What would you expect to find within a permanently frozen Antarctic lake? As if the name Lake Enigma wasn’t mysterious enough, polar scientists have just discovered unique microbial groups living their best lives beneath its icy surface.
An international team of polar researchers has discovered microbiota—a community of microorganisms—living beneath the permanently frozen ice cover of Antarctica’s Lake Enigma. Their findings, detailed in a December 3 study published in the journal Communications Earth & Environment, reveal a previously unknown ecosystem and hint at a lake once thriving with life before it froze over.
Lake Enigma sits between two glaciers, Amorphous and Boulder Clay, in Antarctica’s Northern Foothills. Given the area’s average temperature of 6.8 degrees Fahrenheit (-14 degrees Celsius) and lows of up to -41.26 degrees Fahrenheit (-40.7 degrees Celsius), experts understandably assumed that Lake Enigma was completely frozen.
During the summers of 2019 and 2020, the team—including researchers from the Institute of Polar Sciences, National Research Council of Italy (ISP-CNR)—discovered, to their surprise, that the lake was not fully frozen. Using ground-penetrating radars, they found a layer of water with a maximum depth of 39.4 feet (12 meters) about 36 feet (11 meters) below the icy surface.
Consequently, the team drilled through the ice to collect samples with a technique that prevented the water from getting contaminated. Back at the lab, the researchers found something surprising in the samples: life.
They identified microorganisms, including bacteria such as Pseudomonadota, Actinobacteriota, and Bacteroidota, and also the “presence, and sometimes even dominance, of ultrasmall bacteria belonging to the superphylum Patescibacteria,” the researchers wrote in the study. Superphylum Patescibacteria is an extremely simple bacteria with limited functions.
“Collectively, these features reveal a new complexity in Antarctic lake food webs,” the researchers wrote.
According to these results, the team suggests that the lake may have once hosted a thriving and diverse community of microorganisms before freezing over. Though it is unclear when Lake Enigma froze, the entire continent of Antarctica was covered in ice by about 14 million years ago, suggesting that Lake Enigma would have frozen by that time as well. Once the ice set in, some of the microorganisms must have survived, meaning that the bacteria the researchers identified in their labs might be the descendants of this original ancient community. After developing in isolation for perhaps millions of years, however, they are likely different from their ancestors.
Antarctica is classified as a desert; despite its thick ice sheets, it has very low precipitation. As a result, the researchers also suggested that, since the lake hasn’t dried out yet, it likely has an undiscovered source of water—probably the nearby Amorphous Glacier. However, Lake Enigma is still “isolated from the external environment by a permanent ice cover” and features a “chemically stratified water column,” according to the study. In other words, its isolation and stable stratification indicate that the glacier’s potential drainage hasn’t introduced any significant external contamination.
Ultimately, the discovery of microorganisms in such extreme environments sheds light on current Antarctic life forms invisible to the naked eye, and hints to the ancient ecosystems that thrived on the frozen continent millions of years ago.
Related article: Evidence of Life Found in Lake Deep Beneath Antarctic Ice
