Abstract
At 662PgC, marine dissolved organic matter (DOM) represents the largest pool of reduced carbon and associated elements in the ocean. The flux of carbon and associated elements through the DOM pool operates on time scales that are both ecologically and biogeochemically relevant. As a byproduct of biological productivity a portion of autochthonous DOM production turns over rapidly, serving as a substrate that fuels heterotrophic microbial activity and the fast biogeochemical cycling of elements. Although >50% of the carbon fixed by photo and chemoautotrophy is routed through DOM and processed by heterotrophic microbes, there are numerous biotic and abiotic processes that also alter DOM reactivity, decoupling its production from consumption, resulting in its accumulation. The controls on the redistribution of DOM can play an important role in carbon export and it potential sequestration. This chapter reviews the many production and consumption processes that control the fluxes, accumulation, and inventory of DOM in the ocean. We review (1) the biotic mechanisms of DOM production, (2) the biotic and abiotic processes controlling DOM removal, (3) the numerous factors and processes leading to DOM accumulation, we then (4) examine DOM fractions in terms of biological lability and ecological and biogeochemical significance, and (5) describe our current understanding of the global ocean DOC budget.
