Martens, C. S.. University of North Carolina at Chapel Hill, cmartens@marine.unc.edu
Albert, D. S.. University of North Carolina at Chapel Hill, albert@marine.unc.edu
Alperin, M. J.. University of North Carolina at Chapel Hill, alperin@marine.unc.edu

 
STABLE ISOTOPE TRACING OF METHANE PRODUCTION AND OXIDATION IN THE GASSY SEDIMENTS OF ECKERNFORDE BAY, GERMAN BALTIC SEA
 
Methane concentrations in the pore waters of Eckernförde Bay in the German Baltic, generally reach gas bubble saturation values within the upper meter of the sediment column. Saturation occurs at a relatively constant depth over large areas of the bay, but moves up and down seasonally according to acoustic reflectivity records as a result of the temperature sensitivity of production and consumption (oxidation) rates. Methane concentration versus depth profiles exhibit an extreme range depending upon the relative importance of production, oxidation, and physical transport processes, including upward freshwater advection associated with local aquifers in the glacial till underlying all of Eckernförde Bay. The relative importance of anaerobic oxidation is indirectly revealed through methane concentration distributions plus combined stable C and H isotope measurements and C isotopic values for dissolved inorganic carbon. The stable isotope measurements provide independent indicators of both the mechanism of methane production and the extent of its oxidation as a function of depth. Direct radiotracer measurements indicate that anaerobic methane oxidation rates of over 40 µM/day are focused at the base of the sulfate reduction zone. Diagenetic equations that describe the depth distributions of the C and H isotopes of methane successfully reproduce isotopic shifts observed throughout the methane oxidation zone and are best fit with kinetic isotope fractionation factors of 1.011 and 1.120 respectively.
 
Day: Tuesday, Feb. 2
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: SS32TU1115E