Cold seep

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Tubeworms, soft corals and chemosynthetic mussels at a seep located 3,000 meters down on the Florida Escarpment. Eelpouts, a Galatheid crab and an alvinocarid shrimp feed on mussels damaged during a sampling exercise.

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 Eubacteria, 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 bacteria are provided with both safety and a reliable source of food. Other bacteria form mats that blanket sizable areas.

Beggiatoal bacterial mat at a seep on Blake Ridge, off South Carolina. The red dots are range-finding laser beams.

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 3,200 meters. 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.^[1] The deepest seep community known is found in the Japan trench at a depth of 7326 m.

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.