Researchers Find Ancient Microbes in Ice-Sealed Antarctic Lake

Scientists led by Prof Peter Doran of the University of Illinois at Chicago have discovered a 3,000-year-old viable community of bacteria in a dark, salty and subfreezing environment beneath about 65 feet (20 meters) of ice in Lake Vida, one of Antarctica’s most isolated lakes.

This scanning electron micrograph shows bacterial cells that inhabit icy brine channels in Antarctica’s Lake Vida, which lies in the Victoria Valley, one of the northernmost of the Antarctic dry valleys (Christian H. Fritsen / Desert Research Institute)

Life in Lake Vida lacks sunlight and oxygen. The lake is mostly frozen and possesses the highest nitrous oxide levels of any natural water body on Earth. A briny liquid that is approximately six times saltier than seawater percolates throughout the icy environment that has an average temperature of minus 13.5 degrees C (or 8 degrees F).

Dr Alison Murray of Nevada’s Desert Research Institute, lead author of the study reporting the discovery in the Proceedings of the National Academy of Science, said: “this study provides a window into one of the most unique ecosystems on Earth. Our knowledge of geochemical and microbial processes in lightless icy environments, especially at subzero temperatures, has been mostly unknown up until now. This work expands our understanding of the types of life that can survive in these isolated, cryoecosystems and how different strategies may be used to exist in such challenging environments.”

The researchers drilled out cores of ice, using sanitary procedures and equipment, and collected samples of brine within the ice and assessed its chemical qualities and potential for sustaining life. They found that the brine is oxygen-free, slightly acidic, and contains high levels of organic carbon, molecular hydrogen, and both oxidized and reduced compounds.

Despite the very cold, dark and isolated nature of the habitat, they also found that the brine harbors a surprisingly diverse and abundant assemblage of bacteria that survive without a present-day source of energy from the Sun. Previous studies of the lake dating back to 1996 indicate that the brine and its’ inhabitants have been isolated from outside influences for more than 3,000 years.

“This provides us with new boundary conditions on the limits for life,” Prof Doran said. “The low temperature or high salinity on their own are limiting, but combined with an absence of solar energy or any new inputs from the atmosphere, they make this a very tough place to make a living.”

Research field camp on Lake Vida, located in Victoria Valley, the northern most of the McMurdo Dry Valleys (Alison Murray / Desert Research Institute)

“Geochemical analyses suggest that chemical reactions between the brine and the underlying sediment generate nitrous oxide and molecular hydrogen,” said Prof Fabien Kenig of the University of Illinois at Chicago. “The hydrogen may provide some of the energy needed to support microbes.”

“We’d like to go back and find if there is a proper body of brine without ice down there,” Prof Doran said. “We’d also like to get some sediment cores from below that to better establish the history of the lake. In the meantime, we are using radar and other geophysical techniques to probe what lies beneath.”

_______

Bibliographic information: Alison E. Murray et al. Microbial life at −13 °C in the brine of an ice-sealed Antarctic lake. PNAS, published online before print November 26, 2012; doi: 10.1073/pnas.1208607109