Deep beneath the Arctic Ocean on the peaks of extinct underwater volcanoes, scientists have discovered vast gardens of sea sponges that survive by feeding on the fossils of extinct animals that perished thousands of years ago.
The new discovery of fossil-munching sponges is like nothing scientists have ever seen before. Reporting the new research in the journal Nature Communications, the international team of scientists explained that this find helps to solve the mystery of how animal life can survive and thrive under the ice-covered Arctic Ocean where typical food sources can’t reach.
"Thriving on top of extinct volcanic seamounts of the Langseth Ridge we found massive sponge gardens but did not know what they were feeding on," Antje Boetius, chief scientist of the expedition from Max Planck Institute for Marine Microbiology, said in a statement.
To find out how they were surviving, the team took samples of the sponges taken from the Langseth Ridge - an underwater mountain range not far from the North Pole - and closely looked at the distribution of the sponge gardens on the seafloor. Chemical processes going on within the sponges showed that they were, rather bizarrely, getting their food from fossilized tubes of worms and the hardened detritus of other extinct animals.
"Our analysis revealed that the sponges have microbial symbionts that are able to use old organic matter," explained Teresa Morganti, first-author of the study and sponge expert from the Max Planck Institute for Marine Microbiology. "This allows them to feed on the remnants of former, now extinct inhabitants of the seamounts, such as the tubes of worms composed of protein and chitin and other trapped detritus."
However, the sponges need some help to chomp on fossils. Sponges are considered to be one of the simplest forms of animal life — despite their appearance, they are animals, not plans or fungi — but they maintain a complex symbiotic relationship with bacteria that live within them.
These bacteria are provided with a home and in return pay their “rent” by pumping out antibiotics, which help the sponges’ health. It turns out, the microbes also help out the sponges by digesting and dissolving fossils' super-tough material, freeing it up as food for the sponges.
“This is a unique ecosystem," concluded Boetius. "We have never seen anything like it before in the high Central Arctic. In the study area, primary productivity in the overlying water provides less than one percent of the sponges’ carbon demand. Thus, this sponge garden may be a transient ecosystem, but it is rich in species, including soft corals."