Culture

The Sponge Grounds of the Arctic

Feeding on the remnants of extinct fauna beneath the Arctic Ocean , sponges – masses of them.

The dense sponge grounds discovered in the Arctic deep sea on the northerly Langseth Ridge seamount structure represent an astonishingly rich ecosystem, demonstrating the ability of sponges and associated microorganisms to exploit a variety of refractory food sources including fossil seep detritus. Image credit: Alfred-Wegener-Institut / PS101 AWI OFOS system

Scientists from Bremen, Bremerhaven and Kiel in collaboration with international partners have discovered surprisingly rich and densely populated ecosystem on the peaks of extinct underwater volcanoes,

These hotspots of life were dominated by sponges, growing there in large numbers and to impressive size.

Antje Boetius, is chief scientist of the expedition, 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, Helm­holtz Centre for Po­lar and Mar­ine Re­search.

He said:

“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,”

Teresa Morganti, sponge expert from the Max Planck Institute for Marine Microbiology in Bremen was able to identify how sponges adapt to the most nutrient-poor environment. Morganti explained:

“Our analysis revealed that the sponges have microbial symbionts that are able to use old organic matter. 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.”

Thousands of years ago, substances seeping from the seabed’s interior were supporting a rich ecosystem, home to a variety of animals. When they died out, their remnants remained. Now these form the base of this unexpected sponge garden.

The scientists also showed that the sponges act as ecosystem engineers: They produce spicules that form a mat on which they crawl. This may further facilitate the local settling of particles and biogenic materials. The sponge holobionts can tap into this detrital matter, thus creating their own food trap.

Langseth Ridge is an underwater mountain range not far from the North Pole that sits beneath the permanently ice-covered water’s surface. There, sponge biomass was comparable to that of shallower sponge grounds with much higher nutrient input.

The Arctic is one of the most affected regions by climate change.

The close cooperation of scientists from different institutions, including the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy, the Al­fred We­gener In­sti­tute and GEOMAR, enabled a comprehensive understanding of this surprising hotspot of life in the cold deep.

Antje Boetius, said:

“With sea-ice cover rapidly declining and the ocean environment changing, a better knowledge of hotspot ecosystems is essential for protecting and managing the unique diversity of these Arctic seas under pressure.”

The study is published in the journal Nature Communications: Giant sponge grounds of Central Arctic seamounts are associated with extinct seep life