Regeneration of Inorganic Iodine Species in Loch Etive, a Natural Leaky Incubator

Iodine species concentrations and oxygen concentrations were measured in the isolated bottom waters of a Scottish fjord during two separate periods of isolation, each lasting about a year. The rates of biogeochemical change of the species were estimated by allowing for diffusive fluxes from the bottom water. This shows that iodide concentration increased during the two isolations which occurred in the study period, but that a sustained loss of iodate in the first isolation was followed by a gain during the second. Combined, these changes led to a small and gradual increase in total iodine concentration in both isolations. The iodide production is ascribed to regeneration of material with an I:C ratio of the order of 10−5in the sediment. The iodide oxidation rate is small but significant at about 0•03±0•01 μM year−1.