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article imageScientists find sponges living under Antarctic ice shelf

By Karen Graham     Feb 16, 2021 in Science
The accidental discovery of strange life forms on a boulder beneath the ice shelves of the Antarctic has confounded scientists with the British Antarctic Survey (BAS).
The discovery of the life-forms growing on a boulder far beneath the ice in the Filchner-Ronne Ice Shelf, located in the southeastern Weddell Sea, came as a surprise to the the team of geologists, drilling through the ice to collect sediment samples.
The BAS survey team was drilling through 900 meters (2,953 feet0 of ice, and it's important to note that their location was 260 kilometers (162 miles) away from the open ocean, under complete darkness and temperatures of -2.2 °C. (28 °F).
Very few animals have ever been observed in these extreme conditions because they are so far from sunlight and any obvious source of food. The discovery of the unexpected life forms found by the scientists is documented in the journal Frontiers in Marine Science, published this week (15 February 2021).
Figure 1. Antarctic ice shelf borehole locations with seafloor images. Details for each location can...
Figure 1. Antarctic ice shelf borehole locations with seafloor images. Details for each location can be found in Table 1. New records with life present from this study are marked with a star, boreholes where life was observed with a black circle and where no life was observed or reported with a white circle.
Huw James Griffiths et. al.
An accidental discovery
Dr. James Smith, a geologist at BAS, was part of the drilling team. He says: “We were expecting to retrieve a sediment core from under the ice shelf, so it came as a bit of a surprise when we hit the boulder and saw from the video footage that there were animals living on it.”
CNN reports that the video showed a collection of stationary animals — sponges and possibly several previously unknown species, attached to the boulder. Marine biologist Huw Griffiths, the lead author of the new study documenting the discovery, said "It's about 160 kilometers (524,934 feet6) further under the ice shelf than we had ever seen a sponge before."
“Our discovery raises so many more questions than it answers, such as how did they get there? What are they eating? How long have they been there? How common are these boulders covered in life? Are these the same species as we see outside the ice shelf or are they new species? And what would happen to these communities if the ice shelf collapsed,?” Dr. Griffiths wonders.
Breaking all the rules
The study has a very appropriate title - "Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Beneath an Antarctic Ice Shelf."
What the team found is the first-ever record of a hard substrate (i.e. a boulder) community deep beneath an ice shelf. It just was not expected to be found in such an extreme environment.
A sessile Benthic community is a community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. That they were found so deep under the ocean is not that unusual because some organisms have adapted to deep-water pressure.
Because light is absorbed before it can reach deep ocean-water, the food source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. The researchers note that given the water currents in the region, they calculate that this community may be as much as 1500 km upstream from the closest source of photosynthesis.
So the big question is this: What are the organisms using as a food source? Griffiths says that with lots of sunlight and an abundance of food, filter-feeding animals like these would usually dominate, according to CTV News Canada.
"Somehow, some really specialized members of the filter-feeding community can survive," he said. "They could be brand-new species or they could just be an incredibly hardy version of what normally lives in Antarctica — we just don't know. My guess would be that they are potentially a new species."
Griffiths explained, "If they are living somewhere as tough as this, they are probably specially adapted to being there. There is a good chance they might go weeks, months, and years without food — you have to be pretty hardy to cope with that."
“This means that as polar scientists we are going to have to find new and innovative ways to study them and answer all the new questions we have.”
More about British Antarctic Survey, Sponges, antarctic ice shelf, extreme conditions, Sessile Benthic Community
 
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