Collaborative Research: Distribution of extracellular organic compounds in contrasting oceanographic regimes

The microbial loop is an important component of the ocean food web. It is made up of microalgae, bacteria, predators and viruses that are linked together through the exchange of dissolved organic matter. Small organic compounds produced during metabolism (i.e., metabolites) provide the food and energy that supports the microbial loop. However, the identity of most of these compounds remains unknown. This study will use new methods to measure approximately 150 metabolites in samples collected across a range of environmental conditions in the ocean. The samples represent locations that differ in biological productivity and oxygen concentrations. The project will generate a publicly available dataset that will be a resource for future research by the broader oceanographic community and inform efforts to understand ocean metabolism. In addition, the project will support a postdoctoral researcher and a graduate student and offer workshops to broaden use of metabolomics tools. It is currently hypothesized that 25% of global primary production is recycled by the surface ocean’s microbial loop. However, the mechanisms that underpin this flux of labile, biologically-reactive, dissolved organic carbon are not well known. As a result, global ecosystem models currently represent labile carbon flux as a single value of turnover and are unable to predict the dynamic web of chemical-microbial interactions. The research team will examine extracellular metabolites across four oceanic regimes: high productivity/high oxygen, low productivity/high oxygen, high productivity/low oxygen, and low productivity/low oxygen. In each regime, the researchers will quantify small polar biological molecules which represent important products, intermediates, and reactants of core microbial metabolisms. A global chemogeography of exometabolites will be developed using the unique data generated by this study. Understanding the identity and availability of dissolved metabolites across different environmental gradients and microbial consortia represents a critical step forward in developing more accurate predictions of the ocean’s organic carbon cycle. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.