Trace metals Cd, Co, Cu, Ni, and Zn in waters of the subantarctic and Polar Frontal Zones south of Tasmania during the 'SAZ-Sense' project

• Published in: Marine Chemistry
• Main Authors: Butler, ECV, O'Sullivan, JE, Watson, RJ, Bowie, AR, Remenyi, TA, Lannuzel, D
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2013
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; Antarctic; Southern Ocean; Antarc*
• Online Access: https://doi.org/10.1016/j.marchem.2012.10.005; http://ecite.utas.edu.au/83161

Trace metal micronutrients regulate primary production in oceanic surface waters, particularly thosecharacterised as high nutrient, low chlorophyll, such as the Subantarctic Zone (SAZ). Our goal was to evaluatethe distribution and biogeochemistry of Cd, Co, Cu, Ni and Zn in the upper 1000 m of this zone to the south ofAustralia during the SAZ-Sense Project (JanFeb 2007). 13 depth profiles were sampled for dissolved, labilemetal measurements through subtropical and SAZ waters west and east of Tasmania and southward intothe Polar Frontal Zone. We determined Cd from detection limit b4 pM to 900 pM, Co 543 pM, Cu0.221.79 nM, Ni 2.517.31 nM and Zn b0.227.9. Throughout the study area, Cd, Cu and Ni correlated closelywith the macronutrient phosphorus, but their depletion (relative to winter levels) in surface waters differed:Cd (64>96%), Cu (235%), Ni (720%). The profile south of the Polar Front contrasted markedly with all others,having the lowest depletions in surface waters. Another discordancy was some anomalously high Cu concentrationsin surface waters close to Tasmania. Co behaved as a recycled (nutrient) element correlatingwith P and Chla in the top 200 m of the water column, but deeper it was different with a distinct subsurface peak. The characteristicsof this peak suggested lateral supply of dissolved, labile Co from polar surface waters to lower-latitudeocean depths via Antarctic Intermediate Waters. Zn also typified a recycled micronutrient. It was loosely correlatedwith the macronutrient siliconmore strongly to the south and in the Polar Frontal Zone (PFZ). In thevicinity of the Subtropical Front to the east of Tasmania, dissolved Zn was decoupled from other micro- andmacro-nutrients. Its irregular distribution suggested this region's dynamic eddy field and possibly variable supplyand a phytoplankton community dominated by non-diatom species as influential factors. Distributions of Cd,Cu, Ni and Co were much more uniform in the vicinity of the Subtropical Front (only dissolved Fe data fromSAZ-Sense exemplified similar patchiness in distribution as Zn), distinguished solely by being either side of theFront, in subtropical or subantarctic waters. These new data for Cd, Co, Cu, Ni and Zn improve scant coveragefor them in the Australian sector of the Southern Ocean, and provide a basis for linking their distribution toregional primary productivity and variations in phytoplankton community structure.