Iodine,as a bio-intermediate and redox sensitive element in the oceans,has been proposed to be useful to trace primary production,new production and/or regenerated production.Although it is known that the chemical form is one of the most important factors controlling iodine environmental behavior in the ocean,the actual mechanisms responsible for iodate reduction and iodide oxidation have yet to be fully elucidated due largely to the lack of sensitive iodine speciation analytical methods.