Antarctic Lake: Key to Oxygen's Past

An oasis of oxygen found in green slime at the bottom of a Antarctic lake might help researchers better understand Earth's conditions two and a half billion years ago, before oxygen was common in the atmosphere. Thanks to a bacteria that evolved with the ability to photosynthesize, the Earth experienced a transition known as the Great Oxidation Event. However little is known about this event and how long it lasted, according to a release.

Dawn Sumner, professor and chair of earth and planetary sciences at the University of California-Davis, explained that this discovery in Lake Fryxell in the McMurdo Dry Valleys could be a modern example of such an ancient oxygen oasis, and will help geochemists figure out what to look for in ancient rocks. Summer is one of the authors of a study recently published in the journal Geology, which explains these findings further.

According to a news release, the researchers have been studying life in these ice-covered lakes for several years, since the microbes that survive in these remote and harsh environments are believed to be similar to Earth's first lifeforms and possibly those of other planets as well.

Sumner noted in the release that the lakes of the Dry Valleys generally contain oxygen in their upper layers, but become anoxic further down. However, during a dive below the oxygen zone they found bright green bacteria that appeared to be photosynthesizing.

After they took measurements, they found that the bacteria was actually generating a thin layer of oxygen just one or two millimeters thick. Sumner said this is something similar to what 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," she said in the release.

What's next? The researchers plan to examine the chemical reactions between the oxygen oasis and the surrounding anoxic water. This could benefit scientists identifying chemical signatures preserved in rocks.

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