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University of Cincinnati Biologists Find First Terrestrial Ecosystem That Survives Without Sun's Energy

University of Cincinnati

Cincinnati A team of University of Cincinnati biologists reports in the June 28 issue of Science that an unusual Romanian cave system survives and thrives without the benefit of the sun's energy.

Every other terrestrial or land-based ecosystem known is based on photosynthesis the conversion of solar energy into food. However, a detailed study of Romania's Movile Cave demonstrated that the base of the food web is chemoautotrophic.

Microbes living deep inside the cave's air bells use the energy released by oxidizing hydrogen sulfide to provide food for the cave's numerous and unusual animals. The cave contains 48 species, including 33 which are found nowhere else in the world.

"Movile is the only cave system known that is chemoautotrophically based, and it contains the only known chemoautotrophically based terrestrial community," said Thomas Kane, professor of biological sciences. "We have now shown that chemoautotrophic systems are more widespread than had been thought."

To prove that the food web was based entirely on chemical energy and not solar energy, Kane, doctoral candidate Serban Sarbu and assistant professor Brian Kinkle used a technique known as stable isotope ratio analysis (SIRA). This was the same technique used to demonstrate that the communities living around deep sea vents were chemoautotrophic.

By comparing the distinct ratios of two carbon (12C and 13C) two nitrogen (14N and 15N) isotopes, the researchers were able to trace energy flow through the food web from the microbe producers through the intermediate grazers to the carnivores at the top of the food web.

"All the data show quite clearly that these animals are based on chemoautotrophic carbon production. They don't eat any food that comes from the surface," said Sarbu.

The University of Cincinnati researchers also analyzed the isotope ratios of similar organisms living in other caves and in a nearby well. Again, the data clearly showed that the Movile Cave is unique.

"If you look at other caves based on photosynthetic energy...they're quite distinct. The different caves have very different chemical signatures," said Kinkle.

Sarbu first began exploring the Movile Cave in 1986 following its discovery by Romanian geologist Cristian Lascu. The explorations halted after Sarbu fled the oppression of the Ceausescu regime, resuming in 1990.

The current research is funded by the National Science Foundation with additional support through the Fulbright Program, the National Geographic Society, and the National Speleological Society.

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