Chemosynthesis is the process of making food from inorganic compounds, such as hydrocarbons or hydrogen sulfide. In the deep sea, where sunlight does not reach, chemosynthesis makes life on the ocean floor possible. Chemosynthetic deep-sea bacteria form the base of a food web that includes a significant variety of marine life including shrimp, tubeworms, clams, crabs, fish, and octopods, just to name a few.
Chemosynthetic communities have been found in hot springs on land, and in cold seeps, on sunken ships, and even decomposing whale carcasses on the seafloor. While there is only one equation for photosynthesis, there are many possible equations for chemosynthesis, that differ based on what inorganic compounds are available at each location. At hydrothermal vents, the energy from breaking down hydrogen sulfide, a very common compound in vent plumes, drives chemosynthesis in vent bacterial mats. At cold seeps, scientists believe that hydrocarbons such as methane drive the chemosynthetic process, and are still working to figure out the full pathway.