Seasonal cycling of zinc and cobalt in the Southeast Atlantic along the GEOTRACES GA10 section

Wyatt, NJ, Milne, A, Achterberg, EP, Browning, TJ, Bouman, HA, Woodward, EMS and Lohan, MC 2020 Seasonal cycling of zinc and cobalt in the Southeast Atlantic along the GEOTRACES GA10 section. Biogeosciences. https://doi.org/10.5194/bg-2020-42 (Submitted)

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Abstract/Summary

We report the distributions of dissolved zinc (dZn) and cobalt (dCo) in sub-tropical and sub-Antarctic waters of the Southeast Atlantic Ocean during austral spring 2010 and summer 2011/12. A strong seasonal signal was observed in sub-tropical surface waters with early spring mixed-layer dZn and dCo concentrations of 3.16 ± 1.35 nM and 39 ± 9 pM, respectively, compared with summer values depleted well below these levels by biological activity. The elevated spring mixed-layer dZn concentrations resulted from an apparent offshore transport of elevated dZn at depths between 20 – 50 m, derived from lithogenic inputs from the Agulhas Bank. In contrast, open-ocean sub-Antarctic surface waters displayed largely consistent interseasonal mixed-layer dZn and dCo concentrations of 0.11 ± 0.08 nM and 11 ± 5 pM, respectively. The vertical distributions of dZn and dCo in the upper water column were similar to that of phosphate (PO4 3-), with positive linear relationships during each of the seasons and 30 across dynamic biogeochemical regimes, suggesting surface biological drawdown and shallow remineralisation of these metals in this region largely influences their distribution. The ecological stoichiometries for dZn and dCo, calculated from the linear regression with PO4 3-, suggest a greater overall use of dZn relative to dCo in the upper water column of the Southeast Atlantic with an inter-seasonal Zn:Co ratio ranging between 9 and 29. Sub-tropical surface water Zn:Co ratios were found to decrease between spring and summer indicating a preferential removal of dZn relative to dCo between seasons. In this paper we investigate how the seasonal influences of external input and phytoplankton succession may relate to the distribution of dZn and dCo, and variation in Zn:Co ecological stoichiometry, across two distinct ecological regimes in the Southeast Atlantic.

Item Type:	Publication - Article
Subjects:	Chemistry Marine Sciences Oceanography
Divisions:	Plymouth Marine Laboratory > Science Areas > Marine Biochemistry and Observations
Depositing User:	Malcolm Woodward
Date made live:	15 Jan 2021 14:00
Last Modified:	15 Jan 2021 14:00
URI:	https://plymsea.ac.uk/id/eprint/9084

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