Methane source

As sources of methane (English cold seep ) are primarily points on the sea floor designated in which methane -rich water exits. This can be both slow and explosive. The bacterial degradation of methane often leads to the precipitation of lime at these points . This limestone can form crusts on the ocean floor, grow downward into the sediment, or rise above the sediment surface. Another manifestation of methane sources are submarine mud volcanoes . Often, communities of highly specialized animals live near methane sources, which use methane as a food source via chemosynthesis.

Occurrence

Methane sources occur worldwide on the edges of the continents, mostly on the continental slope below 200 meters water depth. They are particularly common in geological weak areas where methane-containing water can rise. These include tectonic faults , salt domes and landslides. The first methane sources with their highly specialized fauna were discovered in 1984 on the northern continental slope of the Gulf of Mexico off the coasts of Florida and Louisiana.

Wildlife

In contrast to the generally very thinly populated deep sea floor, many methane sources represent oases that are densely populated with living beings. The fauna that lives here is highly specialized and well adapted to the extreme conditions of the methane sources. Over 80% of the species found here are endemic . Tube worms and mussels, which live in symbiosis with chemotrophic bacteria, are particularly common . These bacteria can use chemosynthesis ( chemotrophy ) to convert methane and hydrogen sulfide into organic compounds, which the animals use as a source of food. In addition to the characteristic tube worms and mussels, there are snails, crabs, shrimp, sea anemones, fish and microorganisms such as nematodes. These biotopes are very similar to those of "black smokers" and are partly inhabited by the same species.

Tube worms (Siboglinidae family)

The tube worm Lamellibrachia occurs in hundreds of thousands at methane springs in the Gulf of Mexico. These animals have completely reduced their stomachs and replaced them with the thecosome, an intestinal sac that houses sulfur bacteria. The bacteria are supplied with hydrogen sulfide from the soil via extensive roots, and the animal takes in oxygen through its gills. Lamellibrachia grows about an inch per year and can live up to 250 years.

The clam Calyptogena

The clam Calyptogena and its relatives from the Vesicomyidae family have also almost completely reduced their stomach. Their greatly enlarged gills are home to sulfur bacteria. The uptake of hydrogen sulfide occurs through its extended foot, which it sticks deep into the sediment. Oxygen is taken from the water using a siphon. Calyptogena occurs worldwide in water depths from 100 meters at methane springs, black smokers and whale cadavers, and can reach a length of up to 25 cm.

Blue mussels (Bathymodiolinae)

The mussel Bathymodiolus is able to harbor both sulfur and methane bacteria. In Bathymodiolus too , the bacteria live in the gill. Methane and hydrogen sulfide are absorbed from the sea water by means of a siphon. In addition, Bathymodiolus has not completely reduced its stomach and can also filter food particles out of the water. Bathymodiolus occurs in water depths between 630 and 3500 meters, at methane springs and black smokers, and reaches a length of up to 30 cm.

Fossils

Fossil remains from methane sources can be lifted to the surface of the earth by plate tectonic processes, making them accessible to paleontologists. Since the limestone is harder and therefore more resistant to weathering than the surrounding sediment, they often form distinctive structures. Such fossils have been known for over 100 years, but their true nature was only understood through the discovery of today's methane sources in the deep sea. Today hundreds of such sites are known, which geologically go back to the Paleozoic . The oldest known methane source is 425 million years old and is located in Morocco.

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Van Dover, CL, 2000. The ecology of deep-sea hydrothermal vents. Princeton University Press, Princeton, 424 pp.