The distribution of dissolved iodine in hebridean waters during mid-winter

The distribution of dissolved total iodine and iodate in the waters off the Scottish coast around the Outer Hebrides in late January 1977 is described. Three types of water are delineated by the iodine results, open ocean proper, outer continental-shelf water, and coastal current water. The results confirm the sluggishness of iodide oxidation in seawater. The region between the ocean proper and the western edge of the coastal current is characterised by interconversion of iodate and iodide with little concomitant loss of total iodine. This behaviour is attributed to biological effects during the previous summer and autumn, and is seen as a general phenomenon extending along the continental margin. Implications are discussed of the finding that some of the Scottish coastal currents contained much lower concentrations of total iodine and iodate concentrations than those observed in the Irish Sea during the previous autumn.