The Significance of Coral Diseases

Although bacteria were first observed within coral tissue in the early 1900s (Duerdon, 1902) the first reports of disease affecting scleractinian corals did not appear until the early 1970s. Increasingly frequent observations of coral diseases in the wild have been given added importance by the lack of previous observations even on well-studied reefs. Therefore the possibility exists that the present widespread occurrence of coral diseases is a manifestation of a decline in the integrity of the wider marine environment. This possibility continues to fuel the production of an extensive and varied literature.

There is good direct (Gladfelter 1982; Aronson and Precht 1997) and indirect (Garzon-Ferreira and Zea, 1992) evidence that mortality arising from disease has modified the composition and structure of coral reefs across the Caribbean by removing common and locally abundant species. Furthermore the results of some field monitoring programmes do suggest that the occurrence of disease, at least in the Florida Keys, has increased dramatically in the last few years (Porter et al. 1999). For most of the world's reefs a consensus of opinion exists that conditions during the past 20 years have been very different to those prevailing during the two decades prior to 1980. Although the exact nature of this global environmental change remains unknown it is tempting to speculate, as many have done, that direct and indirect human impacts on reefs are responsible. However beyond tantalising glimpses provided by studies which have attempted to examine the relationship between disease and water pollution (e.g. Mitchell and Chet 1975; Antonius 1981) the role of anthropogenic influence is extremely unclear. Indeed this is beginning to be recognised as one of the most important yet most poorly understood aspect of coral diseases.