Until recently, it seemed that there were no living beings left on Earth that were not known to scientists. We are looking for something new in space, but we must admit that the underground and deep-sea world of our own planet is rather poorly studied. It is there that you can still find incredible miracles.
Movile Cave in Romania became such a miracle for scientists. For five million years, life has existed in it under conditions in which it is simply impossible.
EARTHLIFE ON EARTH
So, in the Romanian cave Movile in 1986, a closed ecosystem was found, in no way connected with terrestrial conditions - neither with sunlight, nor with air, nor with water.
Movile Cave Entrance
Wikipedia gives the following definition to closed ecosystems: “An ecosystem that does not imply any exchange of matter with the external environment. In closed ecosystems, any waste of one biological species must be disposed of at least by another species”.
This natural wonder was discovered quite by accident, during geological research before the construction of a power plant near the city of Mangalia, located in Transylvania on the Black Sea coast. At a depth of 18 m, in an almost completely submerged cave, geologists have discovered a whole world that exists in conditions that are more similar to alien than to Earth.
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There is almost no oxygen in the atmosphere of the cave (7-10%), but it is saturated with hydrogen sulfide, which is contained here in huge quantities, carbon dioxide, methane and ammonia.
This unearthly earthly life, isolated from the outside world, has existed for five million years. The biosystem has surprisingly adapted itself to unusual conditions. Instead of the photosynthesis we are accustomed to, it uses chemosynthesis - a method of nutrition in which the oxidation reactions of inorganic compounds serve as a source of energy for the synthesis of organic substances from CO2.
In a closed stone space with an area of about 1,200 m2, of which only 300 m2 have been investigated to date, scientists have found about 50 species of living creatures (microorganisms, leeches, spiders, scorpions, insects). Slightly more than 30 of them are unknown to science.
It has been established that life in the cave originated in the early Pliocene, at the same time the australopithecines related to man appeared and died out, and then the first people appeared.
For some reason, the cave turned out to be tightly closed, perhaps that is why its inhabitants did not die during the ice ages. They had to adapt to underground life. So they have lived for 5 million years in a dark limestone cave, with a muddy lake dividing the upper part into three isolated cavities. Well at least the water is warm (21 degrees Celsius) thanks to the thermal springs.
CAVE OF THE BLINDERS
All living creatures living in a cave have two common features: they have no color (discoloration), since they live in pitch darkness, and they are completely blind, because without light, they do not need sight. In space, underground inhabitants are guided by touch and smell.
As you know, hearing sharpens in the dark, so the inhabitants of Movil have learned to pick up the slightest vibrations of stone, air and water. Closed systems have their own laws of life, and here symbiosis is very well developed. Each creature helps the other to exist and develop.
Aquatic species live about 10 cm below the surface of the earth: there is slightly more oxygen there than below. And below, only organisms with anaerobic respiration can survive, that is, those in which energy in the body is produced without the participation of oxygen received from the outside.
It must be said that those who receive more oxygen have changed less than the anaerobic ones. Among them, only 25% are endemic. Hence, we can conclude that sea or river water came here for some time after the cave was cut off from the world.
EAT AND SURVIVE
As in all nature, Movil has its own food chain, at the bottom of which there are autotrophic bacteria that synthesize organic substances from inorganic ones, in other words, convert minerals into organic matter. If plants on the surface use sunlight for photosynthesis, then underground inhabitants oxidize hydrogen sulfide for chemosynthesis. As a result, sulfur precipitates, and microorganisms receive energy for the synthesis of organic matter from carbon dioxide and water.
These bacteria feed on other, heterotrophic bacteria and fungi. The latter are then combined into bacterial mats and films that cover the cave walls and water surface. These mats serve as a kind of pasture for other, more developed living creatures: isopods, woodlice, scorpions, which, in turn, are eaten by centipedes and spiders.
Under the water, under the bacterial film, its own food chain is built - there live worms, crustaceans, snails, and above them - leeches and water scorpions. Snails here are extremely resistant to hydrogen sulfide and eat the bacterial film; the water scorpion preys on crustaceans; predatory leeches devour snails, worms and other invertebrates.
And, I must say, this entire ecosystem is working quite productively. On 1 m2, researchers counted 1.5 thousand collembolans, which were hunted by blind spiders, very reminiscent of their counterparts living in the Canary Islands, only sighted. Does this mean that the Pliocene had about the same climate?
DANGER! KEEP OUT
A long stay in the Movile cave is a mortal danger to humans, this is understandable, given the atmosphere in it. And such guests are harmful to the life of the ecosystem. The caver's breathing process alone can cause an imbalance in the gas composition of the atmosphere in the cave.
In order to preserve this miracle of nature, access to the grottoes is allowed only to research scientists in special sterile diving suits with scuba diving. They can only visit the site twice a month in a group of three. The cave is carefully guarded from people and the influence of the external environment. For this, two hermetically sealed hatches are installed at the entrance.
Some researchers argue that today only two closed ecosystems are known in the world: the planetary one and the Movile cave. But no, it's not that bad. Scientists identify at least two more ecosystems that exist in similar conditions.
LIGHT HOUSE CAVE
In the state of Tabasco in southern Mexico, there is the Kislaya Cave, which is a 2 km long labyrinth. It is sometimes called the Cave of the Illuminated House, since here and there daylight still penetrates it through the crevices.
An absolutely terrible picture awaits those who dare to visit this unpleasant place: real sulfuric acid oozes from the walls and ceiling, colorful mucus hangs everywhere on the walls, sometimes forming gelatinous stalactites.
All this is complemented by the disgusting smell of hydrogen sulfide. Sulfuric acid appears here as a result of the oxidation of hydrogen sulfide, which is released from the ground and reacts with water. It was this acid that ate such a huge tunnel in the limestone.
However, life also exists in these uninhabited conditions. Here, as in Movil, bacteria live, oxidizing hydrogen sulfide and receiving energy in the process. The mucus on the walls is a horde of different bacteria, but it also contains mites and worms that eat the bacteria. The walls are inhabited by midge larvae, of which there are so many that you can hear them hum.
But, unlike Movil, you can find more highly developed animals in the Acid Cave. In the stream at the bottom of the cave, schools of fish swim, feeding on bacteria and midge larvae. Although the very fact of the existence of fish in a sulfuric acid solution seems incredible! In the upper sections of the cave, where some air enters, six species of bats live.
Scientists have not yet been able to figure out where the hydrogen sulfide comes from. There are two hypotheses: either it comes from an oil field nearby, or the fault is the El Chichon volcano, also located nearby.
LECHUGILLA CAVE
Another similar ecosystem is located in Lechugilla Cave in the United States. This is one of the deepest caves, its length is 0.5 km in depth. Life in it is also completely isolated from the outside world in its atmosphere contain! a huge amount of hydrogen sulfide.
Only, unlike the other two caves, there are lakes with clear water in Lechugill. But this purity and transparency are deceiving: the water is unsuitable for ordinary inhabitants! aquatic environment. Nevertheless, the reservoirs are quite inhabited by bacteria that feed on … manganese. The walls of the cave are eaten by another type of bacteria.
It's no surprise that NASA is interested in this ecosystem. They hope to get an answer to the question whether there is life on other planets, where there is no oxygen and organic food. And caves like Movil are perhaps ways to persuade scientists to respond positively.
Galina MINNIKOVA, magazine "All the mysteries of the world", number 2, 2016