A microbial methane factory
The serene surface of Thale Noi, a vast freshwater wetland in southern Thailand, hides a turbulent microbial process. Below the water, in the oxygen-deprived peat soil, armies of microorganisms are decomposing immense stores of organic matter. This anaerobic digestion produces large quantities of methane (CH₄), a greenhouse gas with a warming potential many times that of carbon dioxide. The specific area of intense study is the Phru Khuan Khi Sian peat swamp, part of the larger Thale Noi complex. This site became Thailand's first Ramsar Wetland of International Importance in 1998.
The source of this methane production consists of archaea known as methanogens. In tropical peatlands like Thale Noi, the dominant methanogens are often hydrogenotrophic, meaning they produce methane by reacting hydrogen with carbon dioxide. Studies in Thai peat swamps have identified microbes from the class Methanomicrobia as prevalent. These organisms thrive in the waterlogged and anoxic conditions of the peat. The constant high temperatures and abundant organic material from decaying wetland plants create ideal conditions for methanogenesis year-round. While some methane is consumed by other microbes called methanotrophs, a substantial amount escapes into the atmosphere. The water level controls these emissions; when the water table is high, anaerobic conditions expand, and methane production increases.