ABSTRACT

This chapter explores the diversity of the Archaea and their role in marine processes. The discovery that Archaea are a major component of ocean microbiota ranks as one of the most significant surprises to emerge from the application of methods to directly sequence 16S ribosomal RNA isolated from planktonic biomass. Production of methane is the final step in the anaerobic biodegradation of organic material. Methanogens show high physiological diversity in morphology, cell-wall constituents, and physiology, and are grouped into a number of orders and genera using these criteria. About 500–600 Mt of methane enters the atmosphere each year. Most comes from the “burps” of ruminant animals, natural wetlands, peat bogs, paddy fields, coal mining, and extraction of oil and gas. Emissions from ocean Archaea are only 1–2% of the total, because most methane is consumed by methanotrophs or trapped under pressure in sediments over millennia as solid methane hydrate.