Enigmatic outbreaks of disease have ravaged the coral reefs of Florida and the Caribbean, among Earth's richest ecosystems. Eugene Shinn, a coral researcher with the U.S. Geological Survey in St. Petersburg, Florida, may have found the culprit: an environmental chain reaction touched off by drought 3,000 miles away in western Africa.
The volume of African dust blown across the Atlantic has grown substantially over the last 25 years, to several hundred million tons a year. At the same time, the mortality rate among Caribbean coral reefs has also risen sharply. Shinn believes the corals' declining health is caused by fungal spores and bacterial cysts that hitch a ride on the dust. In 1998, scientists identified a soil fungus as the cause of an epidemic that decimated the sea fan population across the Caribbean basin. The fungus probably came from the Sahel, a semiarid region of western Africa that was experiencing drought at the time. Deforestation and desertification are making the dust problem worse, so human activity may be harming delicate corals even in places where pollution has not injured them directly.
Dust blowing from African fields may be killing corals thousands of miles away.Photo by Orbimage, The SeaWIFS Project/NASA/Goddard Space Flight Center