A scientist points out the signs of sea fan disease - discoloration and disintegration.

The coral reefs of the Caribbean delight the eye and the imagination. But they are more than just divers' playgrounds. Reefs are also the rain forests of the ocean, home to numerous and diverse species, all of which depend in some way on the corals for survival.

In "Dust Busting," coral experts Gene Shinn, Ginger Garrison and Garriet Smith take Alan snorkling off St. John in the U. S. Virgin Islands. It's soon obvious there's trouble in paradise. Beautiful sea fan corals have literally been eaten away, while other types of once-colorful corals are covered in white patches. What's killing the coral?

To find out, the scientists have taken samples of sick sea fan corals from six different islands. The infected corals, it turned out, were loaded with fungi and bacteria. But only one pathogen infected all the sea fans- a common soil fungus called Aspergillus.

The fungus Aspergillus is the culprit behind the coral-killing plague.

Images of the Earth taken from the Space Shuttle provide a clue to the origins of this fungus. A brown haze can be seen stretching from Africa across the Atlantic. The haze is dust, millions of tons of it, blown off new African farmland and carried on the trade winds to the Caribbean. That dust could deliver a constant dose of the soil fungus to the water and to the coral.

More recently, Gene Shinn has discovered a second coral type, called the sea whip, which is also falling prey to Aspergillus. And he's hot on the trail of a possible culprit behind coral bleaching - yet another soil microbe. The Caribbean coral diseases are turning out to be an extraordinary example of how alien species can behave in unexpected ways in a new environment.

For more on this topic, see the web feature:
Algae Alert