Green slime opens the door to the past
28 Sep 2015 by qwwqdccwwm.d qwwqdccwwm.d
Green slime at the bottom of an Antarctic lake replicates conditions that occurred on Earth 2.8-2.4 billion years ago, a new study finds.
A research team at the University of California in Davis used samples from the bottom of Lake Fryxell in the McMurdo Dry Valleys and discovered that cyanobacteria – bacteria that obtain their energy through photosynthesis – created conditions similar to the Great Oxidation Event when dioxygen appeared in the atmosphere.
“Lake Fryxell provides natural laboratories where impact on biogeochemical signatures can be investigated,” the researchers said in their paper.
In the study, published in the journal Geology, the team studied life in ice-covered lakes in the McMurdo Dry Valleys and discovered that the lakes in the valley typically contain oxygen in the upper layers but are usually anoxic – showing a depletion of dissolved oxygen – at depth.
Below the oxygen -rich zone, the scientists measured a 1-2mm layer of oxygen that has been generated by photosynthesising bright green bacteria. They believe the discovery is an ancient oxygen oasis where oxygenation was initiated before it became widespread around the planet.
“Something similar could have been happening billions of years ago. The thought is, that the lakes and rivers were anoxic, but there was light available, and little bits of oxygen could accumulate in the mats,” said Professor Dawn Sumner at the University of California.
They hope these findings will help geochemists understand chemical reactions between the oxygen oasis and the anoxic water.
“What is not clear is what happened in between, or how long the transition - called the Great Oxidation Event - lasted,” said Professor Sumner.
