biology zoology blog benno meyer rochow chemotrophy cave movile

A Chemotrophic Ecosystem

The wonders of Romania’s “Movile Cave”

Most people would have been taught that life on Earth depended entirely on the sun and the green plants. The latter with their ability in the presence of chlorophyll and light to turn the inorganic molecules CO2 and water into organic carbohydrate (known as photosynthesis), are said to be the basis of the food chain for all animals A few people, however, may also have been taught that there is an alternative to photosynthesis, namely chemosynthesis and that this gave rise to a food chain, for example near hydrothermal vents, not based on green plants and sunlight, but on thermophilic bacteria that use hydrogen and sulphides to build organic material and release methane. But deep sea hydrothermal vents are not the only places where chemosynthetic activity leads to a food chain. The so-called “black layer” a few centimeters below the surface of intertidal mudflats is also a place of chemosynthesis, but the most amazing place is “Movile”.

Movile is a cave in southern Romania discovered 5 years before the amazing find of Oetzi, the iceman in the Tyrolean Alps, and described as a “Subterranean Galapagos”. Of course, iceman and Movile have nothing at all to do with each other, except that I think they were both discoveries that amazed me tremendously. Movile was cut off from the rest of the world for 5.5 million years and although caves generally often seem to share characteristics like isolation, limited size, etc. with islands, this is especially true with regard to Movile. Here in this cave oxygen is in very short supply, but there is a small water-filled pond in which bacteria live that can synthesize organic molecules with the CO2 from the air and the energy obtained from sulphur compounds in the water that the bacteria can utilize. Spongy layers of bacteria and fungi, containing methane, float on the surface of the water and provide both aquatic and terrestrial inhabitants of the unique cave with nutrition.’

However, as with terrestrial food pyramids based on the photosynthetic activities of green plants, there are in the Movile Cave the producers (the chemosynthetic bacteria), and then the primary, secondary as well as tertiary consumers. In the cave pond there are blind little shrimps, roundworms, flatworms and snails, some isopods and microscopic consumers like rotifers (often referred to as ‘wheel animals’) feeding off the bacteria, but there are also blind predators like a reddish leech and a water scorpion (an insect) that prey on the primary consumers. The top predator is undoubtedly the water scorpion.

In the terrestrial environment of this unique cave, the top predators are a pale centipede and four species of cave spiders that feed on tiny pseudoscorpions, beetles, terrestrial isopods and some insects (and in the case of the spiders on each other). Altogether at least 40 new species have been identified after the cave inhabitants were scientifically assessed for the first time following the cave’s discovery. An entire ecosystem, closed for millions of years to outside sources of organic materials, a system that evolved a diverse community of organisms in perpetual darkness: it is something so incredible it’s hard to imagine and has been termed a subterranean Galapagos and a time capsule. All of the species are endemic (occurring nowhere else) and apparently, many of the species found in the cave are phylogenetically linked not to present-day Romanian species outside the cave, but to organisms that lived in the region five million years ago when the local climate was tropical. A time-capsule, indeed.

The big question is: are there other, similar places to the Movile Cave in the world? I would be surprised if there aren’t any others, but to discover them won’t be easy, as equipment to specifically locate such underground places with low oxygen, high CO2 and methane and sulphur-containing water is not available. But then again, there’s also just one Galapagos and maybe Movile Cave is indeed the one and only on Earth.

© Dr V.B. Meyer-Rochow and, 2020.
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