St. Petersburg Coastal and Marine Science Center
Black-band disease (BBD) is one of the most easily identified coral diseases because of its distinctive appearance. The black band is a bacterial mat, consisting of cyanobacteria, sulfide-oxidizing and sulfate-reducing bacteria. As such, BBD is viewed as a polymicrobial disease, since all members of the microbial consortium must be present to cause tissue death on the coral. As the bacterial mat moves over the coral, the tissue is killed by the lack of oxygen, increased sulfide, and possibly also due to toxins produced by the cyanobacteria. As shown in the photos in this gallery, the black band is at the interface between the healthy coral tissue and the dead skeleton that remains as a result of the disease. BBD affects more than 40 species of coral and is found in marine waters all over the world. Click on a photo to see a larger version. Cåredit for all photos: USGS/Christina Kellogg.