Unexpected Life Found Half a Mile Under an Antarctic Ice Shelf

Written by Dharna Noor & Isaac Schultz on February 20, 2021. Posted in Current News

Back in 2016, a team of marine scientists from around the world traveled to Antarctica to learn about the mysterious ecosystems under its vast ice shelves. One team of geologists was tasked with taking videos from beneath the Filchner-Ronne Ice Shelf, which is on the South Eastern Weddell Sea.

It was a disaster. The scientists drilled through more than half a mile (900 meters) of ice, but a large, gray boulder got in the way of their ability to get a good sample. They brought the footage back to a lab at Cambridge University, yet they were disappointed—they wanted ice shelf sediment to study, not videos of a hunk of rock.

But the biologists back at the Cambridge saw the sample, they were delighted, because the researchers had accidentally come upon an array of strange creatures that appeared to be Antarctic sea sponges, and they had captured the brief tête-à-tête with the unidentified life on a GoPro attached to the borer. The researchers were shocked, because the conditions under the second-largest Antarctic ice shelf aren’t exactly hospitable to most life. Temperatures there stay well below freezing to 28 degrees Fahrenheit (minus-2.2 degrees Celsius), and it’s constantly dark. Their findings are documented in a new study out Monday.

“It’s kind of like finding a bit of the rainforest in the middle of the Sahara,” Huw Griffiths, a marine biologist with the British Antarctic Survey who led the observation of the animals, said. “It’s the wrong place for that thing.”

“This finding goes against what we expected to see this far under the ice shelves,” he added.

The world beneath the ice is a dynamic, if inhospitable environment. Rocks lodged on the underside of massive tranches of ice can fall off as the sheets shear off one another, causing them to fall through the water, spelling danger for human submersibles. But such a “dropstone” has become a home for a number of species, some suspected to be Antarctic sea sponges, as well as other animals with even more uncertain identities.

Even more incredibly, the lab scientists immediately recognized that the animals were filter feeders, which eat by straining suspended matter and food particles from water. But the sponges had been living 162 miles (260 kilometers) away from the open ocean where that food must have been coming from. They couldn’t have possibly traveled to find food from other sources, because they were attached to the boulder with small, fleshy stems.

“We expected to find mobile animals like fish or crustaceans that can travel around to find the small amounts of food available,” Griffiths said. “The animals in the video are attached to the rock, so they cannot move. This means that they must wait for food to come to them!”

Griffiths is the lead author of the study on these shocking findings, published on Monday in Frontiers in Marine Science. It’s the first-ever record of a community of animals living on a hard surface underneath an ice shelf, and it defies all theories of what kinds of life can survive in these extreme conditions. Griffiths and his team still can’t quite figure out how exactly these animals have been managing to obtain enough food to stay alive. They hope to learn more about the bizarre creatures.

“Although it is based on limited observations, it’s an amazing finding that is an important piece to the puzzle about Antarctic sponges,” César Cárdenas Alarcón, a biologist with the Chilean Antarctic Institute who was not affiliated with the recent paper, wrote in an email. “This work also highlights the importance of developing more interdisciplinary research cruises to improve our understanding of these rare communities, and also to understand potential scenarios as ice shelves collapses are expected to increase as the warming keeps affecting the Antarctic.”

The animals’ existence may have some biologists revisiting the snowball Earth hypothesis, which holds that complex, multicellular life couldn’t get kickstarted until the planet got out of a frigid phase (one that puts more recent ice ages to shame) over 600 million years ago. As extreme as their environments are, Griffiths pointed out, these enigmatic creatures are making it work. To learn more will take some scheming, though.

“To answer our questions, we will have to find a way of getting up close with these animals and their environment, and that’s under 900 meters of ice,” he said. “This means that, as polar scientists, we are going to have to find new and innovative ways to study them and answer all the new questions we have.”

The new findings show just how much scientists are still learning about the parts of Earth that are usually hidden far from human eyes. As the study notes, though, the window of opportunity to study these ecosystems may be closing. Because waters are warming, many ice shelves in the Antarctic are at risk of collapsing into the sea. That includes the one that the sponges live under, the Filchner-Ronne Ice Shelf. If that shelf collapsed, it’s not clear that the newly discovered, enigmatic animals would survive long enough for scientists to figure them out. They’re just one small part of the vast natural world that we stand to lose due to the climate crisis.

“Biologists like to think we know how everything works,” Griffiths said. “When somebody shows you something that completely goes against everything we know, that gets you kind of excited about it anyway.”

More at earther.gizmodo.com

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