A new study has found that many microbes are able to cross the Pacific Ocean on dust plumes.
"Over 70 million tons of Asian aerosols—mostly dust—reach our continent every year," says David Smith, from the University of Washington and lead author on the paper which is published in the journal Applied and Environmental Microbiology.
"There could be thousands of microbes per gram of dust. Do the math. The number is staggering. Distant continents are essentially sneezing on each other."
From an observatory perched high on the side of a snow encrusted volcano, Mount Bachelor in Oregon, the scientists collected samples from two large dust plumes that had travelled from Asia.
By analysing the DNA collected in the dust samples, the team found more than 2,100 unique species of microorganism compared to a previous finding of just 18. Around half were bacterial and the other half fungal, and could be traced back to Asian soils. They also detected archaeic bacteria, a domain of life that is distinct from most bacteria found on earth, which have never been found in our atmosphere before.
"It’s a small world. Global wind circulation can move Earth’s smallest types of life to just about anywhere," Smith says.
"Now when I look at the clouds, I see microbial sanctuaries," he adds.
While most of them were dead or harmless to human, Smith and his team did uncover several species that are able to form spores that allow them to hibernate in harsh conditions, making it possible to survive the long-distance travel.
"I think we’re getting close to calling the atmosphere an ecosystem," he says.
"Until recently, most people would refer to it as a conveyor belt, or a transient place where life moves through. But the discovery of so many cells potentially able to adapt to traveling long distances at high altitudes challenges the old classification."
Collecting the samples themselves was a physical challenge for the scientists. Mount Bachelor is an extremely cold environment and one of the windiest mountains in North America.
"Some summit days were an endurance marathon. Wearing latex gloves when it's 20 degrees below zero is not fun. But it was a worthwhile sacrifice for science, and I would happily do it again," says Smith.