Skeletal Eroding Band

Skeletal eroding band (SEB) is a disease of corals that appears a black or dark gray band that slowly advances over corals, leaving a spotted region of dead coral in its wake. It is the most common disease of corals in the Indian and Pacific Oceans, and is also found in the Red Sea.

So far one agent has been clearly identified, the sessile heterotrich (ciliate) protozoan Halofolliculina corallasia. This makes SEB the first coral disease known to be caused by a protozoan or any eukaryote. When H. corallasia divides, the daughter cells move to the leading edge of the dark band and produce a protective shell called a lorica. To do this, they drill into the coral's limestone skeleton, killing coral polyps in the process.

A disease with very similar symptoms has been found in the Caribbean Sea, but has been given a different name as it is caused by a different species in the genus Halofolliculina and occurs in a different type of environment.

Skeletal eroding band is visible as a black or dark gray band that slowly advances over corals, leaving a spotted region of dead coral in its wake. The spotted area distinguishes skeletal eroding band from black band disease, which also forms an advancing black band but leaves a completely white dead area behind it.

Skeletal eroding band was first noticed in 1988 near Papua New Guinea and then near Lizard Island in Australia's Great Barrier Reef, but was regarded as a gray variant of black band disease, as were instances off Mauritius in 1990. Surveys in 1994 in and around the Red Sea first identified the condition as a unique disease. It is now considered the commonest disease of corals in the Indian and Pacific Oceans, especially in warmer or more polluted waters.

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