Antarctica is one of the most extreme environments on Earth. It is also one of the most unexplored.
Many of us think of the continent as a vast white desert, populated by nothing more than penguins and seals. But beneath its icy surface, scientists are beginning to uncover vast webs of complex lifeforms that have not been seen anywhere else on the planet.
There are two types of Antarctic ice: land ice and sea ice. Pack ice forms when the upper layers of the Southern Ocean freeze. Ice cover is seasonal, and in the summer most of this ocean ice melts.
Blooms of photosynthetic algae have been observed in these regions as soon as the ice melts. But until recently, it was often assumed that the packed pack ice prevented any light from reaching the lower layers before this seasonal transition.
However, new research suggests that blooms of photosynthetic algae, called phytoplankton, can grow and even thrive before the ice retreats.
Phytoplankton form the basis of most aquatic food webs and support the growth of other complex life forms. Using data collected by NASA’s Earth-monitoring satellites and on-site ocean floats, researchers from Brown University and the University of Auckland have found evidence of large areas of these lifeforms. photosynthetic living under the frozen surface.
“The discovery of these blooms helps challenge the paradigm that regions under sea ice are lifeless, and introduces important new questions about the food webs that may lie under the ice in Antarctica,” he said. Christopher Horvat, who led the study, published in the journal. Frontiers of Marine ScienceTold Newsweek.
“We think they could cover up to 5 million square kilometers of the region under the Southern Ocean ice.”
The pack ice of the Southern Ocean is composed of discrete sheets of packed ice. Between these leaves, small areas of open water allow light to pass through, allowing photosynthesis.
Huw Griffiths, a marine biogeographer with the British Antarctic Survey, explained that sea ice itself is usually only about three to ten feet thick and therefore also allows light to reach surface waters directly. below.
However, life has also been discovered in areas that never saw the light of day. “Most ice shelves are so thick that no light reaches the seabed below,” Griffiths said. Newsweek.
Ice shelves are made primarily of the second type of Antarctic ice: land ice. They form when huge slabs of ice are pushed from the land to the surface of the ocean. Unlike sea ice, these slabs can reach thousands of feet deep.
In 2021, Griffiths and his team discovered marine life forms on a rock at the bottom of the sea under an Antarctic ice floe, 3,000 feet below the surface.
“We know very little about life under the floating ice shelves of Antarctica. The ice shelves cover about a third of the continental shelf – 1.5 million square kilometers – but our knowledge is based on a handful of borehole records drilled through the ice shelves,” he said. .
“These holes give us small snapshots of what lives on the seafloor and the water column, but the majority of what we know comes from short video clips and photographs covering a very small area.
“Current theories of what life might survive under the ice shelves suggest that all life becomes less abundant the further you get from open water and sunlight,” he continued. .
“Previous studies have found small mobile scavengers and predators, such as fish, worms, jellyfish or krill, in these habitats. probable filter-feeding animals such as sponges.”
Moving inland, the frozen wastelands of Antarctica hide a hidden realm of hundreds of subglacial lakes and rivers, teaming with life. In 2014, Lake Whillans, the continent’s third-largest lake, which sits 2,600 feet below the West Antarctic Ice Sheet, was shown to contain nearly 4,000 different microbial species.
In June, researchers in New Zealand recorded swarms of shrimp-like creatures in an underground river beneath the Ross Ice Shelf at the southern tip of the continent.
Taken together, these findings indicate just how diverse the different life forms are under the ice of Antarctica.
“Animals that survive deep below ice shelves must be adapted to extreme cold, with water temperatures as low as -2.2 degrees Celsius (28 degrees Fahrenheit),” Griffiths said. “They should also be adapted to low amounts of food, similar to deep-sea creatures. These organisms live hundreds of miles from the nearest daylight and sources of fresh phytoplankton.”
Such adaptations open up the possibility that similar ecosystems may exist in other frozen landscapes.
“The discovery of complex animal life – over [just] microbes – under such extreme conditions, suggests that complex life could possibly survive beyond Earth on frozen moons, such as Jupiter’s Europa, Ganymede and Callisto, and planets, where liquid water flows beneath the icy surface,” Griffiths said.
But these studies also tell us about life on our own planet.
“Antarctica is one of the most extreme environments on Earth,” Griffiths said. “We have names for almost ten thousand species, but on each visit we find that between 10 and 20% of the species we find are new to science. There could be up to ten thousand more species to discover. !
“Working in Antarctica is never boring, always challenging and always surprising. It also requires enormous international cooperation – no single country could study this huge frozen continent alone,” he said.
As human influence extends to every corner of the planet, Antarctica’s intact ecosystems are under threat. Due to global warming, the Antarctic ice sheets are melting at a rate of around 150 billion tonnes per year, with devastating consequences for sea levels worldwide.
“Antarctica faces many challenges in its future, with climate change and human impacts already altering the habitats we find there,” Griffiths said. “Packets and sea ice are already changing, and seawater is getting warmer and more acidic. We have found microplastics in water, sediments and animals, and other pollutants from industrialized countries have found their way into the Southern Ocean.
“Most people don’t know much more about Antarctica’s unique wildlife and biodiversity than the penguins and seals that live on the surface. But over 90% of Antarctic species are found on the seafloor and more than half of them are found nowhere else on Earth.
“This makes Antarctica a special and globally significant biodiversity hotspot and a place that needs our help to stay healthy and able to support such an abundance of life.”
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Horvat C, et al., Evidence For Phytoplankton Blooms Under Antarctic Sea Ice, Front. Mars Sci., 17 Nov 2022, doi: 10.3389/fmars.2022.942799
Griffiths HJ, et al., Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Under an Antarctic Ice Shelf, Front. Mars Science. February 15, 2021, https://doi.org/10.3389/fmars.2021.642040
Christner, B., Priscu, J., Achberger, A. et al., A Microbial Ecosystem Beneath the West Antarctic Ice Sheet, Nature, 20 Aug 2014, https://doi.org/10.1038/nature13667
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