Located between the Amorphous and Boulder Clay glaciers in Antarctica is Lake Enigma, a body of water that regularly experiences temperatures around seven degrees Fahrenheit. During the winter, it can drop to -41 degrees.
For a long time, experts believed that the remote lake was completely frozen and unsuitable for life, as it formed during a warmer climate. However, new evidence indicates that some microbiotic life can survive in these inhospitable conditions.
The National Research Council of Italy's Institute of Polar Sciences led a team of researchers during the "XXXV Italian Expedition to Antarctica," which took place between November 2019 and January 2020. They utilized ground-penetrating radar to detect the presence of liquid water deep beneath the lake's frozen surface.
The water was found below ice caps ranging from about 11 to 36 feet deep, with a depth of at least 39 feet. The researchers employed a custom-made thermal melt head drilling system to obtain water samples without contamination, which were later analyzed in the laboratory.
The lab tests confirmed a total of 21 bacterial and eukaryotic phyla in the surface ice of Lake Enigma, along with layers of stratified water columns and microbial mats. Examples of the microbiota discovered include Pseudomonadota, Actinobacteriota, and Bacteroidota.
The most surprising discovery was of Patescibacteria, which are characterized by a small genome and minimal metabolic functions. These bacteria have adopted a symbiotic or predatory lifestyle, relying on prokaryotic host cells.
The research team theorized that the lake was once filled with living organisms before a permanent freeze occurred around 14 million years ago. Today's species are likely descendants of those from an ancient ecosystem.
The researchers concluded that the ice-sealed microbiota of Lake Enigma represent a persistent legacy of its ancient microbial ecosystem. They occupy different trophic levels within a simple aquatic food web, contributing to the lake's unique ecological dynamics.
Despite expectations that the lake would have dried up long ago, its continued existence suggests an unknown water source remains.