Impact of Photochemistry on Carbon Cycling in the Sea

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ABSTRACTOCE-0096413OCE-0096426Photo-remineralization of (DOM) in seawater can occur both directly through the photoproduction of dissolved inorganic carbon (DIC) as CO2 and CO, and secondarily through coupled photochemical and biological pathways acting on other photoproducts. Based on their observed CO and CO2 (DIC) photoproduction rates, the PIs currently estimate that some 0.2-1.5% of DOM (measured as DOC) may be directly remineralized daily, yielding a photochemical half-life for DOC in surface seawater of between 46-347 days. Half-life estimates of DOM are further reduced when photochemically enhanced microbial respiration of photoxidation product substrates is considered. The research to be undertaken in the current proposal is directed at better constraining these estimates and evaluating their biogeochemical significance compared to levels of primary production and microbial activity. Research cruises to a range of coastal and open ocean environments are to be undertaken to better estimate the photochemical carbon flux.