Movile Cave has remained isolated for close to 5.5 million years, about the same time our ancestors were coming down from the trees in the plains of Africa and beginning the evolutionary journey to becoming humans.
At that time, so long ago, a huge limestone slab fell and sealed the cave and its inhabitants from the rest of the world. Whatever was left inside the dark cavern had to evolve without sunlight or the air we breathe. Yet despite the lack of any light and a poisonous atmosphere, life has thrived, with unique spiders, scorpions, woodlice, and centipedes.
So far, 48 different species in all have been identified, with 33 of the species being entirely unique to the cave. And all of them owe their lives to a strange floating mat or film of bacteria. Most of the creatures have no eyes, are translucent and sport extra long antennae or legs, making it easier for them to get around in the darkness.
The cave was discovered in 1986 when Romanian workers were testing the ground for a power plant site. The first person to enter the cave was Romanian scientist Cristian Lascu. Since that time, less than 100 people have been allowed to make the dangerous descent down into the cave.
Going into the cave is an adventure in itself
To get inside takes some spelunking skills. First, you have to descend by rope some 20 meters (66 feet) down a narrow shaft dug into the ground with only the light on your helmet guiding you. Then you will need to crawl through a number of narrow limestone tunnels coated with a sort-of ochre-colored clay. It is pitch dark and the temperature is a steady 25 degrees Celsius (77 degrees Fahrenheit).
In 2010, microbiologist Rich Boden, who was then at the University of Warwick in Coventry, UK, was lucky enough to be the 29th person allowed to see the cave, according to the BBC. He gave a description of his descent into the cave.
“It’s pretty warm, and very humid so it feels warmer than it is, and of course with a boiler suit and helmet on that doesn’t help,” says Boden, now at the University of Plymouth in the UK. “The pool of warm, sulphuric water stinks of rotting eggs or burnt rubber when you disturb it as hydrogen sulfide is given off.
He is talking about the lake in the central cavern that is reached after crawling through all those tunnels. The lake gives off carbon dioxide as well as hydrogen sulfide. The air inside the cave only contains 10 percent oxygen, compared to our atmosphere that contains 20 percent oxygen. Visitors to the cave can only last about 5 to 6 hours before their kidneys “pack it in,” says the BBC.
For those brave enough to want to see the rest of the cave, well, you guessed it, you have to dive into that poisonous water and navigate through narrow passageways until you reach air-spaces, called air bells. EcoWatch says this is the most dangerous part of exploring the cave. You are far from the surface, all alone and getting stuck in a narrow tunnel or even worse, getting lost would be terrifying and lethal.
Movile Cave’s unique ecosystem
We have talked about some of the creatures found in the cave, but scientists have found that the further into the cave they go, the worse the air becomes, and yet, the more animals there are. In the lake itself, shrimp and snails scurry around, trying to avoid water scorpions and long-legged spiders. In the air bells, leeches swim across the water preying on earthworms.
On the Earth’s surface, plants use sunlight to take up carbon dioxide and turn it into oxygen and organic compounds. The plants, in turn, use those compounds to feed their roots leaves and stems. Animals then feed on the plants. But in Movile Cave, there doesn’t appear to be a source of food.
In most caves, water dripping down from the surface provides food for cave creatures, and we can see that water in the form of stalactites and stalagmites. Movile Cave has a thick layer of clay above it, which is impermeable to water. This proved to be a mystery which only deepened when the water in the lake was tested for radioactive cesium and strontium.
The 1986 nuclear accident at Chernobyl released a large amount of these radioactive metals into the soil and surface water in the region. However, a 1996 study found that Movile Cave’s lake contained no radioactive elements, leading scientists to believe the lake’s water did not come from above the cave.
An ecosystem dependent on chemosynthetic bacteria
Further testing of the lake’s water showed there were no food particles to be seen. So the big question became, where does the food come from to feed all these creatures? Food comes from a foamy film sitting on top of the lake’s water and on the walls of the cave. This film is like toilet paper, and can even be torn like a piece of toilet paper. It is filled with billions upon billions of bacteria “autotrophs.”
The cave’s ecosystem relied entirely on these chemosynthetic bacteria. They can extract carbon without needing sunlight, with the most numerous bacteria using carbon dioxide while others get their carbon from methane. The bacterial film on the lake’s water and walls of the cave is where all the nutrients enter the cave’s ecosystem and it is the only known example of such a system. The cycle of life can go on as small creatures eat the slime and larger creatures eat the smaller ones. How cool is that?
“These bacteria get their carbon from carbon dioxide just like plants do,” says Boden. “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.”
Movile Cave’s unique ecosystem and creatures could perhaps help us to understand what life was like in the planet’s primordial past, as well as give us some clues to battling greenhouse gasses. In our world’s early years, sunlight was obscured by an atmospheric soup containing carbon dioxide, methane, and ammonia. It is possible that the first living cells were similar to the ones found in the cave.
More exciting is the cave bacteria’s ability to oxidize methane and carbon dioxide, both of them being important greenhouse gasses today. It would be really interesting to find out how these bacteria pull off oxidizing these two gasses and then developing a technology that would be able to break down the two gasses in our atmosphere to more acceptable levels.
