Trace Metals Cd, Co, Cu, Ni, Pb and Zn in Waters of the Sub- Antarctic and Polar Frontal Zones south of Tasmania - the 'SAZ-Sense' Study

The SAZ–Sense (Sensitivity of the Sub-Antarctic Zone to Environmental Change) project took place in the Australian sector of the Southern Ocean (21 January – 19 February 2007). Its main goal was to compare SAZ waters to the west and east of Tasmania as a model for the effects of climate change. The eastern region is representative of a likely future for the SAZ generally, with incursions of warmer subtropical waters (from EAC eddies). Iron and other trace metal micronutrients were identified as key factors affecting primary production and phytoplankton community composition in the study region. We determined Cd, Co, Cu, Ni, Pb and Zn in SAZ–Sense samples using ICP–MS with in-line preconcentration of the metals by coupled flow analysis – solid-phase extraction. Samples were collected at nine transect stations and three process (longer term) stations spanning waters from the Subtropical Front through the SAZ and PFZ to just south of the Polar Front (northern branch). Non-contaminating procedures were used rigorously throughout all sampling and analysis steps. The metals Cd, Co, Cu, Ni and Zn manifested ‘bio-intermediate’ (nutrient-like) depth profiles universally, with diminished concentrations in surface waters to varying degrees. Whereas, Pb typically had a ‘scavenged’ profile with marginally higher concentrations near the surface. At the Polar Front, the concentration of the micronutrient metals throughout the water column was significantly greater than in SAZ waters; Pb was a contrast, with Polar Frontal waters having less of this toxicant metal than the SAZ. Most metals were at marginally higher concentrations in the SAZ to the east of Tasmania, but Zn and Pb were the opposite with more in SAZ waters to the west of Tasmania.