Hee, C. University of North Carolina at Chapel Hill, chee@marine.unc.edu
Pease, T. Skidaway Institute of Oceanography, tamara@skio.peachnet.edu
Alperin, M. University of North Carolina at Chapel Hill, alperin@marine.unc.edu
Albert, D. University of North Carolina at Chapel Hill, albert@marine.unc.edu

 
AN ISOTOPIC APPROACH TO MONITORING THE PASSAGE OF CARBON THROUGH THE DOC POOL IN ANAEROBIC MARINE SEDIMENT
 
Dissolved organic carbon (DOC) is an important intermediate in the anaerobic decomposition process. Because DOC is an intermediate, production and consumption are best studied using a tracer approach. We conducted a laboratory degradation experiment in which coastal sediment having a bulk organic carbon del 13C value of -18.7 per mil was amended with phytoplankton (del 13C = -31.0 per mil) or seagrass (del 13C = -8.6per mil) and incubated under sulfate reducing or methanogenic conditions for a year. Subsamples taken on a logarithmic time scale were analyzed for concentrations of particulate organic carbon, total DOC, non-acid volatile (nav) DOC, acid-volatile DOC, dissolved inorganic carbon, and CH4. In addition, we determined stable carbon isotope values of POC and nav-DOC. Concentrations of nav-DOC rapidly increased and nav-DOC isotopic values concurrently deviated towards that of the added carbon indicating that the extant microbial community immediately hydrolyzed the fresh substrates. Rates of fermentation exceeded sulfate reduction and methanogenesis until day 24 resulting in a pooling of acid-volatile compounds such as acetate. Total DOC and nav-DOC isotopic values returned to baseline after three months indicating that DOC derived from the added carbon was a transient pool.
 
Day: Tuesday, Feb. 2
Time: 09:00 - 09:15am
Location: Eldorado Hotel
 
Code: SS34TU0900E