Seminar: Dr. Craig Carlson, UCSB Dept. of Ecology Evolution and Marine Biology

UNC Marine Sciences’ Assistant Professor Scott Gifford hosts a seminar presented by Craig Carlson, Ph.D.

Presenter Affiliation: University of California, Santa Barbara – Department of Ecology Evolution & Marine Biology

Title: Dissolved Organic Carbon Dynamics, Export & Removal: Insights Gained from Oceanic Transects and Time-Series Programs

Abstract: At ~662 Pg C, oceanic dissolved organic carbon (DOC) represents one of the largest exchangeable pools of organic matter on earth. Microbial community structure and the associated metabolic activities (autotrophy and heterotrophy) help shape the distribution and dynamics of dissolved organic matter (DOM) within the ocean’s surface and interior.  Microbes alter the chemical character of DOC; thus, influencing the magnitude and rate of its uptake. The bulk pool of DOC is comprised of a myriad of compounds that are dynamic on a spectrum of reactivities and turnover times from the most labile (turnover rates of minutes to days) to the most refractory (turnover rates of millennia).  Thus, depending on the reactivity pool of interest, marine DOC can have biological/ ecological significance while recalcitrant pools have more biogeochemical implication with regard to carbon export, sequestration and distribution within the ocean basins.

Components of DOM that resist or escape microbial remineralization in the surface water can persist long enough to be entrained during ventilation of the ocean interior and result in carbon export to the mesopelagic and bathypelagic realms of the ocean.  Recent work indicates that specific lineages of subsurface bacterioplankton respond to these export events, remineralizing the same DOM that had been largely resisted or escaped microbial degradation at the sea surface.  In this seminar, I will present DOC and biogeochemical data collected from the US Repeat Hydrography program along with microbial and DOM dynamics data from the Bermuda Atlantic Time-series Study site to provide insight about DOM accumulation, export and microbial transformation in the North Atlantic Basin.