Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section

• Published in: Biogeosciences
• Main Authors: Wyatt, Neil J., Milne, Angela, Achterberg, Eric P., Browning, Thomas J., Bouman, Heather A., Woodward, E. Malcolm S., Lohan, Maeve C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications (EGU) 2021
• Subjects: Antarctic; Austral; Sion; Antarc*
• Online Access: https://oceanrep.geomar.de/id/eprint/49268/; https://oceanrep.geomar.de/id/eprint/49268/13/bg-18-4265-2021.pdf; https://oceanrep.geomar.de/id/eprint/49268/14/bg-18-4265-2021-supplement.pdf; https://doi.org/10.5194/bg-18-4265-2021

We report the distributions and stoichiometry ofdissolved zinc (dZn) and cobalt (dCo) in sub-tropical andsub-Antarctic waters of the south-eastern Atlantic Oceanduring austral spring 2010 and summer 2011/2012. In sub-tropical surface waters, mixed-layer dZn and dCo con-centrations during early spring were 1.60±2.58 nM and30±11 pM, respectively, compared with summer values of0.14±0.08 nM and 24±6 pM. The elevated spring dZn con-centrations resulted from an apparent offshore transport ofelevated dZn at depths between 20–55 m, derived from theAgulhas Bank. In contrast, open-ocean sub-Antarctic surfacewaters displayed largely consistent inter-seasonal mixed-layer dZn and dCo concentrations of 0.10±0.07 nM and11±5 pM, respectively. Trace metal stoichiometry, calcu-lated from concentration inventories, suggests a greater over-all removal for dZn relative to dCo in the upper water columnof the south-eastern Atlantic, with inter-seasonally decreas-ing dZn/dCo inventory ratios of 19–5 and 13–7 mol mol−1for sub-tropical surface water and sub-Antarctic surface wa-ter, respectively. In this paper, we investigate how the sea-sonal influences of external input and phytoplankton succes-sion may relate to the distribution of dZn and dCo and varia-tion in dZn/dCo stoichiometry across these two distinct eco-logical regimes in the south-eastern Atlantic.