Cold seeps refer to areas where hydrocarbon gases and oil naturally seep out of sediments. Methane in particular is used by bacteria as a primary source of energy through a process called chemosynthesis. In sediments without oxygen, the consumption of methane is done with a reduction of sulfates that produces hydrogen sulfides. These sulfides, as methane, can be further used as a source of energy for thiotrophic bacteria. Methanotrophic and thiotrophic bacteria are living either freely in sediments or in symbiosis with larger animals, in particular bivalves and tube worms. The local production of organic matter through chemosynthesis gives rise to flourishing animal communities in an otherwise food-poor deep sea.
Some of these ecosystems are featured on these videos.
In 2006, the international research team of the RENEWZ project, including team leaders A. Baco (WHOI) and A. Rowdan (NIWA), and co PIs Lisa Levin (SIO) and Craig Smith (UH), have observed, for the first time, the deep-sea communities living around methane seeps off New Zealand's east coast. The cruise on board R/V Tangaroa was an exploratory and investigation expedition funded by NOAA OE and NIWA.
In the deep Gulf of Guinea, at 3200 m depth, a large cold seep has been discovered in 2000. Dives of the ROV Victor 6000 allowed to describe and map the various habitats of this particular ecosystem.