Methane production in wetlands

Under aerobic conditions the remineralization of organic carbon by microbial action primarily results in the evolution of carbon dioxide. However, when soils flood for prolonged periods of time, oxygen and other inorganic electron acceptors are consumed. The microorganisms begin 

Methane-forming bacteria comprise a family of microorganisms known as Methanobacteria-cae. Although these bacteria are biochemically related, they are divided into different genera on the basis of dissimilar cellular morphology Methanobacterium (rods), Methanococcus (cocci), and Methanosarcina (clusters of cocci). These anaerobes need other fermentative bacteria to metabolize celluloses, sugars, and proteins in detritus into short-chained fatty acids and simple alcohols that can be used by the methanogens. 

Methane may be produced via several metabolic pathways however, in freshwater environments, the main mode of production comes from the splitting of acetate  

Most of this acetate has its origin in the fermentation of organic matter. Methane can also be produced by simple reduction of carbon dioxide  

The low solubility of methane in water limits its diffusive transport in the flooded soil, and most methane is oxidized to carbon dioxide. The aerenchyma of plants mediates the transport of air (oxygen) to the roots and methane from the anaerobic soil to the atmosphere. The flux of gases in the aerenchyma depends on concentration and total pressure gradients and internal structure, including openings of the aerenchyma (see Chapter 7 for details). 

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Conrad R. Control of microbial methane production in wetland rice fields. Nutr. Cycl. Agroecosys. 2002 64 59-69. 

Gaunt J. L., Neue H. U., Bragais J., Grant I. F., and Giller K. E. (1997) Soil characteristics that regulate soil reduction and methane production in wetland rice soils. Soil Sci. Soc. Am. J. 61, 1526-1531. 

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