International Society for Reef Studies Statement on Diseases on

Terry Done < tdone at
Thu Feb 4 14:43:03 EST 1999

Coral Reefs
Sender: owner-coral-list
Precedence: bulk
Reply-To: Terry Done <<tdone at>

Dear Coral-listers,

Below is a statement on diseases of corals and other important coral reef

compiled by the International Society for Reef Studies and released

The Society believes the statement is warranted at this time, following
its earlier

statement on Coral Bleaching published in its newsletter "Reef Encounter'
and on coral-list.

The International Society for Reef Studies (ISRS), consisting of over

members in over 50 countries, was founded in 1981 for the purpose of

promoting the production and dissemination of scientific knowledge and

understanding of coral reefs, both living and fossil. The ISRS

the scientific journal CORAL REEFS and holds periodic meetings around

world. Further information as well as membership details can be found

For all correspondence regarding this statement or other ISRS matters,

contact Dr Richard Aronson, Corresponding Secretary, at:-

raronson at

Submitted on behalf of the Society by

Terry Done

President ISRS


<bold><bigger><bigger><bigger>International Society for Reef Studies

Statement on Diseases on Coral Reefs

Released February 4 1999


Diseases of corals and other organisms are having significant, negative

impacts on the structure and appearance of coral reefs.  On some reefs,

the effects of disease have been of a similar magnitude to more familiar

disturbances, such as outbreaks of the crown-of-thorns starfish in the

Indo-Pacific and coral bleaching associated with elevated sea

temperatures.  A new scientific awareness of diseases on coral reefs

leads to a host of questions about the novelty of recently discovered

syndromes, the importance of observed trends toward increasing infection

rates, and the extent to which human activities are responsible.  This

statement, issued by the International Society for Reef Studies (ISRS),

summarizes current knowledge on the subject.  It was compiled by an ad

hoc group of scientists in ISRS, composed of individuals who are directly

or indirectly considering disease as part of their research programs.

Disease is a natural process that has been poorly studied in the oceans

because of its ephemeral nature.  Epidemics in animal populations,

called  epizootics, are a serious threat to the health of coral reefs

worldwide. Recent observations of  epizootics affecting sea urchins and

scleractinian corals show that diseases on reefs can devastate their

target populations and act as agents of rapid and dramatic community

change.  Marine pathologists and microbiologists are attempting to

identify the causes of infection, but the pathogens responsible for most

diseases affecting reef organisms remain elusive.  These difficulties are

complicating efforts by scientists and managers to study outbreaks and

decide if control measures are warranted.  It is becoming clear, however,

that human activity is at least partially responsible for disease

outbreaks on coral reefs over the past decade.

Corals are colonial invertebrates related to sea anemones.  They lay down

the limestone foundations of coral reefs, protecting tropical shorelines

and providing habitat for the many fish and invertebrate species that

feed a substantial proportion of the world's population.  Like all living

organisms, corals are prone to diseases of various sorts.  The incidence

of disease on coral reefs may be on the rise, but without historical,

baseline data it is difficult to determine if the observed increase is

real or simply a reflection of  increased research activity.  Recent

scientific reviews list four to six confirmed coral diseases in the

Caribbean region alone; other estimates, based only on observed symptoms,

run as high as fifteen.  Bacteria, fungi, and cyanobacteria ("blue-green

algae") are known to cause diseases in corals.   Sick and dying corals

are cause for concern, because coral death slows the rate of reef

construction.  Reefs devastated by disease (or by other causes of coral

mortality) may not be able to keep up with sea-level rise, which is

naturally slow but may be accelerating due to global warming.  And as

reefs degrade, fish and other seafood resources decline as well.

Three coral diseases--"white-band," "black-band," and "plague"-were

first reported in the Caribbean in the 1970s.  The first documented,

regional-scale epizootic, however,  affected the black-spined sea urchin,

Diadema antillarum.   In 1983-84, a disease carried by ocean currents

killed more than 95 percent of the Diadema throughout the Caribbean.

This epizootic clearly demonstrated that diseases can have major impacts

on reef ecology.  Before its mass mortality, Diadema was an important

herbivore: it ate fast-growing fleshy algae (seaweeds), keeping space

free for corals to survive and grow.  After the urchins died, algae

increased dramatically on many Caribbean reefs.  They colonized corals

that had been killed by hurricanes and by white-band disease.

