The classic food chains, which rule in virtually all terrestrial ecosystems, are based on the capacity of green plants to fabricate their organic components form CO2 by making use of the energy carried by the sun’s rays. It is the phenomenon called photosynthesis. Animals simply transform the organic matter produced by plants.
In the ocean deeps, the absence of light makes photosynthesis impossible. As far as the ecosystems observed around the hydrothermal springs are concerned, the organic matter is produced by a biological method which utilises a different energy source. This original process is chemosynthesis.
The organisms capable of carrying out chemosynthesis are bacteria, which are found in the chimneys of hot springs, in their black fumes (inside particles in suspension) and even in the skin of certain invertebrates living in the area. These bacteria break down the molecules of hydrogen sulphide ejected by the hydrothermal springs using oxygen they have absorbed from the sea water. From this reaction, they draw energy which they use to fix carbon and therefore to fabricate organic molecules essential to life.
Before the discovery of chemosynthetic bacteria close to hydrothermal springs, scientists had already observed the process of chemosynthesis, particularly during studies of geysers. But they did not imagine that this biological mechanism could be at the origin of a food chain as important as that discovered in the ocean depths.
As at today, scientists have catalogued more than 500 animal species living in the vicinity of hot springs in the Pacific, Atlantic and Indian oceans. 75% of these are species that are found exclusively in this type of surroundings and nowhere else. 50 or so species of fish frequent these areas.
It should be noted that the temperature of the water gushing from hydrothermal springs is extremely high (between 120 and 400°C), but the great majority of the animals living there swim in water which has already been significantly cooled by the surroundings. In fact, on the walls of the chimneys of the hot springs where life is found, the water temperature is between 2 and 30°C. |