into the Bay of Bengal as well as ice melt and shelf inputs near the Antarctic continent with lower concentrations in surface waters from deposition of aerosol dust. Elevated particulate Fe is evident at depth (>300m) downstream of the Kerguelen plateau, suggesting input of particulate Fe from plateau sediments may fuel surface productivity in this region. Cu, Ni, and Pb are elevated in surface waters centered around 40S, suggesting an anthropogenic signature potentially influenced by local atmospheric deposition or advection into the interior of the basin by the South Indian Ocean Current. In the south Indian Ocean, particulate matter composition reflects high biological production as evidenced by elevated particulate P concentrations in surface waters, with a sharp delineation apparent between high particulate Ca concentrations within the ‘great calcite belt’ (30–55S) and high particulate Si and Zn concentrations in the Indian sector of the Southern Ocean associated with diatom productivity. We will also present particulate trace metal data from CLIVAR zonal transect I5 between South Africa and Australia (May-May 2009) that is currently being analyzed.