Unpredictable Fungi

   
 

“I think that’s a fascinating possibility,” says Gene Shinn, a scientist with the U.S. Geological Survey’s Coastal and Marine Geology Program, based in Florida. Shinn and his colleagues have been culturing bacteria from African Dust blowing over the Caribbean for many years, linking the decline of Caribbean coral reefs in the 1970s, 80s, and 90s to bacterial infections brought over the sea with Saharan dust. While the air samples they collect almost always contain some bacteria that have hitched a ride across the Atlantic on the dust particles, Shinn says the presence or absence of fungi is unpredictable.

“Sometimes there are fungi in the samples, and sometimes not. We really had no idea why this was the case. We never considered smoke as a possibility, but there is periodic widespread biomass burning that takes places in the African Congo, and that smoke could be coming across the Atlantic mixed with dust. Here in Florida, we also get a lot of the smoke from fires in Central America. We have felt all along there had to be some additional factor explaining the fungi, and it’s intriguing to think this could be it.”

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  Model Aerosol Data from May 2, 2002

The possibility of the microbes traveling with the smoke isn’t farfetched, says Shinn. “That dark smoke will act as an ultraviolet shield for the fungi, protecting them from UV damage.” Even if the spores went high into the atmosphere, it’s quite possible they could remain sufficiently protected from the Sun’s ultraviolet rays to still be viable when they come back to Earth.

The presence of viable fungal spores in smoke certainly raises the possibility that burning pastures, crops, and trees that are infected with fungal diseases might not be a good idea. Such burning is practiced all over the world. If spores are released in smoke, diseases could spread as far as the smoke does.

On the other hand, many kinds of fungi are beneficial—even essential—for vegetation. They recycle nutrients into the soil by decomposing dead vegetation. Certain plants and trees have developed a partnership with fungi that “infect” their roots, with each one providing the other with nutrients that the other can’t get on its own (or can’t get as well), while doing each other no harm. If spores from these beneficial soil fungi could escape the reach of the flames with smoke and then settle back down after the fire dies back, they might speed up the recovery of the burned landscape.

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Dust and smoke travel all over the world. This global view shows aerosol optical depth on May 2, 2002, when smoke from Central America was blowing over Texas. The animation shows the movement of aerosols from their sources. Dust frequently originates in northern Africa and Asia, while smoke (less dense than dust) comes from seasonal fires in Central America and southern Africa.

    animations:
  • small (300 kB Quicktime)
  • large (2.1 MB Quicktime)

(Image and animation by Robert Simmon, based on GOCART Data)

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