A smorgasbord of microbes feasts on a banquet of fresh seafloor rock.

A research team has found seafloor microbes--growing without light and eating fresh volcanic rocks--that are flourishing with greater abundance than most scientists thought possible. The bacterial communities in oceanic crust were as fertile and prodigious as those found in soil on farms.

"We were truly shocked to find microbial life thriving at the levels we observed," said Cara Santelli, a recent graduate of the MIT/WHOI Joint Program and lead author of a study published May 28 in the journal Nature.

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Santelli conducted the research with geochemists Katrina Edwards (University of Southern California) and Wolfgang Bach (University of Bremen, while all three were at Woods Hole Oceanographic Institution, as well as collaborators from Western Washington University, the Marine Biological Laboratory, and Scripps Institution of Oceanography.

"Theoretical research by Edwards and Bach suggested that life could exist in such a dark, cold, and rocky environment," Santelli said. "The objective of our project was to provide tangible evidence. Not only was the biomass in seafloor lava greater than in the overlying seawater, but the bacterial diversity was significantly greater than we could have imagined."

The findings raise new questions about the evolution of life on the seafloor and on Earth.

"We are just beginning to scratch the surface," Santelli said. "What role does this microbial community play in global ocean chemistry? What sort of metabolism is needed to live in and dominate this environment? And what exactly are these microbes doing down there?"