Life found deep beneath Antarctic ice shelf

By Angela Heathcote 16 February 2021
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Deep below the Filchner-Ronne Ice Shelf of the Weddell Sea scientists have found a community of sponges thriving on a boulder.

Around 900 metres beneath a floating Antarctic ice shelf and 260 kilometres from open water scientists have made a shocking discovery. 

The British Antarctic Survey was collecting sediment cores from the Filchner-Ronne Ice Shelf situated in the Weddell Sea when it came across a community of sea sponges thriving on a boulder. 

The discovery rewrites previous understandings that purport that life would become less prevalent the further you travelled beneath the ice shelf from open water. 

Marine geoscientist Alexandra Post of Geosciences Australia, the only Australian to work on the paper describing the new findings, published today in the journal Frontiers in Marine Science, says she’s amazed by the discovery. 

“This is the first time we’ve actually seen a rock beneath an ice shelf,which means there’s opportunities for different types of organisms to colonise that part of the seafloor.”

“The other surprising thing is that it was dominated by these organisms that are actually stuck to the rock. That means they can’t go in search of food and the food has to come to them. So, these sponges are sitting there passively on this rock waiting for food to arrive, and that’s challenging at the best of times in Antarctica…so it’s really quite incredible that they can exist.”

Related: Heck no: the giant Antarctic sea spider 

Lead author Huw Griffiths of the British Antarctic Survey called on Alexandra to give her opinion on what exactly they’d found as she has the most experience with marine organisms beneathAntarctic ice shelves. Alexandra’s work on species found beneath the Amery Ice Shelf of East Antarctica was of particular interest.

“We found organisms such as sponges and filter feeders that were fixed to the seafloor and were feeding on food particles from the water column,” she says. “That was the first evidence that those kind of communities could live far from open water, however, the difference to this study is that as we went further from open water on the ice shelf – about 200km from open water – all we were finding were mobile organisms, such as krill and some jellyfish, which had a better chance of finding food. 

“The understanding that we had was that if you’re 260km from open water you might be lucky to see a fish, jellyfish or worm but that’s probably all you’re going to see, so it was a huge surprise to see these sponges.”

The surveyors were only able to capture images of the sponges, rather than taking any samples, meaning the scientists are unsure whether the sponges are a new species. Without sample material it’s difficult to answer the bigger questions, such as what the sponges are eating. 

“They may be feeding on ancient organic matter coming from the bottom of the ice shelf or they may be relying on this long transport of food from open water,” Alexandra says.

“I’d also like to know how the sponges got there in the first place. These organisms can survive in extreme conditions and have some amazing adaptations. It blows me away that they can do that and it gives me hope that life is more resilient than we anticipate.”

Conducting scientific research in these harsh environments is difficult and expensive, but Alexandra is hopeful that technology will overcome the logistical challenges. 

“There’s a good reason why there’s only been 10 bore holes drilled in Antarctic ice shelves,” she says. “I’m hoping autonomous technology will enable us to access these areas in new ways, but at the moment it’s difficult because they need a GPS signal, and under hundreds of metres of ice that’s just not possible. But as technology improves, we’ll be able collect those organisms and that’ll be exciting.

“It’s the last great frontier, there’s so much we don’t know. It’s one of the least understood habitats on Earth. You never know what you’ll find. We always come back with more questions than answers.”