A surprising number of microorganisms 99 percent more kinds than had been reported in findings published just four months ago are leaping the biggest gap on the planet. Hitching rides in the upper troposphere, they're making their way from Asia across the Pacific Ocean and landing in North America. For the first time researchers have been able to gather enough biomass in the form of DNA to apply molecular methods to samples from two large dust plumes originating in Asia in the spring of 2011. The scientists detected more than 2,100 unique species compared to only 18 found in the very same plumes using traditional methods of culturing, results they published in July.
"The long-range transport and surprising level of species richness in the upper atmosphere overturns traditional paradigms in aerobiology," says David J. Smith, who recently earned his doctorate at the University of Washington in biology and astrobiology. He's lead author of a paper in the current issue of the journal Applied and Environmental Microbiology.
"It's a small world. Global wind circulation can move Earth's smallest types of life to just about anywhere," Smith said. It's been estimated that about 7.1 million tons (64 teragrams) of aerosols dust, pollutants and other atmospheric particles, including microorganisms cross the Pacific each year. The aerosols are carried by wind storms into the upper reaches of the troposphere. The troposphere, the layer of air closest to earth up to about 11 miles (18 kilometers), is where almost all our weather occurs.
Co-author Daniel Jaffe, professor at UW Bothell, has previously documented especially large plumes of aerosols in the troposphere making the trans-Pacific trip in seven to 10 days. The recent findings are based on two such plumes, one in April and the other in May of 2011, detected at Mount Bachelor in the Cascade Mountains of central Oregon.
Most of the microorganisms about half were bacterial and the other
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University of Washington