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CORAL DISEASE

F6

What Is It?

BENCHMARK

Coral disease refers to a negative deviation from

(Preliminary) Yearly reports of disease

(Preliminary)

a coral's normal state or condition.  This deviation

incidence

incidence less than 3 to 4%.

can include functional or structural impairment. Coral

TA R G E T

diseases are often characterized in terms of their

identity (e.g., black band disease) and their prevalence

(Preliminary) Yearly reports of disease

(Preliminary)

(the percentage of total colonies affected).

incidence

incidence of approximately 1% (or less).

Coral diseases can kill coral tissue quickly (up to 2

RED FL AG

cm/day), which is much faster than average coral

Coral disease prevalence > 5% is of

Coral

growth rates (~2 cm/year).

concern and should be monitored to

Why

Why Do We Measure It?

track potential effects.

track

Disease is a signal of coral stress and is a potential

cause of mortality. This indicator is central to the

How Do We Measure It?

concept of reef health, as health can be considered,

in part, as the absence of disease.

Disease prevalence is expressed in terms of the

percentage of total colonies affected3,8. Since it is

Disease is an effective indicator of condition,

difficult to identify a specific disease, diseases are

particularly when combined with estimates of partial

distinguished using color categories21,22:

mortality and other measures of coral condition

(e.g.,  remnant  bleaching,  predation,  physical

· BB = Black band. Concentric/linear band, maroon

damage). Diseases have played a significant role in

to black, 1-30 mm wide.

the widespread mortality of important reef-building

· WB = White band (Acropora only). Exposes skeleton

species in the MAR over the last couple of decades.

in a band advancing from the base toward the

The main concern is that coral diseases are infecting

branch tips.

a greater number of coral species, increasing in

· WS = White pox (or spot), patchy necrosis (Acropora

frequency and distribution, and are spreading to new

only). Irregular lesions on the top sides of branches,

areas faster than previously observed. Increases in

5-10 cm diameter. Re-infection results in a mosaic of

coral disease have been associated with increased

recently exposed and older, algae-covered lesions.

sea surface temperatures and bleaching. It is still

unclear whether bleaching causes corals to be more

· WP = White plague. Denuded skeleton is intact. The

susceptible to opportunistic pathogens, or if pathogens

disease front is a sharp line; no microbial community

normally present exacerbate levels of bleaching and

is visible.

bleaching-related mortality. Some coral diseases may

be linked to human sewage and other contaminants,

· RB = Red band. Dense band, maroon to red, 1-25

as well as increasing temperatures30.

mm wide. Less common than black band disease.

· YB = Yellow band, yellow blotch. Concentric pale

yellow band, living tissue. Small spot in the center

is recently killed and becomes large as the disease

expands outwards.

· DS = Dark spot. Irregular dark patches of tissue.

Surface is often slightly depressed.

· UK = Unknown.

Ken Marks

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