Seasonal variations of D/H and C-13/C-12 ratios of microbial methane in surface sediments

Appreciable seasonal and spatial variation has been found in the delta D and delta C-13 of gas-phase microbial CH4 produced in the marine sediments of Cape Lookout Bight (CLB), North Carolina. The observations provide indirect evidence that the CLB CH4 delta variation reflects variation in the relative contributions of the main CH4 precursors, acetate and CO2/H2. The delta D-CH4 and delta C-13-CH4 are inversely correlated, indicating that microbial consumption is not responsible for the delta variation. While CLB is not strictly representative of wetlands in general, some of the key microbial processes and environmental characteristics that appear largely responsible for the observed CLB CH4 delta variation are probably similar in typical temperate and high-latitude wetlands.