Ice-covered Lake Enigma In Antarctica Supports Unique Microbial Communities

Northern Foothills of Victoria Land, Antarctica contains numerous hydrological formations, ranging from small surface streams and ponds fed by glacial or snow meltwater to permafrost lakes containing briny pockets.

Here we describe the discovery of a massive body of unfrozen stratified oligotrophic water in Lake Enigma, a permanently ice-covered lake previously thought to be frozen from top to bottom.

Northern Foothills of Victoria Land, Antarctica contains numerous hydrological formations, ranging from small surface streams and ponds fed by glacial or snow meltwater to permafrost lakes containing briny pockets. — Nature

A remarkable feature of the Lake Enigma microbial ecosystem is the presence, and sometimes even dominance, of ultrasmall bacteria belonging to the superphylum Patescibacteria, a group apparently absent from Antarctic lakes in the well-studied McMurdo Dry Valleys.

Cyanobacteria are virtually absent from Lake Enigma ice and water column although they are well represented in its extensive and diverse benthic microbial mats.

Collectively, these features reveal a new complexity in Antarctic lake food webs and demonstrate that in addition to phototrophic and simple chemotrophic metabolisms, both symbiotic and predatory lifestyles may exist.

Underwater survey of the bottom of Enigma Lake made at three different drilling points: A, B DP#2 (depth 9.3 m); C, D DP#4 (depth 22.5 m); E, F, DP#C22 (sampling depth 22.0 m). Evidence of supraglacial meltwater inflow from Amorphous Glacier to the surface of Lake Enigma evidenced during the XXXV Italian Antarctic Expedition on January 3, 2020 (G, H). — Nature

The perennially ice-covered Lake Enigma, Antarctica supports unique microbial communities, Nature (open access)

Astrobiology