Changes in iodine speciation in the Benguela Current upwelling system

Iodine speciation in the oxygen-depleted water mass along the west coast of South Africa was investigated in February 1979. The low oxygen water was related to the presence of a stable density layer with σsub(t) = 26.8, which persists over long time periods. The remineralisation of the area is discussed in terms of the nutrient and iodine profiles and contrasted with deep-sea iodine regeneration. The presence of total iodine concentrations (dissolved and possibly particulate) of up to 6.6 μM is probably accounted for by sediment release. Calculations of possible breakdown rates of phytoplankton suggest a continuous reduction process as the water body travels south, rather than a non-local source of the reduced waters. (author)