White Plague

Massive and encrusting coral species have been observed to lose their tissues, leaving behind bare white skeleton. Phil Dustan first reported this condition from the Florida Keys and called it white plague (WP). It has also been called "white-band disease," "white death," and "stress-related necrosis," but the roles of environmental stress and pathogens in the loss of tissue have not been adequately investigated. In the summer of 1995, rapid tissue loss was observed on many species of hard corals in the Florida Keys. In particular, the large starlet coral, Dichocoenia stokesii, was notably affected. This coral had been considered to be one of the hardiest western tropical Atlantic coral species.

White plague on large starlet coral, Dichocoenia stokesii, Florida Keys. Photo by S. Miller.
Appearance	Tissue disappears from massive, encrusting, and branching species of corals at the rate of one or more centimeters (about 3/8 inch to 4 inches) per day (Florida Keys 1995), leaving behind bare white skeleton. The receding tissue appears as a sharp line at the skeletal interface. This rate is much faster than that previously reported for white plague, a few mm per day (Florida Keys 1977 and elsewhere), (Dustan, 1977). Many species have been affected by this kind of tissue loss.
White plague on symmetrical brain coral, Diploria strigosa (on right), and lettuce coral, Agaricia agaricites (on left), Florida Keys. Photo by S. Miller.
Cause	Early studies indicated that the disease could be spread from one colony to another suggesting that a pathogen was involved (Dustan, 1977) or related to physiological stress or other factors (Antonius, 1981; Peters, 1984). Scientists mobilized by the University of North Carolina's National Undersea Research Center in Key Largo are studying the Florida Keys disease. The rapid loss of tissue is now called WP type II to distinguish it from the slower loss of tissue originally seen (WP type I). It appears to be highly infectious, possibly caused by a bacterium, and capable of spreading from one colony to another. The results of their studies should be available in the near future.
Distribution	Worldwide (WP type I). Florida Keys (WP type II).
Impact	Partial or complete loss of tissue from coral colonies (WP type I) has been reported from many localities. Complete or partial loss of coral tissue was observed from colonies of about 18 species in the Keys since 1995, including the relatively rare pillar coral, Dendrogyra cylindrus. The extremely rapid rate of tissue loss and the ability to cause mortalities in many species of corals make this malady a particular concern, not only for the Keys, but also for the rest of the tropical western Atlantic region.