Cold seeps and hydrothermal vents on the ocean floor support independent biomes without solar energy. They release hydrocarbon-rich fluids and geothermal heated water, hosting chemotrophic bacteria and archaea as primary producers. These biomes also have interesting geological features, including black and white smokers and chimney structures. Cold seeps resemble salt lakes and are home to long-lived life forms.
Cold seeps and hydrothermal vents are structures found on the ocean floor that support biomes completely independent of solar energy. Cold seeps slowly release hydrogen sulfide, methane and other hydrocarbon-rich fluids, while hydrothermal vents release geothermal heated water rich in the same dissolved minerals. Because ocean floors are typically 2-3 miles (3.2-4.8 km) from the surface, these biomes are completely dark for millions of years. They’re also highly pressurized due to the weight of the water above – hydrothermal vent and cold seep biomes usually have ambient pressure a couple of hundred times greater than at the surface.
Cold seeps and hydrothermal vents are the only long-term biomes whose primary producers do not depend on photosynthesis. Instead of photosynthetic bacteria or plants forming the backbone of the ecosystem, this function is performed by chemotrophic bacteria and archaea, which have close symbiotic relationships with the heterotrophic organisms that consume them. In turn, larger organisms – giant tube worms, clams and shrimp – can consume them to survive.
In addition to the diverse biota that hydrothermal vents and cold seeps host, they also possess interesting geological features. Hydrothermal vents can include black smokers, geysers that expel turbid water at a temperature of 400 °C (752 °F), or white smokers, around the same temperature but emitting white rather than black clouds. Because the pressure at these depths is so great, the water does not boil and instead remains in the liquid phase. When superheated solutions come into contact with cold water, the minerals precipitate rapidly, creating chimney structures that can grow up to 60 m (197 ft) before collapsing.
Cold seeps resemble lakes on the ocean floor. Cold seeps release their fluids in the form of brine, which, being denser than typical water, settles to the bottom. Along the edges of these salt lakes, we observe many thousands of mussels, which live on chemotrophic bacteria that feed on the sulphides and methane that escapes from the cold flows. Cold seeps, being more stable than hydrothermal vents, are home to some long-lived life forms, including tubeworms which live 170 to 250 years, the longest of any known non-colonial invertebrate.
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