Black Band Disease in Corals
Black band disease is a dark, sulfide-rich microbial mat that creeps across a coral, killing tissue and leaving bare skeleton behind it. Learn the cyanobacteria-led consortium that drives it, how the toxic band works, and the containment approach for aquariums.
What black band disease is
Black band disease (BBD) is a cyanobacteria-dominated, sulfide-rich microbial mat that migrates across coral colonies, degrading tissue. The mat is a consortium: photosynthetic cyanobacteria (classically Phormidium corallyticum; newer work identifies Roseofilum reptotaenium and genera such as Geitlerinema and Leptolyngbya), sulfide-oxidising bacteria (Beggiatoa), sulfate-reducing bacteria (Desulfovibrio) and other organisms.
How the band kills
The dark band, roughly 1 mm thick and ranging from 1 mm to 7 cm wide, sits between healthy tissue and bare skeleton. At its base a hypoxic, sulfide-rich microenvironment forms; sulfide is toxic to animal cells and drives the tissue death, and it is required to initiate the disease. The band advances across the colony at 3 mm to 1 cm per day, and its speed varies with temperature, light and pH. BBD-associated cyanobacteria can also produce the cyanotoxin microcystin.
Containment approach
- Identify the dark, migrating band with bare skeleton left behind it, distinct from a static algae patch.
- Isolate the affected colony to limit spread.
- Physically remove the band and improve water quality to disrupt the sulfide and hypoxia microenvironment that sustains it.
- Monitor the demarcation line daily, as the band can advance up to 1 cm per day.
Sources: pmc.ncbi.nlm.nih.gov ; en.wikipedia.org (Wikipedia, CC BY-SA 4.0)