Still recovering from the worst coral bleaching episode on record, the Great Barrier Reef is now battling disease called White Syndrome.

The Australian Institute of Marine Science reports that White Syndrome is slowly killing some corals and its prevalence is worsening in some areas of the Reef.

The AIMS Long-term Monitoring Program started surveying reefs for White Syndrome in 1999. Before this, the disease was considered rare. The surveys show it has spread from seven to 33 reefs over four years and has increased in abundance on outer reefs off Cooktown and the Capricorn coast.

While the overall impact of White Syndrome on the Barrier Reef is relatively small, scientists fear it could be just the beginning. Their greatest fear is the impact the disease could have on top of coral bleaching, which occurs in heat-wave conditions when stressed corals expel their symbiotic algae. Last summer's bleaching event was the worst on record, with 60% of the Great Barrier Reef Marine Park affected to some extent.

White Syndrome has mainly infected table corals to date, and generally starts at the base of the coral. It works its way up, eating away the live coral tissue. In some cases, it has killed entire coral colonies.

"In areas where White Syndrome is most prevalent, the disease can kill a colony two metres in diameter in about two weeks. In other cases, it can take months to kill a large colony," said AIMS benthic ecologist Cathie Page. "Some colonies are spared and only parts of them are infected."

Little is known about White Syndrome. Infected coral samples are yet to be examined in-house by AIMS microbiologists. Others have been sent to the United States for pathology tests. No one knows what causes the disease and it may, in fact, be a number of diseases.

Scientists know only that it is microscopic - a virus or bacteria or some other microorganism - and could be specific to the Pacific because it doesn't fit the description of diseases found elsewhere.

"These microorganisms might be taking advantage of corals weakened through bleaching, when they are more susceptible to disease."

The surveys undertaken by the AIMS Long-term Monitoring Program show a wide distribution of the disease, though it is most common on the outer reefs where the water is clear. Thus there's no evidence to link the disease with land-based pollution. This is contrary to the situation in other parts of the world, where coral diseases are often found in locations affected by coastal pollution such as sediment and nutrient run-off.

For further information contact
Cathie Page, AIMS Reef Monitoring Team, 
Phone: 07 47534229 or 
Email: c.page@aims.gov.au 

Theresa Millard, AIMS Science Communication, 
Phone: 07 47534250, 47534444, 
Mobile: 0409596271
Email: t.millard@aims.gov.au 

Check out our web feature story on coral disease at:
Pristine reefs affected by coral disease