ABSTRACT
Methane (CH4) is the most abundant hydrocarbon in the atmosphere and an important greenhouse gas, which has so far contributed to an estimated 20% of post-industrial global warming. Ocean sediments produce large quantities of CH4 by the methanogenic degradation of organic matter buried under the anoxic sea floor and an annual methanogenesis rate of 85-300 Tg CH4 year has been estimated. However, the ocean is also a major sink of CH4, since most of the CH4 produced is mainly oxidized before it reaches the hydrosphere and the atmosphere, of which more than 90% is consumed by anaerobic oxidation of CH4 (AOM). AOM coupled to the reduction of sulfate is a process mediated by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria. The chapter also presents an overview of the key concepts discussed in this book.
