Ancient Fossilized DNA Found in Subglacial Lake Sediment

After studying samples of subglacial lake sediments, the British Antarctic Survey has found the first living evidence of diverse lifeforms that have thrived beneath the ice in lakes buried nearly 100,000 years ago.

By the end of the last Ice Age, Lake Hodgson on the Antarctic Peninsula was covered by more than 1,300 feet of ice. But as time passed, the ice receded. Lake Hodgson is now considered to be an emerging subglacial lake, covered by about 12 feet of ice, which is thin enough for researchers to drill through and collect samples from the lake bottom.

The mud at the bottom of the lake is like a time capsule, having microbes that have lived there for millennia. The top layers of sediment contained microbes currently or recently living in the lake. But as the researchers drilled deeper they obtained sediment samples with DNA from microbes that most likely date back almost 100,000 years.

"What was surprising was the high biomass and diversity we found. This is the first time microbes have been identified living in the sediments of a subglacial Antarctic lake and indicates that life can exist and potentially thrive in environments we would consider too extreme," said lead study author David Pearce, who was with the British Antarctic Survey during the research period and now work at University of Northumbria.

"The fact these organisms have survived in such a unique environment could mean they have developed in unique ways which could lead to exciting discoveries for us. This is the early stage and we now need to do more work to further investigate these life forms," Pearce said.

Among the microscopic discoveries in the lake sediment were ancient microbes, the fossilized DNA of which revealed a broad range of microbial species able to live in extremely harsh environments.

"One DNA sequence was related to the most ancient organisms known on Earth and parts of the DNA in 23 percent has not been previously described," the British Antarctic Survey wrote in a statement. "Many of the species are likely to be new to science making clean exploration of the remote lakes isolated under the deeper parts of the ice sheet even more pressing."

Unraveling the clues wrapped up in these extreme microbial lifeforms may lead to new insights into how life might survive on other planets.

The research is published in the journal Diversity.