Mn, Fe and I Redox Chemistry and Their Role in Organic Matter Decomposition in the Arabian Sea

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9310792 Luther In the Arabian Sea, with its water circulation constrained by land masses on three sides, the seasonal pattern of primary production and decay driven by the monsoon winds couples with intense heating of surface water to promote formation of an extensive subsurface zone of low-oxygen water--the oxygen minimum zone (OMZ). Particulate organic matter produced in the oxygenated surface ocean sinks into the OMZ, where it may be utilized by microbes that use sources other than oxygen -- namely, dissolved nitrate, iron, manganese, iodate -- for respiration. As part of the U.S.JGOFS Arabian Sea Process Study, the investigators will investigate the role played by iron, manganese, and iodine oxidation-reduction couples in this process. Such a study will contribute to answering two larger oceanographic questions: How does the OMZ influence carbon cycling? Do anaerobic processes dominate in the OMZ? By sampling the water column in the vicinity of the OMZ at a series of stations and coupling concentration data with hydrological data on vertical and horizontal transport rates into a mathematical reaction-transport model, the investigators will estimate how important these minimally understood oxidation pathways are in the regional picture of organic carbon oxidation. ***