Iodine in inshore and off-shore marine waters

Abstract

The temporal variation of iodate and total iodine in the Menai Straits and Irish Sea is discussed together with station data for the Atlantic Ocean. Surprisingly little temporal variation was found in either iodate or total iodine even though seasonal nutrient cycling occurred within these water bodies. The iodate concentrations of the temperate Atlantic Ocean, Irish Sea and Menai Straits surface waters were significantly different. These results, together with the known hydrology of the Menai Straits, make it likely that iodate-reducing substances present in terrestrial run-off will be responsible for relatively low iodate concentrations in shallow-seawaters, such as the Irish Sea. However, it is suggested that the low iodate concentrations of tropical surface waters are more likely to have a biological origin. The possibility that the marine iodine system is open to a thermo-dynamical interpretation, as some workers have suggested, is refuted in the case of temperate surface waters as well as deep ocean waters (>200 m). It is shown that existing analyses indicate that below 200 m at oceanic stations, iodate does not vary significantly with depth.