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Accidental discovery deep under Antarctic’s ice could change what we know of life in the cold

Geologists discover strange lifeforms attached to a boulder under Antarctic ice shelf, more than 500 km from the nearest access points to nutrients and sunlight.

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Chennai: A team of geologists were drilling through Antarctic ice to collect sediment core samples from under an ice shelf, when their drill hit a boulder that had lifeforms attached to it.

The discovery by researchers from the British Antarctic Survey is the first-ever record of a hard substrate community or lifeforms that live in ecosystems involving stone, deep underneath an ice shelf. The findings were made underneath 900m of ice in the Filchner-Ronne Ice Shelf, situated on the South Eastern Weddell Sea.

The animals discovered here are stationary — some are sponges while others are unknown species — and they are attached to the boulder on the sea floor.

The findings were published in the Frontiers in Marine Science journal Monday.


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Extremophiles

The extremophiles found attached to the Antarctic boulder are both sponge-like as well as ‘stalked’ or having stalk-like filaments to which their bodies are attached.

Extremophiles are organisms that thrive in unlikely places under extreme conditions, such as environments with intense heat, extremely low oxygen, complete darkness, extreme pressures, and even the vacuum of space.

In biology, organisms that are immobile and attached to something stationary are considered to be “sessile”.

Sessile organisms on the ocean floor are believed to be restricted to places where there is abundant flow of incoming water carrying nutrients (‘inflow’), as they cannot move around for food. Such areas are typically found closer to the edge of the ice shelf and therefore it was believed that lifeforms are less in abundance with increased distance from open waters under the ice.

Previously, the farthest lifeforms from open waters that were observed under an ice shelf were found 700km from the Ross Ice Shelf front. Benthic or sea-floor organisms were observed moving around in this region but no living sessile organisms were observed.

The current findings were made at a depth of 1,233m and about 260km from the recent calving or edge where the ice shelf broke.

However, they were found in the direction opposite to the flow of water currents which could bring nutrients that could sustain these lifeforms.

In oceanic currents near the sea floor, nutrients flow from where photosynthesis occurs in the open ocean or where sunlight is present. The nearest two places that could potentially bring nutrient-carrying saltwater towards these organisms are at least 625 km and 1,500 km away.

Finding lifeforms under a floating ice shelf, in pitch darkness, in an area of outflow this far away from the open ocean is extremely rare. More studies are needed to understand how these creatures feed and multiply, noted the researchers.

The water temperature is approximately a standard -2 degree Celsius under the ice.

Mysterious life forms

The organisms, stuck to the sides of the boulder, are suspension feeders — organisms that feed on particles suspended in the waters.

Three types of such organisms were found: stalked sponge, non-stalked sponge and unidentifiable group of stalked creatures that are likely to be similar to carnivorous sponges.

The third group comprised 58 per cent of all observed organisms (22 in number), and the longest of them was approximately 6.6cm in length. There were 16 sponges.

The team drilled through the 890m thick ice shelf between 2015 and 2017 and used a GoPro HERO4 video camera housed in a pressure-protecting container.

It is still unclear how old these creatures are, how old their species are, how often they feed, and how abundant life is here. But the boulder is likely not an exception, the same video footage also captured a sponge on a nearby rock.

“This discovery is one of those fortunate accidents that pushes ideas in a different direction and shows us that Antarctic marine life is incredibly special and amazingly adapted to a frozen world,” said biogeographer and lead author, Dr Huw Griffiths of British Antarctic Survey, in a statement.


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