Disease Strikes Great Barrier Reef

May 6, 2009 -- An epizootic -- the wildlife equivalent of a human epidemic -- of black band disease has appeared in the Great Barrier Reef, say Australian researchers.

Scientists, who have been monitoring the progress of the disease, say this the first time an epizootic of this type has been documented in Australian waters.

Black band disease has decimated coral populations in the Caribbean and researchers are concerned it could spread here.

Marine biologist Yui Sato of James Cook University in Townsville, Australia and colleagues reported their findings in the latest issue of Proceedings of the National Academy of Science.

Sato, who is a research student with the ARC Center of Excellence for Coral Reef, says the black band disease flourishes in warm seawater, killing coral as it eats through tissue, exposing the fragile skeleton.

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He is concerned that predicted warmer ocean conditions caused by global warming will lead to longer outbreaks and faster tissue loss. The researchers compared photos of 485 colonies of Montipora species -- a hard, plate-like coral -- with photos from two previous surveys to track coral death and infection.

Infectious diseases in reef building corals have emerged at an increasing rate throughout the last few decades. Sporadic occurrence or low prevalence had been documented in the Reef since 1993, but this is the first time big outbreaks had been found.

"It has not previously been documented like this with such a big impact on the coral assemblage," said Sato. "It shows impacts of the disease are greater than previously reported on the Great Barrier Reef and likely to escalate with ocean warming."

The researchers found that at least 10 percent of Montipora corals in the Great Barrier Reef were infected during summer with about 5 percent of those dying.

They also found that surviving coral were three times more likely to be reinfected than uninfected coral. This may be due to bacterial pathogens remaining in the colony or due to a compromised immune system.