Spectacular creatures in a poisonous sulphidic atmosphere – Movile cave, Romania – 5.5 million years time capsule

Only 240 m length and 12.000 square meters, but an epochal discovery made in 1986 in the south-eastern part of Romania by the Romanian researcher Cristian Lascu (geologist, speleologist and photographer). Some geodesic studies for the location of a thermal power station on the surface of an abandoned mining pit at Mangalia, in the south-eastern part of Romania, less than 2 km from the Black Sea, have identified at 6 m deep an underground space that does not communicate with the surface. At that moment, no one imagined the Movile Cave, a small cave with narrow passages covered with clay, but with gorgeous and spectacular labyrinthine galleries, would be considered one of the greatest discoveries of the century that revolutionized the theories of life on Earth.

In a poisonous sulphidic underground atmosphere, the biologists from the Romanian National Institute of Speleology have identified a stable and unique chemoautotrophic ecosystem, completely separated from the terrestrial atmosphere for about 5.5 million years.

The discovery was certified ten years later by NASA researchers who brought to Mangalia an ultra-sophisticated mobile laboratory and a team of scientists who launched a research project in collaboration with Romanian counterparts.

The tests carried out have shown that the water flowing has different chemical composition than the nearby fountains, does not contain neither food particles, nor radioactive isotopes common in the soil of Romania after the Chernobyl accident. The only explanation was the water from the cave isn’t coming from above, so it must be coming from 25,000 years old spongy limestones strata from below. The sulphurous and thermal water (21 degrees Celsius) flows through closed karst channels (Fig.1a), coming along a deep fault, as typical geomanifestation, directly from the depths of the Earth. Or maybe only the hydrogen sulphide (H2S) came from there, being dissolved later in the deep water levels…

Fig. 1 – a) Map of cave; b) The nutritive mat – base for the whole cave trophic chain; c,d) scientist Cristian Lascu, the discoverer of the cave, during the first stages of research

It seems the worse the air gets, the more life there is. The Movile Cave abounds of strange creatures and fungi, adapted to an absolutely particular environment. The scientists have identified 48 species, including 33 found nowhere else in the world. All life is based on a strange frothy foam mat (Fig.1b) of autotrophic bacteria which takes the energy from chemosynthesis (oxidation of sulphur and methane/ ammonium found in the groundwaters). These mat and films full of nutrients are spread over the walls of the cave and floor of the water bodies and represents the food source for other heterotrophic bacteria and fungi. This unique trophic chain is continuing with small insects, pseudoscorpions and other invertebrates (isopods, springtails, woodlice), which are prey of the unique species of larger predators as spiders, snails, leeches, shrimps, centipedes or waterscorpions (Fig.2).

Fig. 2 – a) Cave habitant (photo steemit.com); b) A waterscorpion (Nepa sp.) from Movile (Credit: Thierry Berrod, Mona Lisa Production/SPL); c) Centipede (photo Dustin Main); d) Pseudoscorpion

Just 10% oxygen in the air (rather than the usual 20%), but a lot of hydrogen sulfide (8-12 mg/l), carbon dioxide (2-3.5% – 100 times higher than normal air) and methane (1-2%). “The pool of warm, sulphidic water stinks of rotting eggs or burnt rubber when you disturb it as hydrogen sulphide is given off” (2010, Rich Boden – microbiologist, the 29th person who has seen the cave for scientific purposes). “Sulphuric acid actually erodes the limestone, which is gradually making the cave bigger,” says Boden. “The process releases carbon dioxide, which is why levels are so high.”

Obviously, hypotheses have been issued regarding the origin of these creatures. The theories suggest from the simply entering of the species in the Movile Cave by choice or accidental falls, followed by the adaptation to this specific cave habitat (as the insects are believed to have approached the cave during the Miocene Epoch), to the arriving of different newly colonizing species in various stages of time, maybe due to the terrestrial environmental constraints. The last assumption is sustained by the fact that a species of snail living in the cave has been found to inhabit the cave for slightly more than 2 million years, similar to an ice age period). However, the studies indicate that the bacteria discovered in the cave are very similar to bacteria found elsewhere, but being derived from ancestors well before 5.5 million years ago.

Fig. 3 – Prey and predator in Movile cave: a) Step by step, in the dark; b) Waterscorpion eating a crustacean (Photo geek.com)

To maintain the delicate balance of this unique and fragile ecosystem, the explorations of the cave are strictly regulated and only a few dozen scientists have been allowed to visit one of the most isolated ecosystem on the planet. Not only to conserve a place where we could find out responses to specific questions related to the life on primordial Earth, but also to look for solutions to manage the carbon dioxide and methane (greenhouse gases) presence on the Earth or on other planets, potential future destination for humanity.

But at a distance of only 2 km, on the Black Sea shore, the lovers of Earth mystery can at the same time enjoy scuba diving and observe a typical geomanifestation environment. The sulphurous underground waters of continental karst origin come to the surface through the lines of faults and the channels of the Sarmatian limestones. The submarine sulphurous springs from Mangalia contain the largest diversity of marine habitats from Romania. This Natura 2000 site (ROSCI 0094) includes not only sulphur hydrothermal springs of shallow depth and infralittoral rocks with photophilic algae (Fig. 4a,b), but also meadows with Zostera noltii in fine or muddy sands (Fig. 4c,d) or muddy sands bioturbated by Upogebia.

Fig. 4 – a,b) Yellow-white halos formed by thiophilic bacteria which developed around the sulphurous springs (photos: Adrian Popa); c) infralittoral rocks and photophilic algae (photo – INCDM Archive); d) Zostera noltii and other specific plants in the shallow waters (photo – INCDM Archive)

Shhhhh…. or maybe is 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.

dr. Valentina Cetean
IGR, Geological Institute of Romania


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