Controls of methane oxidation in sediments

Abstract

Bacterial oxidation substantially limits methane (CH₄) emissions to the atmosphere. On a global basis, aerobic oxidation likely equals or exceeds abiological losses due to oxidation by hydroxyl radical. Consequently, understanding the biological sink(s) for CH₄ is as important for analyzing CH₄ dynamics as understanding CH₄ production and reactions in the atmosphere. Data from a variety of aquatic systems indicate that as much as 90% of the CH₄ produced in sediments is oxidized as it traverses the oxic zone at the sediment-water or water-air interface. However, reports of considerably lower values suggest that the process of CH₄ oxidation varies in response to a number of factors, many of which have not yet been thoroughly examined. Controls of CH₄ oxidation include, among others, the distribution of molecular oxygen (O₂), the kinetics of O₂ and CH₄ uptake, competition for substrate between methanotrophs and other bacteria and physiological responses to intermittent anoxia. These controls, in turn, are affected by variables such as illumination, benthic photosynthesis, organic concentrations and hydrologic parameters.