Types
of Coral Disease and Their Identification
Red-Band Disease (RBD)
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Red-band
disease (RBD) resembles black-band disease. It is characterised
by the presence of a narrow band or line of filamentous cyanobacteria
(blue-green algae) and other microorganisms that separate coral
skeleton from live tissue. There are two types of RBD, referred
to as RBD-I and RBD-II. RBD-I has been observed on Agaricia,
Colpophyllia, Mycetophyllia and Stephanocoenia,
and sea fans Gorgonia ventalina.
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Lettuce coral
(Agaricia agaricites) with RBD. The thin cyanobacterial
filaments form a loose mat adjacent to healthy tissue.
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Close-up
of RBD on Gorgonia ventalina. The lower portion of
the sea fan has become covered with sediment and algae.
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Red-band disease is spreading from the base of this sea fan to
the top.
A
new RBD-I infection in brain coral, Meandrina meandrites.
Only a few cyanobacterial filaments are visible. The colony has
a small patch of denuded white skeleton that is becoming covered
by sediment visible in the lower right portion of the photograph.
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RBD-I
is most similar in appearance to BBD, in that it forms a distinctive
band that separates live coral tissue from bare white skeleton,
and it advances a few millimeters per day. Unlike BBD, the band
is more red to maroon in color, and the cyanobacterial filaments
are often more loosely organized and less mat-like.
Red-band disease may first infect a sea fan at the base of a colony
or from within the blade as shown here.
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Blushing star coral (Stephanocoenia intersepta) affected
by RBD-II. The cyanobacteria have formed a dense mat covering live
tissue.
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Boulder
brain coral (C. natans) with RBD-II.
A
second type, RBD-II affects massive scleractinian corals (D.
strigosa, C. Natans, M. annularis, M. cavernosa,
Porites astreoides and Siderastrea radians). RBD-II
is visibly different from RBD-I. During daylight, the filaments
spread out like a net in a diffuse fashion over live tissue and
bare skeleton; at night the band forms a compact balled-up mat
at the interface between live tissue and exposed skeleton.
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