Grief on the reef

Natural History, Nov, 2002 by Stephan Reebs

Mysterious diseases have been striking reef-building corals worldwide. One of the most serious is white pox, an ailment that kills coral tissue, leaving behind the irregular white lesions for which the disease is named. Its victim is the elkhorn coral (Acropora palmata), an important Caribbean species that provides most of the reef structure in shallow water. Between 1996 and 1999 a team of biologists led by Kathryn L. Patterson of the University of Georgia in Athens documented, on average, an 85 percent loss of elkhorn coral on Florida reefs. Moreover, the workers observed, the disease spread among neighboring elkhorns, suggesting the culprit was an infectious agent.

Patterson and her colleagues have identified the agent as Serratia marcescens, a bacterium that can live freely in water but is also common in the intestines of various animals, including people. The finding raises the specter that untreated sewage dumped into the sea may be contributing to coral loss. And global warming will not help matters: the investigators have also reported a link between infection and water temperature. The immediate future for elkhorn coral could be bleak indeed. ("The etiology of white pox, a lethal disease of the Caribbean elkhorn coral, Acropora palmata," Proceedings of the National Academy of Sciences 99:8725-30, June 25, 2002)

Stephan Reebs is a professor of biology at the University of Moncton in New Brunswick, Canada, and the author of Fish Behavior in the Aquarium and in the Wild (Cornell University Press).