The Black Band Disease of Atlantic Reef Corals

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Abstract
The cyanophyte(Cyanobaclerium)that causes black band disease of Atlantic reef corals is described under the namePhormidium corallyticum, new species (familyOscillatoriaceae), and its generic placement is discussed from the standpoint of the GEITLERian (classical) and Drouetsystems. Distinguishing characters include densely interwoven filaments that form a blackish mat and trichomes without significant cell wall constrictions, almost isodiametric cells (4.2 μm mean width, 4.0μm mean length) tapering end cells, and thin (0.1 μm or less) mucilaginous wall coating. Transmission electron microscopy shows typical cyanophyte cell walls, sheath, nucleoplasm, and cytoplasmic inclusions, but an unusual thylakoid of straight, and, as seen in cell cross section, radiating lamellae. The dark coloration is due to a high concentration of phycocyanin and some phycoerythrin. The species is similar toOscillatoria(=Phormidium) submembranacea, which differs in several morphological features and does not infect coral tissue. It is concluded thatPhormidiumshould be used for this and related species that have external mucilage but not the distinct sheath found inLyngbya.