Buried in Romania: Forever-Dark Cave Crawling With Life
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It's a scene straight out of a Halloween horror flick: Isolated from the world for millions of years, forever-dark Movile Cave in Dobrogea, Romania is crawling with life. Despite the fact that the cave receives no energy from the sun, a unique community of animals stalks its tortuous inner reaches: hundreds of spiders and other creatures, and previously unknown microbes. Water scorpions, predatory leeches, and troglobites, oh, my!
Funded by the National Science Foundation, a team of biologists from the University of Cincinnati will soon return to the cave to conduct further research. An artificial entrance shaft, created by accident during a construction project, first allowed scientists access to the subterranean system. Biologists found a diverse, and by cave standards abundant, fauna in the dank chambers -- some 47 animal species to date. Thirty of the 47 species were previously unknown.
In a pattern called troglomorphy, all show a reduction or loss of eyes and pigmentation, and enlargement of appendages and what scientists call extraoptic sensory structures, "antennae" of gigantic proportions. The ancestors of some of these species may have become isolated from their surface-dwelling relatives more than five million years ago, when the climate of southern Romania became very dry. Today, these creatures are an underground Addams Family.
Located west of the Black Sea and bordered by the Danube River and the Casimcea Valley, Movile Cave was discovered in 1986. It was not explored, however, until the fall of Romanian dictator Nicolae Ceausescu. Since then, researchers have proved that there are no links between the outside world and the cave's hidden galleries and air bells, or pockets. Cave sediments are also devoid of Cesium radionuclides, significant because surface sediments in Dobrogea contain high levels of these nuclides, due to the 1986 Chernobyl accident.
"So food and bacteria don't come in from the surface," says University of Cincinnati biologist Brian Kinkle. "The sole sources of food appear to be hydrogen sulfide and methane from groundwater trickling through the cave's inner chambers."
Thick deposits of loess -- silt mixed with fine sand or clay -- overlying the cave's limestone surface, and a lack of nutrient-rich surface streams or lakes in the region, indicate that the cave's animal community receives little, if any, organic input from the surface, according to biologist Thomas Kane, also of the University of Cincinnati. "Despite the extreme isolation of the system, which has apparently existed for some time, the huge population sizes of the invertebrate species in the cave suggest a large energy base. And the presence of thick microbial mats in the cave's deeper recesses supports this idea."
Movile Cave differs in two important aspects from other caves: Its waters are much warmer than those of "typical" limestone caves, and are rich in hydrogen sulfide. To find out which strains of bacteria are most important in converting this hydrogen sulfide to a food source, the scientists are studying unusual microbes growing in waterborne mats on the cave's walls, and in its underground lake. Says Luminita Sarbu, a graduate student at the University of Cincinnati, "We developed fluorescent antibodies that bind only with certain strains of bacteria, and used them in the cave samples to see how abundant these bacteria were. We're now checking to see how important a component the bacteria are to life in the cave."
The scientists must take extreme care not to contaminate the cave's fragile environment. Only three people are allowed in the cave at a time, for periods of one hour. Researchers change their clothes upon entering the cave, to avoid bringing in "foreign" microbes.
By returning to Movile Cave, Luminita Sarbu hopes to determine whether stringy filaments she's seen under the microscope are fungi. "Some filamentous bacteria can be as big as fungi, so judging by size alone is not enough." If the suspected fungi turn out to be the real thing, yet more questions will arise. How can the fungi survive when so little organic material exists in the cave? Do they have unique metabolisms, or have they adapted in some way to the scarcity of food?
The answers lie hidden in Movile Cave's black depths, the perfect setting for a Stephen King novel.
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