Iodine distribution in the Southern Benguela system during an upwelling episode

Iodate and total iodine concentrations have been measured at eight stations along the coast of South Africa, between Cape Town and Cape Columbine, during a period of upwelling. At most, iodine uptake from the water amounted to 0.020 μM, and appeared to be entirely iodate; iodate reduction to iodide was negligible. Meanwhile the profiles of the major plant nutrients and chlorophyll-a showed that the water column was heavily influenced by processes of productivity. Overall then, the system reflected minimal iodate reduction accompanied by extensive uptake of nutrients. This challenges the conventional view, gained from the study of tropical and sub-tropical waters, that iodate reduction in the oceans is coupled closely to nutrient uptake and primary production. The implications of this are explored.