| Abstrakt: |
The potential for release of large quantities of biogenic methane to the Earth΄s surface biosphere and atmosphere is the primary means by which this gas could exert an effect that would be global in scale. A considerable amount of methane is produced from biological processes that are directly linked to human activities (e.g., rearing of ruminant livestock, cultivation of rice). Also, the release of biogenic methane due to warming of hydrates in continental and arctic shelf sediments could cause sediment slumps, sustain a biologically-induced anoxia in the overlying water column, and if it enters the atmosphere, cause increased radiative heating of the atmosphere. Under normal conditions, the release of this methane to the surface biosphere occurs slowly enough that microbes oxidize the methane keeping seawater concentrations low. The time scale over which large releases of biogenic methane might occur is speculative and no such events have been directly observed. Nevertheless, the geologic record indicates that methane release from marine sediments probably occurred in the distant past and the current trend towards a warmer Earth may influence the disposition of this methane in the future. Thus, in the biosphere it is the rate of change in methane production and the ability of microorganisms to respond and oxidize the methane that determine whether there are detrimental effects on a large scale. Because of current concerns related to rapid changes in global climate we need a deeper understanding of the role of microbes that mediate the production and consumption of biogenic methane on Earth. [ABSTRACT FROM AUTHOR] |
