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Oxidation of iodide to iodate by cultures of marine ammonia-oxidising bacteria
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  • Claire Hughes,
  • Eleanor Barton,
  • Helmke Hepach,
  • Rosie Chance,
  • Matt Pickering,
  • Karen Hogg,
  • Andreas Pommerening-Röser,
  • Martin Robert Wadley,
  • David P. Stevens,
  • Timothy D. Jickells
Claire Hughes
University of York, University of York
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Eleanor Barton
University of York, University of York
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Helmke Hepach
University of York, University of York
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Rosie Chance
University of York, University of York

Corresponding Author:[email protected]

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Matt Pickering
University of York, University of York
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Karen Hogg
University of York, University of York
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Andreas Pommerening-Röser
University of Hamburg, University of Hamburg
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Martin Robert Wadley
University of East Anglia, University of East Anglia
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David P. Stevens
University of East Anglia, University of East Anglia
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Timothy D. Jickells
University of East Anglia, University of East Anglia
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Abstract

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 of the factors controlling marine iodine speciation, and especially sea-surface iodide concentrations, is needed. The oxidation of I- to iodate (IO3-) is the main sink for oceanic I-, but the mechanism for this remains unknown. We demonstrate for the first time that marine nitrifying bacteria mediate I- oxidation to IO3-. A significant increase in IO3- concentrations compared to media-only controls was observed in cultures of the ammonia-oxidising bacteria Nitrosomonas sp. (Nm51) and Nitrosoccocus oceani (Nc10) supplied with 9-10 mM I-, indicating I- oxidation to IO3-. Cell-normalised production rates were 15.69 (±4.71) fmol IO3- cell-1 d-1 for Nitrosomonas sp., and 11.96 (±6.96) fmol IO3- cell-1 d-1 for Nitrosococcus oceani, and molar ratios of iodate-to-nitrite production were 9.2±4.1 and 1.88±0.91 respectively. Preliminary experiments on nitrite-oxidising bacteria showed no evidence of I- to IO3- oxidation. If the link between ammonia and I- oxidation observed here is representative, our ocean iodine cycling model predicts that future changes in marine nitrification could alter global sea surface I- fields with potential implications for atmospheric chemistry and air quality.
Aug 2021Published in Marine Chemistry volume 234 on pages 104000. 10.1016/j.marchem.2021.104000