Dark spot syndrome: a scleractinian coral disease or a general stress response?

In the last decade, there has been a considerable increase in the number of different coral diseases described. In most cases, physical anomalies are named as coral diseases/syndromes and subsequently studied in varying degrees of detail. However, many of these conditions remain insufficiently characterized (Richardson 1998). One such syndrome is dark spots syndrome (DSS), otherwise referred to as dark spots disease. This affliction was first identified in the early 1990s and later described by Garzon-Ferreira and Gil-Agudelo (1998). It is characterized by purple, black, or brown lesions that are circular, ring-shaped or elongate and are found scattered across the coral tissue surface in varying densities or lining the coral tissue-algal boundary. The discoloration of tissue was reported as caused by an increase in zooxanthellae pigments (Cervino et al. 2001). Published records indicate that DSS primarily affects the species Siderastrea siderea, Stephanocoenia intersepta, and Montastraea annularis. Tissue mortality is not always associated with this syndrome (Borger 2003), but when it does occur, it proceeds at a rate of approximately 4 cm month super(-1). This study was designed to investigate DSS by conducting long-term monitoring of affected colonies and by utilizing digital photography to assess visual alterations of DSS blemishes over time. The goal was to gain insight into the status of DSS as a disease versus a general stress response of corals.