Oxidation of iodide to iodate by cultures of marine ammonia-oxidising bacteria

Reaction with iodide (I−) at the sea surface is an important sink for atmospheric ozone, and causes sea-air emission of reactive iodine which in turn drives further ozone destruction. To incorporate this process into chemical transport models, improved understanding factors controlling marine speciation, especially sea-surface concentrations, needed. The oxidation I− to iodate (IO3−) main oceanic I−, but mechanism remains unknown. We demonstrate first time that nitrifying bacteria mediate IO3−. A significant increase IO3− concentrations compared media-only controls was observed cultures ammonia-oxidising Nitrosomonas sp. (Nm51) Nitrosoccocus oceani (Nc10) supplied 9–10 mM indicating Cell-normalised production rates were 15.69 (±4.71) fmol cell−1 d−1 sp., 11.96 (±6.96) Nitrosococcus oceani, molar ratios iodate-to-nitrite 9.2 ± 4.1 1.88 0.91 respectively. Preliminary experiments on nitrite-oxidising showed no evidence oxidation. If link between ammonia here representative, our ocean cycling model predicts future changes nitrification could alter global fields potential implications chemistry air quality.