Scientists say they have solved the mystery of how giant sponges thrive in the deep icy waters of the Arctic.
They suggest that sea sponges survive by feeding on the remains of worms and other extinct animals that died thousands of years ago.
Sponges are very simple ancient animals found in seas all over the world, from the depths of the oceans to the shallow tropical reefs.
They are found living in great numbers and of impressive size on the bottom of the Arctic Ocean.
These massive “sponge gardens” are part of a unique ecosystem that thrives beneath the ice-covered ocean near the North Pole, says Teresa Morganti of the Max Planck Institute for Marine Microbiology in Bremen, Germany.
“We found huge sponges – they can be up to a meter in diameter,” he explains.
“This is the first evidence that sponges eat ancient fossil material.”
The Arctic is one of the regions most affected by climate change – Image: Getty Images via BBC
By swinging a camera deep in the ice, the researchers were able to photograph the groups of sponges that make up a garden on the sea floor.
At the time, they were confused about how primitive animals survived in the cold and dark depths, far from any known food source.
Recently, after analyzing samples from the Arctic expedition, they found that sponges were, on average, 300 years old.
And that these organisms survive by eating the remains of an extinct community of animals – with the help of friendly bacteria that produce antibiotics.
“Wherever sponges like to live, there is a layer of dead material,” says Professor Antjee Boetius of the Alfred Wegener Institute in Bremerhaven, who led the Arctic expedition.
“And it finally dawned on us that this might be the answer to why sponges are so abundant, because they can exploit this organic matter with the help of symbionts.”
Sponges act as ecosystem engineers, keeping the environment healthy – Photo: Alfred Wegener Institute
The discovery shows that we have a lot to learn about planet Earth and there may be more life forms waiting to be discovered under the ice.
“There’s a lot of alien-like life out there, especially in ice-covered seas where we barely have the technology to reach for it, look around, and map it,” he adds.
But as Arctic sea ice is retreating at an unprecedented rate, researchers warn that this once-in-a-lifetime network is under increasing pressure from climate change.
According to scientific measurements, both the thickness and extent of summer sea ice in the Arctic have shown a significant decrease over the past 30 years, which is consistent with observations of Arctic warming.
“With sea ice cover rapidly declining and the ocean environment changing, a better understanding of hotspot ecosystems is essential to protect and manage the unique diversity of compressed Arctic seas,” says Boetius.
The study was published in the scientific journal Nature Communications.
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