REGULATION BY LIGHT OF METHANE EMISSIONS FROM A WETLAND

WETLANDS provide up to 25% of the annual global flux of methane-an important greenhouse gas-to the atmosphere1-3. Despite many studies4-9, however, the factors that control emission from wetlands are uncertain. Methane production and transport by rooted vegetation10-15 have been emphasized, but methane oxidation has received little attention. Methane oxidation has been observed in a hardwood swamp7 and may consume >90% of the potential flux from rice paddies16-19. Here I report results from a Danish wetland which suggest that methane oxidation is highly variable, consuming <10% to >90% of the potential methane flux. Laboratory experiments suggest that this variability may be due in part to light-mediated changes in oxygen distribution within illuminated sediments. These results indicate that diffusive fluxes of methane from wetlands may be controlled by rates of oxidation, in addition to rates of methane production. Failure to consider the dynamics and controls of methane oxidation in methane-flux studies could result in incorrect estimates of wetland emission rates. © 1990 Nature Publishing Group.