Sprawling sponge gardens found deep beneath the Arctic sea ice
Underwater cameras revealed expansive sponge gardens clustered over extinct underwater volcanoes, called seamounts, along the ocean floor.
In order to survive, these largely 300-year-old sponge communities feed off of the fossilized remains of now-extinct animals and fauna. Those creatures likely once relied on the heat and nutrients supplied by the volcanic activity several thousand years ago.
While sponges may seem like a simple form of life, they have persisted for millions of years and can be found across the global ocean, from the tropics to the polar regions, with this latest discovery being the most northern location to date, according to the researchers.
A unique discovery
The central Arctic Ocean, located at the top of the globe, is one of the most remote places on Earth. Few vessels have ever trekked to this area because it’s always covered in ice, but heavy icebreaker ships have managed to explore it.
When the scientists deployed their Ocean Floor Observation Bathymetry System to peer with cameras and sonar beneath the ice, they found an unexplored ecological community. Because of the continuous ice cover, there are few nutrients or food sources.
Finding the sponge community was a complete surprise, according to study author Antje Boetius, chief scientist of the expedition. She is also the head of the Research Group for Deep-Sea Ecology and Technology at the Max Planck Institute for Marine Microbiology and director of the Alfred Wegener Institute at the Helmholtz Centre for Polar and Marine Research.
The sponges vary in size from a few millimeters at the smallest and up to a meter (3.3 feet) in diameter at the largest, with the average measuring about 20 to 30 centimeters (8 to 12 inches) across.
Within the sponges are communities of microbial bacteria. They form a symbiotic relationship because the bacteria help break down the ancient leftovers so the host sponges can obtain nutrients from them.
“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,” said first study author Teresa Morganti, a sponge expert from the Max Planck Institute for Marine Microbiology in Bremen, Germany, in a statement.
In turn, the microbes can dissolve the organic matter on the ocean floor and use it as a source of carbon and nitrogen and chemical energy.
The sponges are also the architects of their own ecosystem, producing spicules, or structural elements that form a mat on which they can crawl.
“Sponges play an important role in nutrient and matter cycling by filtering large volume of water,” Boetius and Morganti wrote in an email.
“Sponges are capable of filtering suspended matter from…
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