Green plants use sunlight to make food by the process of photosynthesis. In the darkness of the ocean depths there is no sunlight for photosynthesis. The answer is found in bacteria that can use another source of energy to make food. Water coming out of a vent is rich not only in dissolved minerals but also in chemosynthetic bacteria . These bacteria are capable of utilizing sulfur compounds to produce organic material through the process of chemosynthesis .
Chemosynthetic bacteria are the primary producers and form the base of vent food webs.
All vent animals ultimately depend on the bacteria for food. When a vent forms, new lava on the ocean floor around the vent becomes covered with a thick mat of bacteria. Soon tiny animals such as amphipods and copepods come to feed on the bacteria. Gradually, larger animals, including grazers, scavengers and predators join in colonizing the vent. Scientists studying a field of vents since their formation in 1991 have observed a pattern of colonization.