Hydrothermal ecosystems

The submarine hydrothermal ecosystems are constituted by complex biological systems whose functioning is little known.
Many of these ecosystems are located at great depth, usually between 1,000 and 4,000 meters, settled along the ridges and in other underwater volcanic areas.
They are fluid emergency zones rich in hydrocarbons, gases and sulfur salts and other mineral substances.
Despite the apparent hostility of the conditions of temperature, pressure and chemical composition of water, these ecosystems have a rich biodiversity.
The species present include large mussels and clams 30 centimeters long, huge tubular worms with long peduncles (exceeding two meters long), corpulent crabs and other invertebrates. The whole ecosystem rests on a very rich bacterial flora that takes advantage of the chemical and thermal energy of the emanations to develop its metabolism and that often lives in a symbiotic relationship with the local multicellular organisms.
The sources of energy in these environments are mainly chemical type based on the oxidation and hydration of hydrocarbons (in particular of methane, generating methane hydrates) and hydrogen sulfide. In some cases the emanations are hot, but there are also places where there are cold springs of oil, hydrocarbon gases and sulfur.
Many of these bacteria belong to the large group of archaebacteria (archaea), including those generically called "hyperthermophilic". Hyperthermophilic can live in very high temperatures of 45o. centigrade or more. Some even develop better with temperatures above 80o.
T. Gold notes that its waxy membranes allow exchanges at elevated temperatures (at colder temperatures they harden and do not work properly).
This author notes that the boiling temperature of water, which at the surface is 100o, rises to 300o at only 876 meters of depth at sea. The critical point where the vapor and water-liquid phase appear undifferentiated is 2,250 meters deep.
In many underwater hydrothermal communities water is a "supercritical" fluid and therefore there are no problems of boiling water that could affect the vital processes, as it happens on the surface.
For that reason, Gold argues, it is possible to imagine that in the pores of the rocks, at great depth, maybe up to 6 or 10 km. there is an abundant population of hyperthermophiles that use available chemical energy, in particular, that which can be extracted from the oxidation of methane and other hydrocarbons.
Methane is a biological fuel that is particularly desirable in depth because its density increases considerably. At 6 kilometers depth, methane is 400 times denser than on the surface. With that density, the chances of the methane molecules passing through the membranes of the "archaea" are much greater.
On the surface the methanotrophs (methane consumers) are rare groups, however, in depth they are probably the very base of the underground system.
This deep biothermic system is what Gold calls "the deep hot biosphere".
In many perforations hyperthermophilic communities have been detected at great depth. The author mentioned above provides two examples: an Alaskan oil well where "active biology" could be recorded at a depth of 4,200 meters and a temperature of 110o centigrade and a well of 5,200 meters in Sweden where the presence of anaerobic microorganisms was found at temperatures from 60 to 70o.
In continental hydrothermal (non-oceanic, often sub-aerial) sources there are other ecosystems that also depend on chemical energy.
The example of Yellowstone hydrothermal springs in the United States is known. The thermophilic communities of these thermal lakes were studied in detail since the 1960s. One of the hyperthermic bacteria identified and described in Yellowstone at that time, the Thermus aquaticus, allowed the first rapid DNA replications that enabled the development of the molecular biological industry of the late twentieth century and early twenty-first century.
The bacteria that inhabit these hot springs use the minerals in a reduced chemical state and oxidizing agents to develop their metabolism. In the thermal lakes other organisms also inhabit that, in most of the cases, are also directly or indirectly dependent on the aforementioned thermo-bacteria.
In a first instance, these submarine and continental hydrothermal environments appear as extreme and anomalous environments.
In Gold's opinion these ecosystems are the mere superficial expression of a huge deep biosphere.
They would not be peculiarities of biology, but on the contrary the modality