Scientists Discover a Whole New Ecosystem Teeming With Life in a Hidden Lake Beneath the Antarctic Ice

For decades, aerial images of Antarctica’s Northern Foothills depicted a frozen stillness blanketed by thick ice. Here and there, the white landscape featured hydrological formations like ice-lake blisters, saltwater bodies, briny pockets, and meltwater ponds. The largest of these formations was Lake Enigma. Little did researchers know that like its name, the lobate-shaped lake secretly hosted a treasure trove of enigma deep within its dark, icy belly. In the summer of 2019 and 2020, some researchers dropped a ground-penetrating radar and tiny cameras in the lake to extract samples of the icy water. Back in the laboratory, their jaws dropped open when they tested the samples. The study's findings are published in the journal Communications Earth and Environment.

Lake Enigma sits between two glaciers, Amorphous and Boulder Clay, whose average temperature oscillates between –40.7 degrees Celsius and -14 degrees Celsius. Given this scale of temperature, researchers were certain that the lake was packed with ice from top to bottom. It was believed that the lake froze somewhere around 14 million years ago, and ever since, the possibility of any ecosystem lurking inside the lake has been continuously discarded.

Lake Enigma derives its name from the thin veneer of ice-cored debris cones jutting upwards from its surface due to glacial drift. The unusual geochemistry of the lake is also attributed to the constant dipping of its ice due to its high precipitation, fierce katabatic winds, and intense solar evaporation. Yet the likelihood of any life in the lake was meager, if not impossible. But in a surprising twist, a team of polar researchers from the National Research Council of Italy stumbled upon a fledgling and thriving ecosystem with colonies of microbes and bacterial communities.

The team employed electric drills to send cameras down into the lake and announced that their equipment had sensed liquid water. “A massive body of unfrozen stratified oligotrophic water covered by up to 11 meters of ice was discovered and sampled,” they noted in the study and added that although the ice cover is estimated to be at least 12 meters deep, it could be even deeper. Extreme care was taken with the equipment so it didn’t end up contaminating the fascinating lifeforms breathing on the lake’s floor. The drills were sterilized and deeper layers were bored with heat melt and hot water drilling.

Underwater videos collected by the team revealed that the lake’s bottom was covered in thick microbial mats that resembled “crumpled thick carpets.” Protruding upwards from these mats were elongated cuspate pinnacles. Additionally, the cameras spotted a soft, creamy amorphous structure slathered with a superficial filamentous green-brown layer. Skulking within these mats was plenty of cyanobacteria, the primary reproducer of the entire ecosystem. "The ice-sealed planktonic and benthic microbiota of Lake Enigma likely represent persistent legacy biota that arose from the lake's ancient microbial ecosystem before the freeze-up," the team wrote.

This mysterious ecosystem hiding on the lake’s floor contained varieties of bacteria including Pseudomonadota, Actinobacteriota, and Bacteroidota, along with an unexpected bounty of Patescibacteria. These bacteria “have adopted an obligate symbiotic or predatory lifestyle, relying entirely on their respective prokaryotic host cells,” the researchers deduced. "The ultrasmall Patescibacteria in particular may play unusual roles in the lake's ecosystem that do not play out in other ice-covered Antarctic lakes.”

This discovery at Lake Enigma will continue to spark the curiosity and enigma of researchers studying the microbiology of Antarctica’s perennially ice-covered lakes. “Perennially ice-covered freshwater ecosystems are hotspots of biodiversity in Antarctica’s polar deserts, providing a year-round oasis for microbial life. This study describes a unique example of these ecosystems by adding the massive freshwater Lake Enigma, one of the deepest hydrological formations in Victoria Land,” they concluded.