Chemosynthesis

Chemosynthesis is the production of organic compounds from carbon dioxide using energy released by chemical reactions rather than light. It supports ecosystems where sunlight does not reach.

Carbon fixation: The conversion of inorganic carbon, usually carbon dioxide, into organic compounds. Chemosynthetic organisms use carbon fixation to turn chemical energy into biomass.
Carbon dioxide: A carbon-containing gas that serves as a major inorganic carbon source for organisms. It supplies the carbon that chemosynthetic pathways incorporate into organic matter.
Hydrothermal vent: An opening in the seafloor that releases geothermally heated, chemically altered fluid. Vent fluids provide reduced chemicals that microbes use to power carbon fixation.
Photosynthesis: The conversion of light energy into chemical energy, commonly coupled to carbon dioxide fixation. Photosynthesis uses light as its energy source, unlike chemosynthesis.
Chemolithotrophy: A metabolism that obtains energy by oxidizing inorganic compounds. It is the broader energy-yielding strategy that powers many forms of chemosynthesis.
Hydrogen sulfide: A colorless, toxic gas with the formula H₂S that can serve as an electron donor. Its oxidation supplies energy to many vent and seep chemosynthetic communities.
Cold seep: A seafloor site where methane-rich fluids escape without the intense heat of hydrothermal vents. Seep microbes oxidize methane and sulfide, supporting dense animal communities.
Photoautotroph: An organism that obtains energy from light and uses it to synthesize organic compounds from inorganic carbon. Photoautotrophs build biomass using sunlight rather than chemical energy.
Oxidation-reduction reaction: A chemical reaction in which electrons move between substances. Electron transfer in redox reactions releases the energy chemosynthetic metabolism captures.
Ammonia oxidation: The conversion of ammonia to nitrite or nitrate through microbial metabolism. Ammonia-oxidizing microbes can power carbon fixation without sunlight.

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