Exploring the Microbial Imprint on Deep-ocean Dissolved Organic Matter
Dissolved organic matter (DOM) in the deep ocean is one of the largest reservoirs of reduced carbon on Earth, and yet we know little about its molecular-level composition and spatial and temporal dynamics. Taken as a bulk pool, this material is dilute and highly degraded, residing in the deep ocean for thousands of years. However, recent work has suggested that some deepwater DOM is produced (1) by microbial degradation of particulate organic matter (POM) and (2) by free-living bacterial chemoautotrophy. To reconcile these results, new paradigms are emerging that view interactions among POM, DOM and microbes as integral components of a dynamic and heterogeneous deep-ocean system, with significant impact on the global carbon cycle. To refine these paradigms, novel data are required that provide molecular-level links between microbes and dissolved organic matter on various spatial and temporal scales in the deep ocean. As a first start, I propose a study that would simultaneously examine DOM composition and microbial diversity during an east-west transect of the deep equatorial Atlantic Ocean.