After 40,000 years, microbes wake up from thawing permafrost: ScienceAlert

Ancient life has been resurrected from the bowels of a military tunnel that penetrates Alaska’s permafrost.

Some of the thawed microbes from these long-frozen soils have been trapped for 40,000 years. Now they have been awakened.

“These are not dead samples by any means,” said microbiologist and geochemist Tristan Caro, a doctoral student at the University of Colorado Boulder (CU Boulder) during the study.

“They are still quite capable of supporting robust life capable of breaking down organic matter and releasing it as carbon dioxide.”

Related: A vast expanse of the Arctic has turned into a carbon emitter

Caro and her colleagues aren’t breeding undead just for fun.

As our reliance on fossil fuels continues to warm the world, Arctic permafrost – the frozen soil, ice and rocks beneath nearly a quarter of the Northern Hemisphere’s landmass – is melting, releasing the greenhouse gases stored there.

As these layers melt, many microscopic creatures – like those present in the team’s samples – will come to life and, with a new appetite, consume any decaying matter around them. This will release more methane and carbon dioxide into the atmosphere, contributing to climate change.

“This is one of the biggest unknowns when it comes to climate responses,” says Sebastian Kopf, a geomicrobiologist at CU Boulder. “How will the thawing of all this frozen ground, where we know there are tons of carbon stored, affect the ecology of these regions and the rate of climate change?”

Researchers collected frozen samples at the U.S. Army Corps of Engineers’ bizarre Permafrost Tunnel Research Facility, which descends more than 100 meters (350 feet) underground.

Back in the lab, they incubated microscopic life at a cool 39°F and 54°F (3.8°C and 12.2°C), simulating the conditions of an Alaskan summer under climate change.

The microbes grew slowly at first, with some strains replacing only one in 100,000 cells per day. For comparison, most bacterial strains grown in the laboratory tend to completely replace their colonies within a few hours.

But after six months, the microbes in the permafrost took action, as if they were finally convinced to emerge from their frost bed.

This suggests that after periods of heat that melt permafrost, there could be a delay before microbes start emitting significant levels of greenhouse gases. It also suggests that longer, warmer Arctic summers increase the risk of a dangerous emissions feedback loop between humans and microbes.

“There may be just one warm day during the summer in Alaska, but what matters much more is the lengthening of the summer season until those warm temperatures extend into the fall and spring,” Caro says.

These results are important for predicting how microbes and permafrost will contribute to Arctic warming, “particularly as thawing continues in deeper, older permafrost horizons,” the researchers write.

The research was published in Geophysical Research Journal: Biogeosciences.