Microbes, Fungi & Algae, Earth

Buried Antarctic lake teems with lifeMicrobes living in a lake deep under ice buoy the idea that life may inhabit otherworldly sites

By Thomas Sumner 8:30am, August 21, 2014

Brent C. Christner (right), of Lousiana State University, and Alex Michaud, of Montana State University, retrieve the first watersample from Antarctica's Lake Whillans.

Reed Scherer, Northern Illinois University

On Jan. 28, 2013, a team of U.S. scientists retrieved water from a liquid lake deep below thethick, West Antarctic Ice Sheet. Within hours, excited biologists reported they had found whatthey were looking for: live cells. But they refused to say more. Now, 19 months later, they’reready to talk.

“The number of microorganisms we saw in the water was very comparable with what you’d findin a typical surface lake or in the ocean,” notes Brent Christner. “We were very surprised.”

Christner works at Louisiana State University in Baton Rouge. Last year, this microbiologist ledthe team of biologists in Antarctica that initially analyzed water from Lake Whillans. Christneralso led the scientific team that now describes those microbes in the Aug. 21 Nature.

The U.S. research team had used hot water to carefully tunnel 800 meters (roughly a half-mile)down through ice until it breached the surface of Lake Whillans. Then they hoisted 30 liters (8gallons) of the lake’s water to the surface. In it, they found a surprising abundance of bacteria

This image taken with a scanning electron microscopeshows a ball-shaped microbe recovered from LakeWhillans. The lake’s large and diverse microbialpopulation surprised scientists.Trista Vick-Majors

and other one-celled organisms called archaea. Each thimbleful of water contained roughly130,000 cells. In all, the biologists found 3,931 microbial species or groups of species.

All had been living in the lake’s pitch-black water.Its temperature was a frigid 0.49° Celsius (31.1°Fahrenheit) at the time of sampling. By looking atthe isotope of oxygen that dominated in the water,they could see that it matched that of the glacier iceabove. That indicated the lake’s water had meltedoff the bottom of the glacial ice sheet. Indeed, thethick glacial ice serves like a blanket to insulate thelake from temperatures at the surface, whichremain below freezing year-round.

Keeping the lake clean

For decades scientists had known that a network ofrivers and more than 400 subglacial lakescrisscross the bottom of Antarctica’s 14-millionsquare kilometer (5.4-million square mile) icecover. Geothermal warmth is responsible for turning the base of some of the glacial ice into thisliquid water.

Five years ago, researchers reported finding life in cores of ice collected above Vostok, asubglacial lake much deeper than Whillans. Critics, back then, had argued that the few cellsrecovered above Lake Vostok might simply be due to contamination. The drilling equipmentmight have brought down surface germs. Since then research teams from Russia, the UnitedKingdom and the United States have each launched drilling efforts to search for proof of lifetucked away under the Antarctic ice.

For its work at Lake Whillans, the U.S. research team created a new type of hot-water drill. Itheats up filtered water. That water then melts a hole down through the ice.

That drill water gets so hot that it should kill any microbes trying to hitchhike down from thesurface. The drill system further disinfects the water with hydrogen peroxide. Lastly, the water iszapped with intense ultraviolet light to kill off any remaining germs.

Each minute that the drill operated, it pumped more than 113 liters of water — enough to fill atypical bathtub. That water traveled down what Christner describes as a kilometer-long industrialgarden hose. Along the way, that water melted a cylindrical hole 60 centimeters (23.6 inches)wide.

These precautions weren’t just to get a clean, scientific result. Explains Christner, “The lastlegacy that we’d want to leave is messing up the lake with foreign material that might alter it.”

Even the lake itself was selected to minimize environmental problems, Christner says. Vostok’swater has likely been in that lake for more than 10,000 years. By contrast, the water in LakeWhillans flushes out every few years. By choosing to work with a relatively quick-flushing lake,the U.S. team figured it would cut any chance of long-term contamination if there had been adrilling mishap.

Bacteria colonies from several different species thatwere collected from Lake Whillans. They are seengrowing in the lab in a dish. The abundance and varietyof lake microbes surprised scientists.Brent Christner

A water sample brimming with life. Scientists hauled itup in early 2013 from a lake buried 800 meters (a halfmile) below the Antarctic ice sheet. The brownish colorcomes from tiny silt particles in the water.Trista Vick-Majors

A window into life on other worlds?

Unlike microbes living on Earth’s surface, LakeWhillans’ inhabitants live a pitch-black existence.Without sunlight for photosynthesis, many of theorganisms instead eat away at the surroundingrock and produce energy by oxidizing iron.(Oxidation is a chemical reaction that involves onemolecule’s theft of an electron from another.)

