Scientists say they have solved the mystery of how giant sponges flourish in the deep, icy waters of the Arctic.
Marine sponges survive by feeding on the remains of worms and other extinct animals that died out thousands of years ago, they suggest.
Sponges are very simple ancient animals found in seas all over the world, from deep oceans to shallow tropical reefs.
They have been found living in large numbers and in impressive size at the bottom of the Arctic Ocean.
These massive “sponge gardens” are part of a unique ecosystem that thrives under 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 reach up to a meter in diameter”, he explains.
“This is the first evidence of sponges eating ancient fossil matter.”
By swinging a camera into the depths of the ice, the researchers were able to photograph the collections of sponges that form a garden at the bottom of the sea.
At the time, they were confused about how primitive animals survived in the cold, dark depths, far from any known food source.
More recently, after analyzing samples from the Arctic expedition, they found that sponges were on average 300 years old.
And that these beings survive by eating the remains of an extinct community of animals — with the help of friendly bacteria that produce antibiotics.
“Where sponges like to live, there is a layer of dead material,” says Professor Antje Boetius of the Alfred Wegener Institute in Bremerhaven, who led the Arctic expedition.
“And it finally dawned on us that this might be the solution to why sponges are so abundant, because they can exploit this organic matter with the help of symbiotes.”
The discovery shows that we have much more to learn about Planet Earth and there may be more life forms waiting to be discovered beneath the ice.
“There’s so much alien-like life and especially in the ice-covered seas where we barely have the technology to access it, look around and make a map,” he adds.
But with Arctic sea ice retreating at an unprecedented rate, researchers warn that this once-in-a-lifetime web 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 dramatic decline over the past 30 years, which is consistent with observations of a warming Arctic.
“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 these pressured Arctic seas,” says Boetius.
The study was published in the scientific journal Nature Communications.
