Antarctica's mysterious microfauna

This week, the United States and Great Britain launched a joint project to investigate the Thwaites glacier, whose collapse could trigger rapidly acceleratedsea-level rise. To understand the threat posed by the so-called "doomsday glacier," scientists will head to Antarctica, to see the impact humankind has had on terrains about as remote from civilization as this planet gets. 

Even within the animal kingdom, few make it this far. Whales, seals, sea birds and penguins inhabit the ocean and air around Antarctica or come ashore at certain times of year. But year-round inhabitants of the coldest continent are far harder to spot.

The largest permanent terrestrial creature is a wingless midge that lives in the relatively agreeable climate of the Antarctic Peninsula. Further inland, six-legged springtails are the size of a full stop, just visible to the naked eye. They share their patch with even tinier nematodes, rotifers and tardigrades.

But in this microscopic world, scientists are making surprising discoveries about the richness and diversity of Antarctic life. With the help of ever-more sophisticated DNA sequencing techniques, they have identified at least 15 ecological hotspots.

Library of life

Ian Hogg, a polar ecologist at Waikato University in New Zealand and Polar Knowledge Canada, spent last summer exploring Antarctica's Shackleton glacier in pursuit of a springtail that had been collected there during the 1960s but hadn't been seen since.

Now, its rediscovery means its genetic fingerprint will be added to a growing database of Antarctic life.

"One of the things we've been doing for a while now is to build up a reference library to catalogue what lives where and what their genetic signal is," Hogg told DW. "This will allow us to go to any site, grab a random sample, analyze all DNA in it and to look at all the animals and plants in there by matching DNA in the sample against sequences in the library."

Antarctica's terrestrial fauna spends much of its time hovering in a state of suspended animation, either freeze-dried to a speck, or pumped full of antifreeze waiting for the few days, or even hours, during the Antarctic summer when there is enough liquid water and warmth to reignite their metabolism.

In such conditions, metagenomics – the study of DNA sequences extracted from an environmental sample such as a handful of Antarctic soil – has been a game-changer.

Sub-glacial sanctuaries

Ceridwen Fraser from the Australian National University used molecular genetics to investigate soil samples collected from spectacular ice caves around Mount Erebus, the world's southernmost active volcano.

Like oases in the frozen desert, these caves below the ice are relatively warm and moist, shaped by volcanic steam rising up from vents.

Fraser's tests revealed traces of various mosses, nematodes and springtails, many of which didn't match any known genetic sequence.

Fraser says they could be previously documented species on which little genetic work has been done. "But I also think it is possible that there are species in these Antarctic caves that have adapted to these unique environments and are not found anywhere else," she told DW.

From an ecologist's perspective, Antarctica is like the deep sea, Fraser said. "We've only just scratched the surface of discovering what's there and starting to understand it. It's not at all unlikely that using environmental DNA, we'll stumble on new things."

Her discoveries support the idea that the volcanic caves act as ecological sanctuaries. "We have good evidence that plants and animals have survived in Antarctica for millions of years," Fraser said. "There's not a lot of space for them to live, and there was even less in the past, so these volcanic ice caves would have offered refuge."

Bacterial kingdoms

Fraser's samples were collected by Waikato University microbiologist Craig Cary, who first took a DNA sequencing kit to Antarctica nearly two decades ago to scour the geothermal areas around Mount Erebus for extremophiles – bacteria that thrive in conditions that would kill other organisms.

His focus has since shifted to the arid soils of the McMurdo Dry Valleys, the largest stretch of ice-free land on the continent. Cary teamed up with microbial ecologist Don Cowan from the University of Pretoria, and together they began overthrowing the long-held idea that only a few species of bacteria survive in Antarctica.

Before the arrival of DNA sequencing technologies, microbiologists relied on culture methods and microscopy, which limited discoveries to bacteria that can happily grow in a petri dish. This meant they saw only the tip of an iceberg.

"Considerably less than 10 percent of the microorganisms living in the soil, just in the habitat that we study in the Dry Valleys, have ever been seen growing on an agar plate and studied," Cowan told DW. Genetic methods revealed a far more complex and diverse microbial ecosystem, with many species lying dormant and undetectable by traditional methods.

Race against time

But the exploration of this surprising diversity of life is something of a race against the clock, as human activity changes Antarctica's unique ecosystems, both on land and in the surrounding ocean.

We don't yet know how long the Thwaites glacier will hold out. But smaller icebergs have already succumbed to climate change. Last year, a huge chunk calved off the Larsen C ice shelf, uncovering an area of the ocean floor below that had not seen daylight for 120,000 years.

Marine biologists from the British Antarctic Survey sailed south to capture the diversity of bottom-dwelling marine organisms. But their efforts were thwarted by sea ice and had to be postponed to the next southern summer, by which time some changes may have already taken place.

Ian Hogg has a similar sense of urgency about the conservation of Antarctica's terrestrial ecosystems. "How do you conserve something if you don't know what you've got? And if you don't know what you've got, it's easy to lose it."