A team of British scientists has discovered microbial life dwelling in one of the most inhospitable environments on Earth: the bottom of a lake trapped under miles of glacial ice in Antarctica.
Sampling such a setting has been possible only quite recently as ice sheets melt and recede at unprecedented rates due to increasing polar temperatures. Even so, some recent attempts have met with difficulties. A different British expedition at Lake Ellsworth in December 2012 suffered equipment failures and had to be cancelled.
However, the current British attempt has had much better fortune. This expedition is led by David Pearce of the University of Northumbria and consists of researchers from that institution, the University of Edinburgh, and the British Antarctic Survey (BAS). Pearce and colleagues used clean coring techniques to drill into sediments at the bottom of Lake Hodgson. This subglacial lake is on the Antarctic Peninsula and was entombed under more than 400 meters of ice at the end of the last Ice Age, but now has only a thin three to four-meter crust of ice. The lake is 93 meters deep and about 1.5 kilometers long by 1.5 kilometers wide.
The team drilled down through the ice, the water column, and into the sediment at the bottom of the lake. The topmost centimeters of the core produced current and recent organisms that inhabit the lake. However, three meters deeper down the core, fossil DNA was found that indicates types of microbes that date back 100,000 years to when the lake was first covered by the ice.
The genetic material in the core sample reveals that a very diverse microbial ecosystem exists in the sediment at the bottom of Lake Hodgson. One DNA sequence is related to the most ancient organisms known on Earth. In 23% of the genetic material, the researchers found DNA that has not been previously described, indicating the presence of many species new to science. These extremophiles are adapted to thrive in the most demanding environments, and employ an array of chemical processes to sustain themselves.
“What was surprising was the high biomass and diversity we found,” Pearce explained in a BAS press release. “This is the first time microbes have been identified living in the sediments of a subglacial Antarctic lake and indicates that life can exist and potentially thrive in environments we would consider too extreme.”
The findings in Lake Hodgson and other subglacial lakes could reveal how life can sustain itself in extreme settings, and perhaps on other worlds, such as Jupiter’s moon Europa, which is thought to house a global ocean of liquid water under a shell of ice.
The new discovery has been published online in a special issue of the journal ‘Diversity’ dealing with Microbial Ecology and Diversity.