Beneath some 13,000 feet of Antarctic ice is a world that should be lonely and empty. But, if a new study is correct, this subglacial lake could be teeming with hardy bacteria buried in one of the world’s most unusual environments.
Scientists from Bowling Green State University have recovered more than 3,000 gene sequences – some from complex organisms – from the ice of Lake Vostok, the world’s largest known subglacial lake. If the samples are found not to have been contaminated, the findings could be revolutionary, altering our understanding of life not only on our own planet but on alien worlds.
Lake Vostok lost contact with the atmosphere some 15 million years ago, and is not thought to be a homey place. The coldest natural temperature ever recorded on Earth – minus 126.6 degrees Fahrenheit – was taken on a mountain near the lake. Below the ice, the water is frigid, except around probable hydrothermal vents that bring it to a boil. The weight of the ice pressurizes the water to a lethal 350 atmospheres at the top of the lake, and even more so down below. The lake is completely dark, with few vital nutrients seeping down to its depths.
But scientists have for years suspected that there could be life there. Astrobiologists – scientists who search for alien life – have suggested that organisms plumbed from those extreme conditions could offer models for what we might find on planets, where similarly unforgiving environments might beg of their inhabitants highly adaptive survival mechanisms that look nothing like the biological processes we know.
In 2008, a team led by Scott Rogers, a biology professor at Bowling Green State University, grew about 800 cultures from cells found in Lake Vostok’s ice. Those cultures correlated to about 50 different species and joined a small crop of studies, dating to about 1999, indicating that – improbably – the subglacial lake could have some residents.
"We knew that there was something down there," said Dr. Rogers, in a phone interview.
In his team’s most recent experiment, the results of which are published in PLOS ONE, Rogers and colleagues analyzed two ice core sections drilled from different sections of the lake, one from the southwestern region, which is about 10,000 years old, and one from the deeper mid basin, which is about 5,000 years old.
Scientists found 3,507 unique gene sequences – a stunning number for Lake Vostok – in about 500 milliliters of water taken from the ice cores. About 90 percent of the sequences came from the older, southwestern region, which is shallower and thought to be friendlier to life. The researchers were then able to make taxonomic classifications for about half of those sequences using the public gene bank.
Biologists divide all living things into three domains: bacteria, a type of single-cell microbe called archaea, and complex organisms called eukaryotes. The majority (94 percent) of the identified material was matched to bacteria. Six percent of the sequences matched to eukaryotes, a few of which were multicellular and were unprecedented finds for the hostile lake environment. Two sequences were from archaea.
The other half of the sequenced material from the ice did not match any sequences in the public database. Rogers told the Monitor that this material could be viruses, an area in which the database has little information. Altogether, though, those unaccounted sequences are suggestive of our world's apparent infinite capacity to surprise us, he said.
“Even though there’s a very large number of sequences in the gene bank, it’s still likely less than half a percent of what’s out there,” said Rogers. “It’s an indication of how much scientists still don’t know.”
The suggestion that life could exist in remote and buried Lake Vostok is controversial. The drills that have been sent spinning down into the lake since its discovery in the 1960s have potentially contaminated the ice with kerosene and other nonnative materials, possibly adding a deceptive wealth of bacteria to an otherwise barren, or at least less populous, ice sheet. Studies that have originated from Lake Vostok samples have historically been plagued with doubt and suspicion, especially since proving contamination, or its absence, is difficult.
And some scientists have expressed concern about the sample used in the latest experiment, drilled from the bottom of the lake’s ice sheet in 1998. Contamination could account for the volume and complexity of organisms sequenced from the ice.
“The analyses used accreted ice samples whose integrity has been questioned in the past,” said Mahlon Kennicutt II, a professor of oceanography at Texas A&M University, in an e-mail interview. “The retrieval of theses samples was not designed for the purpose the accreted ice is now being used for, raising questions about the introduction of non-indigenous organisms during retrieval, on site sampling, and transport to the laboratory.”
“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,” he said.
The scientists acknowledge in their paper the dubious record of samples drilled from Lake Vostok, but also say that high-tech steps were taken during the experiment to eliminate contamination.
“Contamination is always an issue. Putting your fingerprint on the ice could introduce more organisms than are actually in the ice itself,” said Rogers. “But I think we’ve controlled for all those possibilities.”
Another controversial point is whether or not there are even more complex organisms in that ice-harbored world. About half a dozen of the bacteria found in the ice are closely associated with fish – so, against all odds, are there fish down there?
"On a scientific basis it is hard to see how [Lake Vostok] is 'teeming with life' – even multi-cellular life, when there is little evidence that the Lake has the requisite energy, nutrients, and/or carbon sources to support such an ecosystem," said Dr. Kennicutt. "Speculating about higher organisms in the lake is fanciful at best and not in sync with our current understanding of the biogeochemical setting of the lake."
Still, other scientists have expressed optimism that fish could survive sealed beneath the ice.
"Until relatively recently the Antarctic continent was farther north with a temperate to tropical climate, so it is highly likely that lots of biota was present as the continent cooled and moved south by processes of plate tectonics," said James Haynes, a professor in the department of environmental science and biology at SUNY Brockport. "The 20+ million years between lake formation and complete ice cover provided a huge amount of time for species to adapt to colder conditions, possibly including living permanently under ice."
He cautioned, however, that there are still serious questions about what exactly the conditions are like beneath the ice and, once that is known, how that life would have adapted to the unusual environment. Only directly sampling the lake water could prove the existence of living fish there, he said.
Rogers, too, is hopeful that fish might be found in Lake Vostok.
"Animal physiologists might say it's impossible for fish to be alive in that lake – but I believe it's possible," said Rogers.