Washington - Dust plumes high in the atmosphere are wafting a vast number of microorganisms from Asia, across the gaping Pacific, into North America.
Scientists detected more than 2,100 unique species compared to only 18 found in the very same plumes using traditional methods of culturing. They have been able to gather enough biomass in the form of DNA to apply molecular methods to these samples.
"It's a small world. Global wind circulation can move Earth's smallest types of life to just about anywhere," says David J. Smith, biologist from the University of Washington, the journal Applied and Environmental Microbiology reports.
It has been estimated that about 7.1 million tonnes of aerosols -- dust, pollutants and other atmospheric particles, including microorganisms -- cross the Pacific each year, according to a Washington statement.
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 18 km, is where almost all our weather occurs.
Co-author Daniel Jaffe, professor at Washington-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 half fungal -- originated from soils and were either dead on arrival or harmless to humans.
A few fungal species have been associated previously with crop wilt but scientists had no way of determining if any crops were affected during either plume event.
Interestingly, Smith says, two of the three most common families of bacteria in the plumes are known for their ability to form spores in ways that they can hibernate safely during harsh conditions, making them especially well adapted to high altitude transport.