White Pox

Another disease of the elkhorn coral was discovered in 1996 by Craig Quirolo and Jim Porter on reefs off Key West in the Florida Keys, with indications that loss of coral tissue due to the disease had begun two years before. Based on observations made during monitoring surveys during the summer of 1997, the disease has become epizootic on Florida Keys reefs. It is called white pox.

White pox on elkhorn coral, in the Florida Keys Photo by G. Burnham.
Appearance	This disease is characterized by the appearance of irregularly-shaped patches of bare white skeleton. The patches can occur on the surface or undersides of branches. The tissue appears to peel off unevenly, but an even margin has also been found. The rate of tissue disappearance is unknown, but appears to be rapid, since the skeleton usually begins to be fouled by filamentous algae within a few days and the freshest patches can be several square inches (tens of square centimeters) in area but still have bare white skeleton. Gastropod predators have not been seen on most affected colonies of elkhorn, Acropora palmata.
Close-up of White pox on elkhorn coral, in the Florida Keys Photo by J.W. Porter.
Appearance - continued	Patches can also be seen in which the loss of coral tissue appears to be slowing. Filamentous algae colonize the bare skeleton and the region of bare white skeleton then forms a band around this patch of algae. Some patches have also been observed in which the coral tissue and skeleton is showing regrowth (a translucent white "lip" of tissue and skeleton) and covering the algal patch.
Cause	The cause is unknown. Several scientists are currently studying this disease.
Distribution	Florida Keys, especially the lower Keys and reefs off Key West.
Impact	By October 1996, white pox appeared to have killed more than half of the elkhorn coral at Eastern Dry Rocks and the disease has spread north and eastward along the Florida Keys and has been seen in the Bahamas.