The process of carbon fixation carried out by certain microbes, based on the energy in certain reduced compounds; such as, methane or hydrogen sulfide, as opposed to the use of light energy, as in photosynthesis.

The discovery of chemosynthesis in the deep ocean was possibly the most striking scientific discovery in the field of oceanography during the twentieth century, so much so that scientists now think in terms of "before 1977" and "after 1977."

The ecosystems of the hydrothermal vents depend less on the sun's energy than any of the other systems on the earth.