Endemic organisms, that are unique to vent ecosystems, have various levels of reliability on the products derived from ‘microbial chemoautotrophy’, as opposed to photo-synthetically derived energy products, where the energy-source is light from the sun, rather than that derived from chemical oxidation-reactions (Desbruyères et al. 2006; Gage & Tyler 1991; Van Dover 2000).
Microorganisms responsible for such chemical reactions may be either ‘free-living’ or closely associated symbionts to vent animals (Gage & Tyler 1991; Pradillon & Gaill 2009). This symbiotic relationship means that some organisms do not have a need to possess a digestive system, e.g. Riftia sp.(Gage & Tyler 1991).
Microbial chemosynthesis occurs where energy is obtained from the fixation of carbon, from reduced inorganic-compounds such as H2S, that is abundant in hydrothermal vent flows (Gage & Tyler 1991; Pradillon & Gaill 2009).
The chemosynthetic bacteria, that are at the base of the trophic level or food chain in vent ecosystems, provide a source of energy for other organisms, these animals then become a source of potential energy for other larger organisms, that may come into close proximities to the vent areas, such as ‘predatory fish or scavengers’ (Gage & Tyler 1991; Tait & Dipper 1998; Van Dover et al. 2002).
Biological rates of production in the vast community surrounding hydrothermal vents is akin to the ‘highest recognised in the oceanic environment’ (Gage & Tyler 1991); which suggests that species living in such areas are well adapted to do so.