Submarine structures made by leaking gases

Submarine structures made by leaking gases are rocks, pavements and pillars up to four metres high and composed of carbonate cement. This cement is produced by microbial oxidation of gases (mostly methane) that bubble up from below the seafloor. Like reefs, they provide shelter for many species such as crabs, conger eels and wolfish but they also support a unique community of chemosynthetic organisms that are able to survive on the methane and hydrogen sulphide gases. Such species include the gutless nematode Astomonema southwardorum, which is thought to have a symbiotic relationship with chemosynthetic bacteria and known only to occur at Scanner Pockmark in the North Sea.