Giant sponges feeding on fossils discovered in deep Arctic waters

Scientists from Bremerhaven, Bremen and Kiel discovered a surprisingly rich and densely populated ecosystem on the peaks of extinct underwater volcanoes in the Arctic deep sea. These were dominated by sponges, growing there in large numbers and to impressive size. (Photo: Alfred-Wegener-Institut / PS101 AWI OFOS system)

Deep beneath the ice-covered Arctic Ocean, scientists have made an unusual discovery.

With little to no light, huge sponge gardens appear to survive and even thrive on the remains of extinct fauna.

Found on the tops of extinct underwater volcanoes, these more than 300-year-old sponges seem to share the site with other organisms that contribute to their development.

“Our ana­lysis re­vealed that the sponges have mi­cro­bial sym­bionts that are able to use old or­ganic mat­ter,” explains first-au­thor Teresa Mor­ganti, sponge ex­pert from the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy in Bre­men.

“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.”

This is a unique eco­sys­tem. We have never seen any­thing like it be­fore in the high Cent­ral Arc­tic.Antje Boe­t­ius, chief sci­ent­ist of the ex­ped­i­tion

Researchers discovered this unexpected oasis under the ice during an expedition to the region aboard the renowned polar research vessel RV Polarstern between September and October 2016. Their findings were published in the journal Nature Communications.

On average, the sponges are 300 years old, many are even older. They accommodate a complex community of microorganisms in a symbiotic relationship, which contributes to the health and nutrition of the sponges.
(Photo: Alfred-Wegener-Institut / PS101 AWI OFOS system)
Feasting on the dead

Considered one of the most basic forms of animal life, sponges are found all over the world, from shal­low trop­ical reefs to the arc­tic deep-sea.

Scientists have long known that these animals can host a complex community of microorganisms in a symbiotic relationship. But in this case, they wanted to understand what these microorganisms were feeding on.

By analyzing images captured by a towed camera and sonar system, as well as samples collected during the expedition, they discovered that thousands of years ago, substances seeping from the interior of the seabed fed a rich ecosystem, supporting a wide variety of animals.

When they died out, their remnants remained. They now form the basis of this unexpected sponge garden.

“The mi­crobes have the genes to di­gest re­fract­ory par­tic­u­lates and dis­solved or­ganic mat­ter and use it as a car­bon and ni­tro­gen source, as well as a num­ber of chem­ical en­ergy sources avail­able there,” explains Ute Hentschel from the GEO­MAR Helm­holtz Centre for Ocean Re­search in Kiel, who car­ried out the mi­cro­bi­o­lo­gical ana­lyses with her team.

The mi­crobes have just the right tool­box for this hab­itat. Ute Hentschel

In turn, sponges play an architectural role by producing spicules that form a carpet on which they crawl. This can further facilitate local settling of particles and biogenic materials and thus create a food trap.

The Alfred Wegener Institute’s Ocean Floor Observation System (OFOS), operated from the research icebreaker POLARSTERN, depicted a community of many thousand sponges, ranging in diameter from 1 to 50 centimeter, so dense it almost covered Langseth Ridge’s upper peaks.
(Photo: Alfred-Wegener-Institut / PS101 AWI OFOS system)
A unique discovery

What’s really special about this ecosystem is its uniqueness.

“Primary pro­ductiv­ity in the overly­ing wa­ter provides less than one per­cent of the sponges’ car­bon de­mand,” explains Antje Boe­t­ius. “Thus, this sponge garden may be a tran­si­ent eco­sys­tem, but it is rich in spe­cies, in­clud­ing soft cor­als.”

Dr. Ana Riesgo Gil, a specialist in sponges at the British National Museum and who was not involved in this study, said in a press release that “there could be more sites like this to be found”.

“These sponges are pretty well adapted to the deep sea, so I don’t think this feeding is necessarily limited to these individuals and could be extrapolated to other areas where there were formerly seeps.”

This is the first time scientists have discovered similar sponge-like soil in the Arctic. They now stress the importance of further studying this environment in order to better protect “the unique diversity of these Arctic seas under pressure” from climate change.

Related stories from around the North:

Arctic: Arctic Report Card 2021: Sea ice changes, rain on Greenland ice sheet among dramatic changes in North, Eye on the Arctic

Canada: Climate change could mean more wildlife disease in the Arctic, researchers say, CBC News

Finland: Temperatures headed toward -40C in Finnish Lapland, Yle News

Greenland: Blog: Radical Arctic warming – rain, rain, here to stay?, Marc Lanteigne

Russia: Russia’s new North Pole platform soon ready to move into ice, The Independent Barents Observer

Sweden: January temperatures about 10°C above normal in parts of northern Sweden, says weather service, Radio Sweden

United Kingdom: Meet the five experts who just received the British Polar Medal, Eye on the Arctic

United States: Scientists warn of Arctic microbial threats induced by climate change, Eye on the Arctic

Mathiew Leiser, Eye on the Arctic

Né dans le sud de la France d'une mère anglaise et d'un père français, Mathiew Leiser a parcouru le monde dès son plus jeune âge. Après des études de journalisme international à Londres, il a rapidement acquis différentes compétences journalistiques en travaillant comme journaliste indépendant dans divers médias. De la BBC à l'Agence France Presse en passant par l'agence d'UGC Newsflare, Mathiew a acquis de l'expérience dans différents domaines du journalisme. En 2019, il décide de s'installer à Montréal pour affronter les hivers rigoureux et profiter des beaux étés mais surtout développer son journalisme. Il a rapidement intégré Radio Canada International où il s'efforce de donner le meilleur de lui-même au sein des différentes équipes.

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