Ancient life discovered under Antarctic ice
An ancient and unusual ecosystem, isolated from the outside world for thousands of years, has been uncovered deep beneath a salty lake in Antarctica, scientists have announced.
The unusual and extreme aquatic ecosystem was discovered in Lake Vida, a 5 km long lake in the cold Antarctic desert region known as the McMurdo Dry Valleys. The scientists said the find could give insights into life on Earth during the ice ages.
It also overturns earlier assumptions that Lake Vida was frozen solid. "That's an important conclusion because Lake Vida is in an area that has a fairly cold mean annual temperature," said Doran. "It actually pushes back our estimates of what it takes to freeze a lake ecosystem."
Drilling through the 19 metres of lake ice cover - a feat never achieved before - the team found a liquid lake of concentrated salt water. This brine, seven times saltier than seawater, allowed the water to remain liquid at -10°C.
"Lake Vida gives us an excellent model of how long a lake ecosystem can survive before you snuff it out by turning down the temperature," he said.
Antarctica's Lake Vida appears to represent a previously unknown ecosystem - a frigid, 'ice-sealed' lake. Frozen bacteria and algae were found in ice core samples taken from above the pool of brine; these came back to life after gradual melting. Carbon-14 dating showed them to be more than 2,800 years old.
Doran said the brine is likely to be at least that old, forming as salts settled down into it while thick ice grew outward from the sealed, freeze-resistant salty lake. The group believes the salty water may also harbour life.
"Any primary producers potentially living in the brine down deep are not getting sunlight, so they would have to be chemosynthetic, that is, getting energy from the surrounding chemicals instead of sunlight," said Doran. "The microbes frozen in the ice above seem to be life that was living shallow in the lake at some time, then water flowed on top of the thick ice cover and froze."
"The ice covers of these lakes represent an oasis for life in an environment previously thought to be inhospitable," said Professor John Priscu, an ecologist at Montana State University in the United States.
"These life forms may possess novel ice-active substances, such as antifreezes and ice nucleation inhibitors, that allow the organisms to survive the freeze-thaw cycles and come back to life when exposed to liquid water," he said.
The unusual lake is a product of the region's unique environmental conditions: summers warm enough to briefly flood the valley floors with glacial meltwater, combined with winters cold enough to create a permanent ice cap.
The area receives less than 10 cm of snow per year, and the average annual temperature hovers around -30°C.