Science, Vol 233, Issue 4770, 1300-1303
Copyright © 1986 by American Association for the Advancement of Science
Seasonal variations in the stable carbon isotopic signature of biogenic methane in a coastal sediment
CS Martens,
NE Blair,
CD Green,
and
DJ Des Marais
Marine Sciences Program, University of North Carolina, Chapel Hill 27514, USA.
Systematic seasonal variations in the stable carbon isotopic signature of methane gas occur in the anoxic sediments of Cape Lookout Bight, a lagoonal basin on North Carolina's Outer Banks. Values for the carbon isotope ratio (delta 13C) of methane range from -57.3 per mil during summer to -68.5 per mil during winter in gas bubbles with an average methane content of 95%. The variations are hypothesized to result from changes in the pathways of microbial methane production and cycling of key substrates including acetate and hydrogen. The use of stable isotopic signatures to investigate the global methane cycle through mass balance calculations, involving various sediment and soil biogenic sources, appears to require seasonally averaged data from individual sites.
