The dissolved iodate and iodide distribution in the South Atlantic from the Weddell Sea to Brazil

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Abstract Iodide and iodate concentrations are reported and discussed for the WOCE A23 transect from the Weddell Sea north to about 25°S. Iodide concentrations are very low in the surface waters of the Weddell Sea (20 nM) and increase steadily northwards to about 100 nM in the surface waters of the south Atlantic gyre. In deep waters iodide concentrations are low but detectable at 0.5–2 nM. There is no detectable total iodine depletion in the surface waters south of the polar front although there is a small depletion evident north of the front. The results are discussed in terms of the hydrography, nutrient concentrations and phytoplankton activity along the transect. In particular, a systematic change in the relationship between iodide and nitrate along the transect is discussed.