Antarctica’s Enigma Lake, located between the Amorphous and Boulder Clay Glaciers, regularly experiences temperatures around 7 degrees Fahrenheit. In the winter months, that number can drop to -41 degrees. Experts have long believed that the remote lake is completely frozen and inhospitable to life, but new evidence proves that at least some microbiotic life can find a way even in such frigid conditions.
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Researchers led by the National Research Council of the Italian Institute of Polar Sciences identified the single-celled organisms during the ‘XXXV Italian Antarctic Expedition’ that took place from November 2019 to January 2020. Despite their assumption that the lake was frozen and devoid of organisms, Pervasive Radar scans indicated the presence of liquid water beneath ice sheets about 3 to 10 meters deep. Beneath these icy blocks were layers of layered water columns at least 11 meters deep. Intrigued by the discovery, researchers then used a custom-made thermal melthead drilling system that allowed them to extract water samples without contaminating them.
Underwater surveys of the Enigma Lake bottom conducted at four different drill points. Credit: Communications Earth and Environment
According to the team’s paper, published December 3 in Communication Earth & Environmentsubsequent laboratory testing confirmed a total of 21 bacterial and eukaryotic phyla in Lake Enigma’s surface ice, stratified water column layers, and microbial mats. Examples included Pseudomonadota, Actinobacteriota and Bacteroidota, but as the study announcement explains, the most surprising finding was a “proliferation of the bacterial superphylum Patescibacteria.” These extremely simple life forms have a small genome, which means that their relatively small cells can only carry out a select number of processes with limited metabolic functions.
“As a result, these bacteria have adopted an obligate symbiotic or predatory lifestyle, being completely dependent on their respective prokaryotic host cells,” the study authors wrote.
Although more research is needed, the team theorizes that an ancient Enigma Lake may have once harbored a very different ecosystem, filled with a wide variety of living organisms. However, at some point in the past the body of water formed a permanently frozen top layer that exists to this day.
[Related: What will Antarctica look like in 2070?]
“The ice-covered planktonic and benthic microbiota of Lake Enigma likely represent persistent legacy biota that emerged from the ancient lake microbial ecosystem before the lake freeze,” researchers concluded. Because of this, the current ecosystem includes a “simple aquatic food web,” although some of the remaining microbacteria “may play unusual roles in the lake ecosystem, not found in other ice-covered Antarctic lakes.”
