A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. Cold seeps constitute a biome supporting several endemic species.

Entire communities of light-independent organisms - known as extremophiles - develop in and around cold seeps, most relying on a symbiotic relationship with chemoautotrophic bacteria. These prokaryotes, both Archaea and Bacteria, process sulfides and methane through chemosynthesis into chemical energy. More complex organisms, such as vesicomyid clams and siboglinid tube worms use this energy to power their own life processes. In exchange, the microbes are provided with both safety and a reliable source of food. Other microbes form mats that blanket sizable areas.

Cold seeps and hydrothermal vents are similar in that they are the only known ecosystems that do not rely on photosynthesis for food and energy production. Unlike hydrothermal vents which are volatile and ephemeral environments, cold seeps emit at a slow and dependable rate. Likely owing to the cooler temperatures and stability, many cold seep organisms are much longer-lived than those inhabiting hydrothermal vents. Recent research has revealed that the seep tubeworm Lamellibrachia luymesi may be the longest living noncolonial invertebrate known, with a lifespan between 170 and 250 years.

Cold seeps were discovered in 1984 by Dr. Charles Paull in the Gulf of Mexico at a depth of . Since then, seeps have been discovered in other parts of the world's oceans, including the Monterey Canyon just off Monterey Bay, California, the Sea of Japan, off the Pacific coast of Costa Rica, in the Atlantic off of Africa, in waters off the coast of Alaska, and under an ice shelf in Antarctica. The deepest seep community known is found in the Japan trench at a depth of .

Cold seeps develop unique topography over time, where reactions between methane and seawater create carbonate rock formations and reefs. These reactions may also be dependent on bacterial activity. Ikaite, a hydrous calcium carbonate, can be associated with oxidizing methane at cold seeps.

Fossilized records

Cold seep deposits are found throughout the Phanerozoic rock record, especially in the Late Mesozoic and Cenozoic (see for an example, Kaim et al., 2008). These fossil cold seeps are characterized by mound-like topography (where preserved), coarsely-crystalline carbonates, and abundant mollusks and brachiopods.

References

Kaim, A., Jenkins, R., and Warén, A. 2008. Provannid and provannid-like gastropods from the Late Cretaceous cold seeps of Hokkaido (Japan) and the fossil record of the Provannidae (Gastropoda: Abyssochrysoidea). Zoological Journal of the Linnean Society, Volume 154, Number 3, p. 421-436.

External links

• Paul Yancy's vents and seeps page
• Monterey Bay Aquarium Research Institute's seeps page
• ScienceDaily News: Tubeworms in deep sea discovered to have record long life spans