Rapid Wasting

The phenomenon of rapid loss of coral tissue and destruction of coral skeleton from several species in the Netherlands Antilles was first called to the attention of scientists by Rolf Bak and Kalli De Meyer in December 1996. As of February 1998, observations indicate that it is a condition associated with parrotfish predation. In addition, an as yet unidentified fungus has been found at the scar surface of the corals. The condition is now known as rapid wasting.

Rapid wasting of Montastraea annularis off Bonaire. Photo by J. Cervino.
Appearance	Irregularly shaped, often large, patches of bare white skeleton appear on the surface of colonies of star coral (most commonly the columnar Montastraea annularis) and the brain coral Colpophyllia natans. The exposed skeletal surfaces are crumbly, often with the free edges of septa and pali missing or appearing to have eroded, with the result that the skeleton is depressed several millimeters to centimeters below the rest of the colony surface. The tissue margin can appear pale. The boundary between the skeleton and normal-appearing tissue is fairly sharp. In early intermittent observations, it appeared that tissue loss advanced across the surface of the colony at the rate of several centimeters (2-3 inches) per day; usually stopping when the patch was from 5 to 50 centimeters (2 to 20 inches) across on star coral, or continuing until the tissue was completely lost from the colony on brain coral.
Cause	Examination of samples of tissue and skeleton from affected coral colonies revealed a fungus on the bare skeletal surface adjacent to, and extending into, the coral tissue. These observations initially suggested that the fungus was responsible for the tissue loss. More recently, Andy and Robin Bruckner, along with James Cervino, have documented the fact that terminal-phase males of the stoplight parrotfish Sparisoma viride were attacking the corals repeatedly. These parrotfish are known to feed on coral tissue, producing extensive scrape marks and destruction of tissue and skeleton. Parrotfish are not common, however, at all locations where the condition has been observed. Other reports include similar tissue loss occurring without signs of fish feeding and in locations where parrotfish appear to be absent. There are also sites where parrotfish are present, but there are no signs of rapid wasting.
Terminal-phase male stoplight parrotfish biting a head of M. annularis. Photo by A. Bruckner.
Future research	Scientists from the University of Groningen who have been studying this parrotfish for years off Bonaire agree that perhaps something has recently changed the behavior of the parrotfish so that more corals are being attacked more frequently. However, the fungus is still an intriguing component of current research. Several groups of scientists are now collaborating to: identify the fungus, determine whether the fungus is contributing to the rapid loss of tissue and skeleton destruction, see whether the parrotfish might be contributing to the distribution of the fungus, and explore factors that might be changing the parrotfish behavior.
Distribution	Florida Keys and Caribbean (Netherlands Antilles, Colombia, Venezuela,Virgin Islands, Grenada, Tobago, Mexico, Grand Cayman).
Impact	Corals on reefs off the Netherlands Antilles appear to be most affected at this time, however, the number of affected corals may be decreasing. The eroded skeleton is eventually overgrown by filamentous green algae or red cyanobacteria.