By Whitney Heins
Weeks of living in a tent tethered to a sheet of ice where the temperature never rises above freezing might not sound super appealing, but it’s something Jill Mikucki accepts as part of her job.
As a member of the National Science Foundation’s Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project team, she is one of roughly forty scientists investigating a complex network of lakes that lie beneath hundreds of meters of ice in Antarctica.
Mikucki, an assistant professor of microbiology at UT, and her team made science history in 2013 by punching through the West Antarctic Ice Sheet with a custom hot-water drill and retrieving the first evidence of microbial life from Subglacial Lake Whillans.
Interestingly, the lake is only about two meters deep but spreads out for twenty square miles. Trapped beneath a glacier, its water hasn’t come into contact with the atmosphere for possibly thousands of years—making it one of the most isolated bodies of water on the planet.
Clean Drilling
Scientists had tried but failed to obtain samples from subglacial lakes in the past. It took six years of planning to overcome fears that samples—and the lake—could be contaminated through the introduction of invasive organisms.
To prevent tainting the environment, a special drill fitted with filtration and germicidal systems was designed to recover pristine samples for microbial analysis. The numerous customized scientific samplers and instruments were also carefully cleansed before being lowered into the borehole.
It took days of around-the-clock drilling to gather about thirty liters of lake water and sediment core samples, enough to shed some light on what life under the ice looks like.
The samples were then preserved chemically or frozen and taken back to labs at UT and other partner institutions. Some, however, were analyzed in the field—another scientific first.
“Getting this real-time data was so important because once these microbes are taken out of their environment, their activity begins to change,” explained Mikucki. “One of the big unknowns is what the microbes are doing and how their activities might be affecting other ecosystems.”
Extreme Living
The data revealed a thriving ecosystem—about 130,000 cells per milliliter of lake water. The researchers used DNA-sensitive dye to determine whether the cells were present, and then examined their metabolic activity using radiotracers to determine if they were alive. DNA sequencing uncovered close to 4,000 different species—all single-celled bacteria and archaea.
“I wasn’t surprised to find life under the ice sheet, but I was surprised to find so much of it,” Mikucki said. She believes these organisms have been growing and changing to overcome challenges like living without sunlight for thousands of years.
Mikucki and her lab group employed genetic analysis to expose the organisms’ ability to generate energy by oxidizing sulphur found in the sediment. Collaborators also discovered evidence of iron and ammonium oxidation activities, likely left over from a time before the area was covered with glaciers.
The findings provide clues to life’s ability to persist in cold and dark isolation for extended periods of time. “I hope our findings motivate new research on the role of these extreme microorganisms in the function of our planet and other icy worlds in our solar system,” Mikucki said.
It’s All Connected
Because Subglacial Lake Whillans is linked to a major network of reservoirs, the researchers believe similar microbes may be thriving elsewhere. By altering minerals in sediments and supplying nutrients to ocean waters, these tiny organisms may be playing a role in the chemical and biological composition of the Southern Ocean—or even the entire planet.
As Antarctica’s ice shelf melts, “these microbes could be releasing nutrients into the ocean, affecting base-level chemistry—which affects larger organisms like fish and all the way up the food chain,” Mikucki explained.
To investigate further, the team recently fired up their drill in another area, known as the Grounding Zone, where the liquid waters of Subglacial Lake Whillans are thought to drain into the Ross Sea.
The data collected here mostly focused on the mechanics of the ice sheet, how it interacts with sediment and ocean waters, and the potential effects on sea-level rise, all part of an integrated collaborative project. Mikucki, along with graduate student Alicia Purcell, studied how organisms from Subglacial Lake Whillans may differ from those in the Grounding Zone.
“We hope the data will give us a better picture of how the subglacial environments are connected, as well as under-ice-shelf productivity. This will allow us to predict first responders to a warming climate,” Mikucki said.
These complicated analyses will take years to complete. And even then, the researchers say, their work may never truly be finished due to the constantly changing conditions. It’s just another part of the job for the scientifically curious.