HR: 15:25h
AN: B22B-07    [PDF]
TI: Use of Stable Isotopes and Incubation Studies to Characterize Methane Production Mechanism in Northern Wetlands
AU: * Chanton, J P
EM: jchanton@mailer.fsu.edu
AF: Department of Oceanography, Florida State University, Tallahassee, Fl 32306 United States
AU: Fields, D
EM: dfields@mailer.fsu.edu
AF: Department of Oceanography, Florida State University, Tallahassee, Fl 32306 United States
AU: Hines, M E
EM: Mark_Hines@uml.edu
AF: Department of Biological Sciences, University of Massachusetts, Lowell, Lowell, Ma 01854 United States
AU: Rooney-Varga, J
EM: Juliette_RooneyVarga@uml.edu
AF: Department of Biological Sciences, University of Massachusetts, Lowell, Lowell, Ma 01854 United States
AB: Arctic and boreal ecosystems are important since they occupy greater than 1/5 of the Earth's terrestrial surface, they are sensitive to subtle climate changes, and they have significant effects on the atmosphere. Methanogenesis is dominated by two major pathways, acetotrophic (i.e., acetoclastic) methanogenesis in which acetate is the immediate precursor of CH4 (and CO2), and H2/CO2 methanogenesis in which CH4 is a product of H2 oxidation coupled with CO2 reduction. Recent studies suggest that acetotrophic methanogenesis does not occur widely in the northern wetlands and acetate can accumulate to high levels (Duddleston et al., 2002; Hines et al., 2001a). Methanogenesis at these sites is dominated by the H2/CO2 pathway and the importance of acetate as a precursor of CH4 seems to decrease with decreasing temperature and increasing oligotrophy. We surveyed a transect across Alaska from Deadhorse to Anchorage and used stable isotope distributions of DIC, CH4 and H2O to discern the relative importance of differing methane production mechanisms. These results compared favorably to incubation studies. Vegetation type was found to be a strong indicator of methane production mechanism, with Carex indicating acetotrophic methaneogenesis and sphagnum being an indicator of a lack of acetate methaneogenesis. The effects of production pathway variation on the dD of methane will also be presented.
DE: 4802 Anoxic environments
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
SC: Biogeosciences [B]
MN: 2003 Fall Meeting