Bacteria, fungi, shellfish, and maybe even fish live in Lake Vostok, the buried Antarctic lake that's been likened to habitats that might exist on other planets or moons, a new study says.
But soon after the paper was published and widely reported, other Vostok experts voiced strong skepticism about its conclusions. (Related: "Race Is On to Find Life Under Antarctic Ice.")
Nothing like the kind of multicellular life described in the paper has been identified in Vostok ice cores before, they said, and the paper does not provide the strong scientific support needed to back its extraordinary claims.
Study leader Scott O. Rogers, of Bowling Green State University in Ohio, acknowledged the other scientists' doubts and said he expected it.
He said that his team used a new technique to concentrate and then analyze genetic sequences found in the sample, and that "time will tell if we're right or we're wrong."
The paper, published July 3 in the open-access, peer-reviewed online journal PLoS ONE, identified the genetic signatures of more than 3,500 different life-forms in samples taken from the Vostok ice core 5G, which was drilled by a Russian team, with American and French help, in the 1990s.
The core section that was analyzed came from the U.S. National Ice Core Laboratory in Denver—not from the celebrated column recovered by the Russians in early 2013, a year after their team drilled into the lake for the first time. (Related: "Russian Scientists Breach Antarctica's Lake Vostok—Confirmed.")
The sample studied is from what is called "accretion ice," which freezes on the bottom of the 2.5-mile-deep (4-kilometer-deep) glacier that sits atop the lake, which is roughly the size of Lake Ontario in North America. The accretion ice is formed from the top millimeter of the Vostok water column, which in some places is 2,600 feet (800 meters) deep.
Researchers have previously identified small but predictable numbers of single-celled organisms in various Vostok cores. But the new study's discovery of DNA and RNA sequences from complex organisms is new—and controversial.
A microbe found in a Lake Vostok ice core.
Image from NASA/Photo Researchers
Brent Christner of Louisiana State University, who has also studied Vostok and other Antarctic ice cores, said the presence of such a broad population of multicellular organisms would, if true, represent "a paradigm shift" in how life very deep under ice would be understood. (See "Antarctica May Contain 'Oasis of Life.'")
"It's very difficult to reconcile the diversity reported with the existing body of data on the Vostok ice core," he said, pointing especially to the dearth of food for more complex organisms to live on.
"It will take a lot more evidence before I'm convinced."
And then there's the question of contamination—that the genetic signatures found in the ice core may be from other organisms that accidentally got mixed into the sample.
Though the scientists were careful when transporting the ice, it's still questionable whether the samples are free of contamination, Mahlon C. Kennicutt II, a professor of oceanography at Texas A&M University, noted by email.
"Unfortunately, once the integrity of the samples is called into question, the results will always be suspect, so these results need to be taken with caution and some skepticism," Kennicutt said.
For instance, the Russian team at Vostok has long used kerosene to aid in drilling ice cores, and many have concluded that organisms in that fuel have contaminated the samples—especially the older ones from the 1990s. (Also see "Pictures: 'Extreme' Antarctic Science Revealed.")
Montana State University's John Priscu, a longtime researcher of subglacial Antarctic lakes, made his opinion clear in an email: "They have to stop playing around with kerosene-soaked ice and get a clean sample of bulk lake water before unequivocal conclusions can be made."
In February, Priscu and his U.S. team reported the discovery of microbes hidden under more than a half-mile of ice in Lake Whillans, part of a vast system of lakes and streams deep below the surface of Antarctica.
Study leader Rogers agreed that the contamination issue was a difficult one, adding that it had broken up his collaboration with the leader of the Russian Vostok team, Sergei Bulat.
The Russian scientist has consistently taken the position that the single-celled organisms previously found in Vostok ice were the result of contamination from both kerosene and antifreeze used during drilling.
Reflecting the difficulty of coming to scientific conclusions about Vostok, Bulat surprised his field when he said early this year that the Russian team had found previously unknown bacteria in the Vostok ice that came from the 2012 breakthrough core. (Take an Antarctic quiz.)
But that conclusion was disputed by his own colleagues and has never been reported in a scientific paper.
Rogers and other U.S. scientists have argued that the contamination can be accounted for and that some native Vostok organisms can be identified as such.
Most of the life-forms Rogers found were bacteria. But he believes that multicellular creatures in Vostok—which was part of a temperate environment until 15 to 25 million years ago—could represent extreme adaptations by life-forms that existed in that warmer era.