By Colin Barras
During the last decade, researchers began drilling into Antarctica’s ice-covered lakes in search of life. Now we have what may be the clearest evidence yet of biologically complex life in one of these lakes – although it’s not yet clear whether any of the animals are currently alive.
According to a report in Nature, a few weeks ago a team of US biologists discovered the preserved carcasses of tiny crustaceans and tardigrades in the mud at the bottom of Lake Mercer, which lies beneath a kilometre of ice.
The discovery raises two questions: how did the animals get there, and are there any still living in the lake today?
According to the report, animal ecologist Byron Adams at Brigham Young University in Utah has had a chance to examine the dead animals and other organic remains in the mud. He has noticed similarities to communities that once lived in the Dry Valleys, a few hundreds of kilometres from Lake Mercer, and also in the Transantarctic Mountains a few tens of kilometres from the lake.
He suspects the animals lived in rivers or lakes in the mountains when the climate was briefly warmer, perhaps just a few thousand years ago. From there, the animal carcasses were somehow washed into Lake Mercer – perhaps, according to other researchers, in rivers that run beneath the ice.
This would suggest that Lake Mercer is simply an animal graveyard rather than a body of water with living animal communities. That might make sense. Lake Mercer is buried beneath a layer of ice so thick that no light can reach the water. The microbes living there may grow too slowly to support communities of animals, Nature reports.
But Adams has apparently not given up hope of finding signs of living animals in the lake in future. And even if the animals in Lake Mercer are all dead, that might not be the end of the story.
Biologists have previously discovered that crustacean eggs buried in the mud at the bottom of lakes for centuries can hatch and grow – leading to a new branch of biology called “resurrection ecology”. If the tiny animals in Lake Mercer are just a few thousand years old, perhaps the mud at the bottom of the lake may contain viable eggs.
Investigations of other Antarctic lakes have found less complex microbial life. In 2014, one team discovered a thriving community of single-celled organisms in Lake Whillans, apparently surviving by eating the organic remains of ancient forests that once grew in Antarctica. Lake Vostok also seems to play host to life, and there are even intriguing hints that complex animals might survive there.
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