Antarctica is a relentlessly icy place, with estimates placing the amount of exposed land on the continent at less than one percent of its total surface. During glacial periods, the ice even expanded further—to the point where the edges of the continent's ice sheets extended far out into the ocean.

Yet somehow, life exists on Antarctica. And not just microbial life; there are insects and worms present, too. How have they survived the intensely icy conditions on the continent? A new paper suggests that volcanoes could be the key to life's persistence in our planet's deep south.

Seeking refuge

One of the researchers behind the new work, Ceridwen Fraser, has an ongoing interest in the idea of what are termed "refugia." These are locations where, due to quirks of geography and local climate, life can ride out otherwise harsh conditions that would extinguish it in the surrounding terrain. Once the conditions become more conducive to life—the glacial period ends, for example—the organisms in the refugia spread out and repopulate a wider area.

But where do you find a refugia on a continent like Antarctica, where conditions push life to its edges even under a warm, hospitable climate like today's? Fraser's past work suggests volcanoes might provide a more promising habitat. As in the ocean, volcanic vents could provide chemical energy that bacteria harvest to provide the base of a food chain. But in Antarctica, they can provide something equally critical: warmth. Unlike ocean vents, Antarctica's volcanic vents can be close enough to the surface to allow photosynthetic organisms to thrive.

In an earlier study, Fraser and some collaborators looked at maps of Antarctica's biodiversity. They found that the regions with the most species were centered on geologically active terrain. This supports the idea that volcanic activity creates refugia, allowing life to survive and spread back out when conditions allow.

In a follow-up to that work, Fraser has gone to Antarctica and obtained samples at the sites of volcanic vents. In some cases, these vents are ice free, allowing soil samples to be taken from the surface. In others, the vents are sub-glacial and have created an extensive network of ice caves. Past work at these sites has suggested the presence of microbes and fungi.

Life on ice

In this case, the researchers did a broad search for DNA that included looking for bacteria, plants, and animals. The exposed surface sites turned out to be rich in green algae, and these sites even had evidence of a more complex land plant, likely a moss (the DNA was a match to bryophytes). One animal showed up at one of the surface sites, based on DNA with a sequence closest to arachnids.

Many of these same organisms showed up in some of the ice cave systems the team looked at. Although six of the nine ice caves were devoid of DNA, one contained plants, and three of them contained some algae. The arachnid-like DNA showed up in one of the caves, as did DNA from a type of insect called a springtail. Two distantly related groups of worms also appeared to be present.

Overall, the team suggests that these are likely an underestimation of the biological diversity found in the caves, as they were only able to take samples from a small area inside the ice cave.

While geologically active regions can provide refugia during glacial periods, most individual vents have lifespans that are far shorter than the tens of thousands of years that ice dominates. But the researchers note that there are often complex networks of ice caves that link multiple vents. So, it's possible that cave networks could persist even as individual sources of steam and hot air come and go.

Ultimately, this is something that should probably be independently verified, since contamination can easily trip up the most careful of scientists when it comes to small quantities of DNA. And it would be good to confirm that there are actually living organisms down in these caves, since DNA could probably persist for many thousands of years in the icy conditions of Antarctica, long after the creature that carried it has died.

But the idea of a volcanic refugia is an important one, since it could provide a model for how life might survive elsewhere in our Solar System or how it made it through planet-wide freezes like the ones that happened in Earth's distant past. This work definitely seems to be worth a follow-up.

Polar Biology, 2017. DOI: 10.1007/s00300-017-2198-9 (About DOIs).