A study by polar researchers has revealed an ancient community of bacteria able to thrive in the lightless, oxygen-depleted, salty environment beneath nearly 70 feet (20 metres) of ice in an Antarctic lake, giving insight into the unique ecosystem.
The research, funded by the National Science Foundation and NASA, provides clues about biochemical processes not linked to sunlight, carbon dioxide and oxygen – or photosynthesis.
The study, published this week in Proceedings of the National Academy of Science, came out of a collaborative effort of polar researchers from a number of institutions, including the University of Illinois at Chicago, Montana State University and the University of Colorado.
The energy driving bacterial life in Lake Vida, a mostly frozen, brine lake below the Antarctic ice shield, may be derived from chemical reactions between the salt water and the underlying, iron-rich rock, researchers said.
Conditions at Lake Vida are similar to habitats on Mars and are believed to be present elsewhere in the solar system, creating a potentially new framework for evaluating the likelihood of extraterrestrial life and how it might be sustained.
“It can tell us about the origins of life on Earth and it also educates us about looking for life elsewhere,” said Peter Doran, principal investigator with the Lake Vida project and environmental sciences professor at the University of Illinois at Chicago.
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The microbes in the isolated lake contain representatives from eight major bacterial groups, suggesting a complex ecosystem instead of a remnant population of a single life form, the research shows.
“It’s a dual-edged sword: We don’t want to sensationalize the findings but, at the same time, it’s very exciting,” Fritsen said.
The paper in question is "Microbial life at −13 °C in the brine of an ice-sealed Antarctic lake". The abstract is below.
The permanent ice cover of Lake Vida (Antarctica) encapsulates an extreme cryogenic brine ecosystem (−13 °C; salinity, 200). This aphotic ecosystem is anoxic and consists of a slightly acidic (pH 6.2) sodium chloride-dominated brine. Expeditions in 2005 and 2010 were conducted to investigate the biogeochemistry of Lake Vida’s brine system. A phylogenetically diverse and metabolically active Bacteria dominated microbial assemblage was observed in the brine. These bacteria live under very high levels of reduced metals, ammonia, molecular hydrogen (H2), and dissolved organic carbon, as well as high concentrations of oxidized species of nitrogen (i.e., supersaturated nitrous oxide and ∼1 mmol⋅L−1 nitrate) and sulfur (as sulfate). The existence of this system, with active biota, and a suite of reduced as well as oxidized compounds, is unusual given the millennial scale of its isolation from external sources of energy. The geochemistry of the brine suggests that abiotic brine-rock reactions may occur in this system and that the rich sources of dissolved electron acceptors prevent sulfate reduction and methanogenesis from being energetically favorable. The discovery of this ecosystem and the in situ biotic and abiotic processes occurring at low temperature provides a tractable system to study habitability of isolated terrestrial cryoenvironments (e.g., permafrost cryopegs and subglacial ecosystems), and is a potential analog for habitats on other icy worlds where water-rock reactions may cooccur with saline deposits and subsurface oceans.