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Life thrives in ice-covered Antarctic lake
Braving ice-cold water pays off for research team who discover diverse microbial life flourishing at the bottom of an Antarctic lake.
Museum scientist Dr Anne Jungblut is part of a team of researchers who braved the dark, frigid depths of an Antarctic lake to describe the microorganisms that live there.
The results will be published this week in the journal Applied and Environmental Microbiology.
The bottom of the permanently ice-covered Lake Fryxell might seem an unlikely place to find life, but the calm waters provide such a stable environment that the level of diversity among microorganisms rivals the species richness found in tropical rainforests.
Lake Fryxell is an ice-covered lake in the McMurdo Dry Valleys, Antarctica. Unaffected by wind or other disturbances, it provides a stable environment in which microbial life can flourish.
Complex ecosystem
The researchers found that microbial communities differ greatly across the lake floor, both in structure and the species found within them. This is due to the varying levels of oxygen, sulphide and light at different depths.
The results potentially mean that microbes could be used to understand the impact of climate change on Antarctic lakes. Dr Anne Jungblut, Researcher in Botanical Diversity at the Museum and lead author of the study, explains:
'We found a remarkably complex ecosystem in which the microbial communities responded to changes in water chemistry and light conditions. This suggests that microbial communities might be indicators of climate-driven changes in Antarctic lakes.'
The team, made up of researchers from the Museum, University of Canterbury (New Zealand), University of California Davis and Louisiana State University (USA), faced challenging conditions to survey the bottom of the lake. They had to drill through around 4.5 metres of ice and then faced water as cold as 0oC. Experienced divers in the group could still only stay in the water for around 30 minutes at a time.
Researchers surveyed the gently sloping lake floor at between 8-11 metres depth by measuring light levels and water chemistry. They also photographed and took representative samples from the microbial communities for analysis in the lab, including DNA sequencing.
When microbes ruled the Earth
The scientists were surprised to find such rich microbial films on the lake floor. One type of microorganism present were cyanobacteria, which rely on sunlight for photosynthesis. Several metres of ice and water block most sunlight, so the presence of cyanobacteria suggests they may have evolved to cope with minimal light, and to survive the complete darkness of the Antarctic winter.
Dr Jungblut comments, 'It's possible that microbial life similar to that in Lake Fryxell dominated life on the early Earth for millions of years.'
A study published earlier this year, co-authored by Dr Jungblut and based on the same set of sample data, looked at the 'oxygen oases' formed by cyanobacteria in Lake Fryxell. It reported that the cyanobacteria photosynthesise and create a thin layer of oxygenated water in the otherwise oxygen-free waters along the lake bottom.
The authors suggest this as a model for similar 'oxygen oases' that may have existed up to 2.8 billion years ago, around 400 million years before oxygen levels began to soar at a global level.