What would you expect to find inside a permanently frozen Antarctic lake? As if Enigma Lake’s name wasn’t mysterious enough, polar scientists have just discovered unique microbial groups that live their best lives beneath its icy surface.
An international team of polar researchers has discovered the microbiota, a community of microorganisms, living beneath the permanently frozen ice sheet of Antarctica’s Enigma Lake. Their findings, detailed in a December 3 study published in the journal Earth and Environment Communicationsthey reveal a previously unknown ecosystem and hint that a lake thrived with life before it froze.
Enigma Lake is located between two glaciers, Amorphe and Boulder Clay, in the northern foothills of Antarctica. Given the area’s average temperature of 6.8 degrees Fahrenheit (-14 degrees Celsius) and lows as low as -41.26 degrees Fahrenheit (-40.7 degrees Celsius), experts understandably assumed that Enigma Lake he was completely frozen.
During the summers of 2019 and 2020, the team—including researchers from the Institute of Polar Sciences, Italian National Research Council (ISP-CNR)—discovered, to their surprise, that the lake was not completely frozen . Using ground-penetrating radar, they found a layer of water with a maximum depth of 39.4 feet (12 meters) about 36 feet (11 meters) below the frozen surface.
Consequently, the team drilled through the ice to collect samples using a technique that prevented the water from becoming contaminated. Back in the lab, the researchers found something surprising in the samples: life.
They identified microorganisms, including bacteria such as Pseudomonadota, Actinobacteriotai Bacteroidotaand 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 bacterium with limited functions.
“Collectively, these features reveal new complexity in Antarctic lake food webs,” the researchers wrote.
Based on these results, the team suggests that the lake may have once hosted a thriving and diverse community of microorganisms before it froze. Although it is not clear when Enigma Lake froze, the entire continent of Antarctica was covered in ice for about 14 million years agosuggesting that Enigma Lake would also have frozen over at that time. Once the ice settled, some of the microorganisms must have survived, meaning that the bacteria the researchers identified in their labs could be the descendants of that ancient original community. However, after developing in isolation for perhaps millions of years, they are likely to be different from their ancestors.
Antarctica is classified as a desert; despite its thick layers of ice, it has very little precipitation. As a result, the researchers also suggested that since the lake has not yet dried up, it likely has an undiscovered water source, most likely the nearby amorphous glacier. However, Enigma Lake is still “isolated from the external environment by a permanent ice cover” and exhibits a “chemically stratified water column,” according to the study. In other words, its isolation and stable stratification indicate that the Potential glacier drainage has not introduced any significant external pollution.
Ultimately, the discovery of microorganisms in such extreme environments sheds light on present-day Antarctic life forms invisible to the naked eye and hints at the ancient ecosystems that thrived on the frozen continent millions of years ago.
Related article: Evidence of life found in lake under Antarctic ice
