Epidemics in animal populations, called epizootics, are a serious threat to the health of coral reefs worldwide. Recent observations of epizootics affecting sea urchins and corals show that diseases on reefs can devastate their target populations and act as agents of rapid and dramatic community change. Marine pathologists and microbiologists are attempting to identify the causes of infection, but the pathogens responsible for most diseases affecting reef organisms remain elusive. These difficulties complicate efforts by scientists and managers to study outbreaks and to determine if control measures are warranted. It is becoming clear, however, that human activity is at least partially responsible for disease outbreaks on coral reefs over the past decade.
Corals are colonial animals related to sea anemones.
They lay down the limestone foundations of coral reefs. Coral reefs are important because they protect tropical shorelines from damaging storm waves, and because they provide habitat for many of the fish and invertebrate species that feed a substantial proportion of the world's population. Like all living organisms, corals are prone to diseases of various sorts. A few long-term ecological studies of coral reefs suggest that the incidence of disease has risen over the past several decades. In most cases, however, historical information does not exist, and it is difficult to determine whether the increase in disease is real or simply a reflection of increased research activity.