It was a dark and cold ...
Scientists seek extremophiles in Antarctica's harshest environments
Posted October 26, 2012
It’s cliché but true: Antarctica represents the harshest environment on the planet.
That offers a hint about the nature of the research under way by Hubert Staudigel and colleagues, who head to some of the continent’s most gnarly environments to study how life ekes out a living, from the seafloor shadowed by sea ice to pitch-black caves atop an active volcano.
“The idea was to go to extreme environments around McMurdo Station . Many of them have no organic matter around — these are the ones where we would expect conditions like early Earth,” explained Staudigel, a research geologist at Scripps Institution of Oceanography at the University of California in San Diego . He is the lead principal investigator on a five-year project to learn how microbes live in nutrient-poor volcanic environments.
The project, which includes co-principal investigators Bradley Tebo at Oregon Health and Science University and Laurie Connell at the University of Maine , involves setting out experiments made of various forms of volcanic glass such as basalt. Minerals like phosphorous, iron or manganese are then added to the substrate.
“Things that microbes would like,” Staudigel explained. “The idea is to see if the microbes prefer a particular substrate.”
The early geological history of Earth was one of violent volcanism, among other processes. Primitive life may have been evolving during this phase of the planet’s eruptive past. Staudigel said there is evidence that early microbes may have left traces in volcanic glass that was formed from cooled molten lava by excavating hair-sized tunnels, possibly using inorganic materials for metabolic activity.
He and his team have been attempting to mimic those conditions in various locations around McMurdo Station, the largest research facility of the U.S. Antarctic Program . This is the fifth and final year of the field portion of the project.
The researchers have placed experiments in the highly stratified Lake Fryxell in the McMurdo Dry Valleys . The ice-covered lake is something like a layered cake, with high levels of oxygen near the top and rapidly decreasing toward the bottom from oxidation of organic materials that accumulate at the bottom. A mooring holds experiments throughout the water column to see how microbial communities differ between layers.
Other project sites include glacial rivers that go through volcanic rock in the McMurdo Dry Valleys. An altogether different location is under the sea ice in McMurdo Sound near Cape Evans, a site picked for comparison to microbes found deep on the seafloor near underwater volcanoes in the Pacific Ocean.
“This seafloor site allows us to make the link between our results from the deep oceans and Antarctica,” Staudigel said.
Finally, the researchers are collecting data atop Mount Erebus , an active volcano nearly 3,800 meters tall, where dark, nutrient-poor ice caves offer yet another variation on the extreme conditions of the planet, as it may have existed several billion years ago. Experiments have also been set at a site on Erebus called Tramway Ridge , where the warmest soils on the volcano are found.
“It’s a huge, huge undertaking in terms of samples we need to process,” Staudigel conceded.
But the study of such chemolithotrophs — organisms that grow without organic compounds or light — could prove to be a huge boon to understanding primitive life.
“The carbon fixation seems to be at a very basic level there,” Staudigel said. “It’s a very promising study.”
Photo Credit: Hubert Staudigel
An ice tower on Mount Erebus where gas vents from the flanks of the volcano.
So promising, in fact, that Staudigel’s team has plans for a follow-on project that will begin in the 2013-14 season focusing on the Mount Erebus ice caves, which are networks of passages melted into the base of the snowpack, where geothermal heat and warm gases vent through fissures in the flanks of the volcano.
The caves represent the ideal dark oligotrophic volcanic environment (DOVE), according to Staudigel. Such DOVE locations are generally difficult to find or access, such as the deep sea vents at the seafloor. The relative ease of accessing several of the 120 known caves makes them attractive for study, though reaching the dark recesses will require some mountaineering maneuvers with ropes.
Ensuring minimal contamination will also be important. Discussions are under way now to establish a permanent code of conduct to protect the unique geological and biological values represented by the ice caves. [See related story — Clean conduct: New rules proposed for entering ice caves on Mount Erebus.]
“[The caves] take on a very special role,” Staudigel said. “They are extremely starved in terms of organic matter. They’re dark, so basically there’s no carbon fixation by photosynthesis.”
But such dark places may illuminate the distant past.
NSF-funded research in this story: Hubert Staudigel, University of California-San Diego Scripps Inst of Oceanography, Award No. 0739712 ; Bradley Tebo, Oregon Health and Science University, Award No. 0739731 ; and Laurie Connell, University of Maine, Award No. 0739696 .