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Rare rainfall in the Atacama is deadly for its tiniest inhabitants

By Mara Johnson-Groh
December 11, 2018, 12:05:53 PM EST


The Atacama desert typically receives less than a half-inch of rain every year.Credit: Lukas Bischoff/iStock/Getty Images Plus

In the summer of 2017, after a freak rainfall, unusual lagoons appeared in the oldest and driest desert on Earth — the Atacama. In an area that usually receives less than a half-inch of precipitation annually, the temporary oases should have been a boon to desert life — but, alas, they weren't. Microbial life in the soil, which had adapted to hyperarid conditions over millions of years, quickly perished.

And they didn't go quietly: Up to 87 percent of the bacteria in the lagoons died after having "burst like balloons" from sponging up too much water in their newly aquatic environment, according to new research published online Nov. 12 in the journal Scientific Reports. Of 16 species identified in arid samples, only two to four survived the deluge to remain in the lagoons. One survivor was a hardy, newly discovered species of bacteria in the salt-loving genus Halomonas.

"Halomonas lives virtually everywhere on Earth — you go to your backyard and analyze the soil, and you'll find them there," said study co-author Alberto Fairén, an astrobiologist at the Center for Astrobiology in Madrid and Cornell University in New York. "They are a microbe highly adapted to salinity, which explains their rapid recuperation and adaptation after the rains to the new saline lagoons."

The Atacama, sandwiched between the Andes and a coastal mountain range in Chile, has been arid for an astounding 150 million years. In that time, several species of bacteria have become exquisitely adapted to the salty, nitrogen-rich environment, able to rapidly soak up the tiniest bit of moisture. When the heavy rains created flooded lagoons, the bacteria inadvertently sucked water through their membranes faster than their bodies could deal with it. The result: They burst open in what is known as osmotic shock.

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