Although the infective agent of white-band disease remains unknown, there

is some evidence that it is bacterial.  White-band disease infected

populations of staghorn and elkhorn coral (Acropora cervicornis and

Acropora palmata) throughout the Caribbean region in the 1980s and 1990s,

inflicting enormous losses.  Because Diadema also disappeared, seaweeds

rapidly colonized the dead coral skeletons, and as a result large areas

of Caribbean reefs have been covered with fleshy algae for over a

decade.  Paleontologists working in Belize recently uncovered evidence

that the epizootic of white-band disease is without historical precedent:

staghorn coral has not died off before on a regional basis in at least

several thousand years. Staghorn and elkhorn corals are major

constructors of reef framework, and their loss could slow the rate of

reef growth in the Caribbean.

Many marine scientists suspect that human activities, such as pollution

and changing patterns of land use, promoted the spread of  white-band

disease in Florida and the Caribbean.  There is little evidence for a

human connection, however, other than the historical novelty of the

outbreak.  Eutrophication, the enhanced input of nutrients by humans, may

be an important source of stress to reef organisms.  Eutrophication may

compromise disease resistance, allowing opportunistic infections to take

hold and new diseases to emerge.   A fungal infection of sea fans appears

to provide a link to human activity.  The fungus, Aspergillus sydowii,

has infected large populations of sea fans in the Florida Keys and

throughout the Caribbean.  Aspergillus sydowii is thought to be a

land-based fungus that has invaded the marine environment via the

sediment in terrestrial runoff.

Reliable information exists for two other diseases: black-band disease

and "plague type II." Black-band disease, caused by a consortium of

bacteria (including cyanobacteria) attacks and kills massive,

head-forming corals.  Black-band disease could pose a serious threat to

populations of brain corals and star corals, which, like the Acropora

species, are important components of reef framework in the Caribbean.

Plague type II attacks head corals in Florida, but it has also been

observed elsewhere in the Caribbean.   In this case, rigorous

microbiological work showed that the disease is caused by a single

bacterium, a new species of Sphingomonas.

Other epizootics are killing corals and many other important species on

reefs of the Pacific, Indian and Atlantic Oceans.  Black-band disease and

white-band disease have now been identified on reefs throughout the

tropical Indo-Pacific, including the Red Sea, Mauritius, the Philippines,

Papua New Guinea, and the Great Barrier Reef of Australia.  In the

Arabian Gulf, the newly discovered yellow-band disease is affecting up to

75 percent of the coral colonies in local populations.   In addition,

diseases of algae, sponges, and fish have been and continue to be

Reefs throughout the world were stressed by unusually high sea

temperatures in 1997-98, and the worldwide episode of coral bleaching

that resulted may render corals more susceptible to disease.  In the

Mediterranean, bacterial infections are associated with bleaching, and

disease outbreaks have been linked to predation by coral-eating snails in

the Red Sea.  The causal connections among bleaching, predation, and

disease remain obscure, however.

The role of disease on coral reefs and possible interactions with

environmental influences should be a research priority over the next

several years.  Despite the frustrating inability to identify pathogens

in most cases, reef scientists have detected symptoms that could

represent over a dozen new diseases.  Diseases are now recorded as part

of standardized reef monitoring programs throughout the world, including

the Caribbean Coastal Marine Productivity (CARICOMP) Program, the

worldwide Reef Check, the Atlantic and Gulf Reef Assessment (AGRA)

Program, and a variety of government and private programs in Australia.

Because corals grow slowly, live for decades to centuries, and reproduce

sporadically, today's epizootics will probably have consequences that

reach far into the future.  Multidisciplinary efforts, combining

microbiology, coral physiology and pathology, ecological monitoring, and

paleontology, will be necessary if we are to understand what is happening

and devise management strategies in response.  The International Society

of Reef Studies endorses existing government and private funding of

multidisciplinary programs to promote research on the changing nature of

coral reefs.  The Society recognizes the need for an increased level of

support if the many threats to reefs worldwide are to be understood and



Dr Terry Done

Australian Institute of Marine Science

PMB #3 Mail Centre,

Townsville Qld          4810


Phone 61 7 47 534 344

Fax   61 7 47 725 852

email: tdone at

More information about the Coral-list-old mailing list