You’ll agree with me that it’s pretty well accepted that life needs a few basic things in order to survive. For most of us, we’d name items like
food, water, and air. If we’re talking about plants, they can skip that food item, since they produce their own but they need light in order to
make that food.
For most organisms, if you took away any of those three legs that support them, you’d end up with a dead organism. Humans, for example,
generally operate on the rule of 3:3 minutes without air, 3 days without water or 3 weeks without food is enough to put a human in grave
danger.
But what if there was an environment that lacked not one, but multiple of these “needed” features for life? Could anything survive there?
That’s the situation with Movile Cave, located in southeast Romania, near the Black Sea. This cave has no light, and it’s been sealed off for
millions of years from the outside world which means that its atmosphere has become drastically different from that of the outside
environment.
No light means no plants, which means no food. A sealed cave means a poisonous atmosphere.
Surely, nothing could be growing in here. Right?
Without Light, Life Still Finds a (Stinky) Way
First, let’s get a basic idea of what the interior of this cave, deep below the surface, is like:
There’s water in the cave, but it’s not dripping down from the ceiling, like in most caves. Most caves get water from rainfall that eventually
makes it’s way down through the soil into the cave but Movile instead gets water from the sandstone base layer, slowly diffusing up into the
cave.
Next, the atmosphere. It’s poisonous, at least to us. It’s less than 10% oxygen and consists mostly of carbon dioxide and hydrogen sulfide.
Finally, and perhaps the most obvious, it’s completely dark. No light gets into the cave.
And yet, there’s still life 48 species have been identified to live in Movile, with 33 of those not being found anywhere else in the world.
And these animals aren’t all closely related or living in harmony, either. Snails, shrimp, spiders, water scorpions, leeches, worms, louses,
and more. All kinds of creepy-crawly bugs, insects and arthropods, feasting and preying on each other.
Where do they get their food, though? The ones that aren’t eating each other what do they live on?
The answer, it turns out, is a very specialized family of bacteria, that float in mats on top of the water in the cave.
These bacteria are in a group known as chemotrophs, which translates to “chemical eaters”. Unlike plants, which are phototrophs (“light
eaters”), these bacteria are capable of using chemical reactions to generate energy, which they use to live and grow.
In the Movile Cave, these bacteria convert sulphide into sulphuric acid, ammonium to nitrate, and the methane gas in the cave into a mix of
waste products, like methanol and other compounds.
This isn’t a skill that’s unique to the cave, by the way, chemotrophic bacteria are found in all sorts of extreme environments. They’re in hot
springs, like in Yellowstone National Park. They’re found around deep-sea vents in the ocean, making use of the heat and chemicals that
stream up from beneath the ocean’s floor. They’re even in the soil of farmlands, converting nitrogen into nitrites and nitrates that become
plant fertilizer.
So, despite the wild environment of Movile Cave, the bacteria that form the basis of the food chain are fairly common, similar to the
bacteria found in other extreme environments.
But the larger organisms that feed on these bacteria? These ones are only found here, in this cave.
The Traits For Living Trapped Underground
If you’re a creature that will only live underground, trapped in a cave, what sort of features are important or unimportant?
Eyes, for example, aren’t important if you’re living in darkness. All of the insects in Movile Cave are blind.
Touch, on the other hand, is more important when you can’t rely on sight. Many of the Movile Cave organisms have grown long feelers,
allowing them to sense rocks or predators, or prey around them.
Colouration isn’t important. Again, in the dark, there’s no need to camouflage, which means that it’s not worth wasting energy to produce
pigment. Nearly all the creatures from Movile are bleached white (if you shine a light on them).
Webs, surprisingly, are important! There aren’t any truly flying insects in Movile (hard to fly if you can’t see where you’re going), but some
bugs do hop or bounce to move around. These bugs get caught in the webs spun by blind spiders.
The insects and arthropods living in Movile Cave are well evolved for their unique environment which means that they’ve been trapped in
this micro-ecosystem for a long time, in order to adapt. These creatures have, through random evolution, selected traits that are useful in
this tiny little location, and practically nowhere else in the world.
If you want to see images of these insects, check out the work of Patrick Landmann, who has taken incredible photographs of these
creatures.
If you want to take a lesson away from Movile Cave, it’s probably best summed up in the words from Michael Crichton’s Dr. Ian Malcolm,
the scientist in the book (and movie) Jurassic Park. “Life finds a way,” he warns the other scientists who think that they can control every
variable in an experiment.
Even in this dark, sealed-off cave, where there’s no light and the very air is toxic, life has found a way to survive and flourish for millions of
years, by some estimates of how long the bugs have been trapped there.
These organisms have developed unique adaptations that aren’t useful anywhere else but provide aid in this dark, sealed environment.
They’ve lost traits that we consider natural (like eyes, or pigmentation) that don’t provide any advantage in the darkness.
Fewer than 100 people have ever explored Movile Cave; it’s difficult to reach, its atmosphere is toxic to breathe for more than a couple of
hours, and there’s not much to see there.
But for the biologists who have visited and collected samples, this “poison cave” has provided an amazing insight into how life can adapt to
extreme environments, surviving in conditions that seem impossible.
Shhhhh…. or maybe its time for … adventures with aliens…? “The Ends of the Earth: Secret Abbys of Movile Cave” and “The Secret
Underworld (Movile sulphur cave life, Romania) [National Geographic Adventures]” movies are right on the corner of the internet shelf.
