As a result, simply recog-nizing whether a coral is healthy or sick can be extremely difficult, even for practiced researchers. Last month at a meeting of the Association of Marine Laboratories of the Caribbean held in San Jose, Costa Rica, Goreau spoke at a special daylong session devoted to coral diseases, one of the first chances researchers have had to exchange informa-tion on the problem. Scientists say they have no idea why diseases are exploding on corals now. Some speculate that multiple stresses, like bleaching, sedimentation and pollution, have pushed corals to the breaking point so that they are now unable to fend off diseases that they have fought off in the past. With the scant and scattered information researchers have so far on where the diseases are, there seems to be little sense to their spread, with some pristine reefs succumbing to disease while other much more polluted reefs remain healthy.
Most diseases are new.
They don't correlate with each other or any known envi-ronmental stress. In Bonaire, rapid wasting disease is having a devastating impact, yet the reefs there are so clean. Others have suggested that perhaps erosion and the dumping of sewage and other wastes into the sea has brought a whole host of new pathogens in contact with corals and some are taking hold. While the notion that terrestrial pathogens might begin underwater attacks on corals might seem far-fetched, researchers say there is evidence that at least one of the newly emerging diseases, sea fan disease, is caused by an organism that invaded from land. Discovered just four years ago, this disease of soft corals is now widespread in the Caribbean and has been shown to be caused by a highly opportunistic fungus called Aspergillus.