Abstract. We report the distributions and stoichiometry of dissolved zinc (dZn) and
cobalt (dCo) in sub-tropical and sub-Antarctic waters of the south-eastern
Atlantic Ocean during austral spring 2010 and summer 2011/2012. In
sub-tropical surface waters, mixed-layer dZn and dCo concentrations during
early spring were 1.60 ± 2.58 nM and 30 ± 11 pM, respectively,
compared with summer values of 0.14 ± 0.08 nM and 24 ± 6 pM. The
elevated spring dZn concentrations resulted from an apparent offshore
transport of elevated dZn at depths between 20–55 m, derived from
the Agulhas Bank. In contrast, open-ocean sub-Antarctic surface waters
displayed largely consistent inter-seasonal mixed-layer dZn and dCo
concentrations of 0.10 ± 0.07 nM and 11 ± 5 pM, respectively.
Trace metal stoichiometry, calculated from concentration inventories,
suggests a greater overall removal for dZn relative to dCo in the upper water
column of the south-eastern Atlantic, with inter-seasonally decreasing dZn / dCo
inventory ratios of 19–5 and 13–7 mol mol−1 for
sub-tropical surface water and sub-Antarctic surface water, respectively. 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 dZn / dCo stoichiometry across these two distinct ecological
regimes in the south-eastern Atlantic.
Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section
