METHANE OXIDATION IN SEDIMENTS OF A FLOODPLAIN WETLAND IN SOUTH-EASTERN AUSTRALIA

Potential rates of in vitro methane oxidation in sediments from a floo dplain wetland in south-eastern; Australia ranged between 0.05 and 0.4 5 mu mol cm(-3) h(-1). These rates were at least an order of magnitude greater than were potential rates of in vitro methanogenesis, indicat ing that methanotrophic bacteria could intercept most of the methane p roduced in the sediments before it was lost to the atmosphere. This fi nding has implications for environmental management strategies designe d to limit methane emissions from natural wetlands, and for fundamenta l studies of carbon cycling in natural freshwater environments, where methane emissions have been used as an indicator of rates of anaerobic decay of plant detritus. Methane oxidation was an obligately aerobic process, and added sulphate or nitrate could not replace oxygen as a s uitable oxidant. Ammonium had little effect on methane oxidation, but allythiourea nas strongly inhibitory.