Movile Cave ― Place That Had Been Isolated From Rest Of The World For Over 5 Million Years

Movile Cave, located deep beneath Romania's Constanta County surface, has been cut off from the outside world and shrouded in darkness for millions of years, crawling with unique life forms.

Movile Cave has been isolated for nearly 5.5 million years; a massive limestone slab fell at that time, so long ago, sealing the cave and its inhabitants off from the rest of the world. Whatever remained inside the dark cavern had to evolve in the absence of sunlight and the air we breathe. 

According to BBC Earth, fewer than 100 people have ever entered the cave. Humans discovered it in 1986 when workers in the Socialist Republic of Romania were looking for new land to build a nuclear power plant.

Once inside the cave, the air contains half as much oxygen as usual and a high concentration of carbon dioxide and hydrogen sulfide. It is also completely dark, having not seen sunlight for at least 5.5 million years.

The central caverns are naturally "guarded" by a series of vertical shafts and narrow limestone tunnels, but it is now closed off by the authorities and only accessible with special permission.

Because the environment is so fragile, only three people are allowed in at any given time. The researchers also change their clothes before entering the cave to avoid bringing in "foreign" microbes.

Despite this harsh environment, scientists have identified 48 species so far. Ranging from spiders, water scorpions, pseudoscorpions, centipedes, leeches, and isopods are among the creatures, with 33 unique to the world.

The majority of the creatures in the cave have lost their ability to see, and their bodies have lost all pigmentation. They're also a spindly bunch, with extra-long limbs and antennae that aid in navigation in the dark.

The cave is unique in several ways: its waters are much warmer than typical limestone caves. It is rich in hydrogen sulfide, which is apparently used to generate energy. 

Serban Sarbu, a biologist from the University of Cincinnati, told the American Association for the Advancement of Science in Baltimore that it is the first known subterranean ecosystem that relies on chemistry rather than sunlight.

Scientists were initially perplexed about how an entire world could thrive under such harsh conditions because no organic matter from the surface makes its way into Movile. The solution can be found in vast "mats" on the surface of the cave's waters and walls. Millions upon millions of tiny bacteria known as autotrophs live in these mats.

The Murrell Lab, part of the University of East Anglia's School of Environmental Sciences, explains that instead of photosynthesis, these autotrophs use chemosynthesis, which obtains chemical energy from the oxidation of sulfur compounds and ammonia in the cave waters. The resulting milky film of microorganisms forms the basis for the rest of Movile's ecosystem.

"These bacteria get their carbon from carbon dioxide just like plants do," says microbiologist Rich Boden, who was then (2010) at the University of Warwick in Coventry, UK. "The carbon dioxide level in the cave is about 100 times higher than normal air. But unlike plants, they obviously can't use photosynthesis as there is no light."

One more intriguing thing is the cave bacteria's autotroph's ability to oxidize methane and carbon dioxide, both of which are significant greenhouse gasses today. It would be fascinating to learn how these bacteria oxidize these two gasses and then develop a technology capable of breaking down the two gasses in our atmosphere to more acceptable levels.