Christner suggests that the vibrant ecosystem fueled by these rock-chomping microbes supportsthe possibility of life elsewhere in the solar system. Such as where? Perhaps at Mars’ polaricecaps or on Jupiter’s moon Europa, he says.

“If you took one of these microbes and put it under an ice sheet where there’s water on anotherplanet, I don’t think [the microbes] could tell the difference,” Christner says.

Martyn Tranter is a biogeochemist at the University of Bristol in England. “It’s not too much of astretch of the imagination,” he says, to now think “that ice sheet beds on other planets andterrestrial bodies can be hosts to microbial life.” Having definitive proof of life under the Antarcticice sheet also provides insight into how life might cope with something as devastating as a globalnuclear war, he argues. Afterward, there would likely develop what physicists refer to as a “anuclear winter or snowball Earth.” Yet even under such extreme conditions, he says, “thesemicrobes would still carry on.”

Power Words

Antarctica A continent mostly covered in ice, which sits in the southernmost part of the world.

archaeon (plural archaea) A domain of life that includes single-celled organisms. Althougharchaea superficially resemble bacteria, they are distinct. Archaea inhabit many harsh

environments.

bacterium (pluralbacteria) A single-celled organism forming one of the three domains of life.These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.

biogeochemistry A term that covers processes that cycle (or eventually deposit) pure elementsor chemical compounds (including minerals) between living species and nonliving parts (such asrock or soil or water) within an ecosystem. A scientist who works in this field is abiogeochemist.

ecosystem A group of interacting living organisms — including microorganisms, plants andanimals — and their physical environment within a particular climate. Examples include tropicalreefs, rainforests, alpine meadows and polar tundra.

Europa The fourth largest moon of Jupiter. Europa, 1,951 miles across, has a network of darklines on a bright, icy surface.

glacier A slow-moving river of ice hundreds or thousands of meters deep. Glaciers are found inmountain valleys and also form parts of ice sheets.

hydrogen peroxide A molecule made of two hydrogen and two oxygen atoms. Highly reactive,it can kill many tiny organisms, including germs.

ice sheet The broad blanket of ice, most of it kilometers deep, that covers most of Antarctica.An ice sheet also blankets most of Greenland.

isotopes Different forms of an element that vary somewhat in weight (and potentially inlifetime). All have the same number of protons but different numbersneutrons in their nucleus. Asa result, they also differ in mass.

microbe Short for microorganism. (see microorganism)

microorganism A living thing that is too small to see with the unaided eye, including bacteria,some fungi and many other organisms such as amoebas. Most consist of a single cell.

oxidation A process that involves one molecule’s theft of an electron from another. The victimof that reaction is said to have been “reduced.” It can make itself whole again by robbing anelectron from another molecule, triggering another case of oxidation. These chemical reactionsare so violent, chemically, that they can easily kill cells. The oxidative reaction often involvedoxygen atoms — but not always.

photosynthesis (verb: photosynthesize)The process by which green plants and some otherorganisms use sunlight to produce foods from carbon dioxide and water.

terrestrial An adjective for things of or relating to Earth

ultraviolet A portion of the light spectrum that is close to violet but invisible to the human eye.

D. Fox. “Mystery microbes of the sea.” Science News for Students. Sept. 26, 2013.

Further Reading

D. Fox. “Mud worth more than gold.” Science News for Students. Sept. 4, 2013.

D. Fox. “Explainer: Antarctica, land of lakes.” Science News for Students. Sept. 4, 2013.

D. Fox. “Explainer: Ice sheets and glaciers.” Science News for Students. Sept. 4, 2013.

D. Fox. “Animals under Antarctic ice?” Science News for Students. July 22, 2013.

J. Raloff. Life found deep below Antarctic ice. Science News. Vol. 183, March 9, 2013, p. 12.

J. Raloff. “Piercing a buried polar lake.” Science News for Students. Jan. 29, 2013.

J. Raloff. U.S. team breaks through subglacial lake. Science News Online, January 28, 2013.

J. Raloff. “Antarctic test of novel ice drill poised to begin.” Science News blog. Dec. 15, 2012.

P. Rejcek. “WISSARD project poised to explore subglacial Lake Whillans.” The Antarctic Sun.Nov. 9, 2012.

Original Journal Article: B. Christner et al. A microbial ecosystem beneath the West Antarcticice sheet. Nature. Vol. 512, August 21, 2014, p. 310. doi: 10.1038/nature13667.

Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) home page.

Source URL: https://student.societyforscience.org/article/buried-antarctic-lake-teems-life