Black band disease

Example of black band disease progression on a colony of Diploria strigosa.

Black band disease is a coral disease in which corals develop a black band. It is characterized by complete tissue degradation due to a pathogenic microbial consortium. [1] The mat is present between apparently healthy coral tissue and freshly exposed coral skeleton.

Appearance

Black band disease on a brain coral in Caribbean Sea near Bahia de la Chiva on the island of Vieques, Puerto Rico

Black band disease was first observed on reefs in Belize in 1973 by A. Antonius, who described the pathogen he found infecting corals as Oscillatoria membranacea, one of the cyanobacteria. [2] The band color may be blackish brown to red depending on the vertical position of a cyanobacterial population associated with the band. The vertical position is based on a light intensity-dependent photic response of the cyanobacterial filaments, and the color (due to the cyanobacterial pigment phycoerythrin) is dependent on the thickness of the band. The band is approximately 1 millimeter (0.04 in) thick and ranges in width from 1 millimeter (0.04 in) to 7 centimeters (2.8 in) White specks may be present on surface, at times forming dense white patches. The pathogenic microbial mat moves across coral colonies at rates from 3 millimeters (0.12 in) to 1 centimeter (0.4 in) a day. Tissue death is caused by exposure to an hypoxic, sulfide-rich microenvironment associated with the base of the band.

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