Mystery Disease Kills Coral on Great Barrier Reef

TOWNSVILLE, Queensland, Australia, October 18, 2002 (ENS) - Scientists at the Australian Institute of Marine Science (AIMS) have confirmed the existence of coral disease on the world's longest reef, the Great Barrier Reef which stretches along Australia's east coast.

Researchers at the government institute do not have to travel far to see the giant reef - they just glance out their front door - but they have searched the world for a clue to the cause of the disease they have observed.

AIMS scientists working in the long term monitoring program say the disease they have documented is in a broad category known as White Syndrome. Soon they hope to learn exactly what White Syndrome is.

Cathie Page surveying infected coral on Yonge reef off Lizard Island. (Photo © Australian Institute of Marine Science)

"It doesn't fit the description of diseases found anywhere else in the world, so it might be specific to the Pacific," she says.

In the three years Page has been on the monitoring team, she has logged about 450 dives spanning 48 reefs.

She has seen White Syndrome kill at varying rates. "It could kill a colony of two metres (6.5 feet) in diameter in two weeks but in some other cases, it takes months to kill a large colony," she said.

The first record of coral diseases came from reefs off Belize and Florida in 1973. In 1993 coral diseases were noticed on the Great Barrier Reef. When the diseases worsened in the late 1990s, the long term monitoring team started documenting their activity.

In 1999 only seven reefs were infected with White Syndrome; in 2002 33 reefs were affected out of the 48 studied by the AIMS long term monitoring team.

The highest number of infected colonies within one reef was 101 in a 1,500 square meter area. That was on Carter Reef, an outer shelf reef in the Cooktown/Lizard Island sector. The syndrome killed those colonies infected and caused a decline in hard coral cover on this reef.

AIMS scientists together with researchers from James Cook University who are collaborating on the project have recorded the disease in northern waters during the winter months.

Outer-shelf reefs near Lizard Island off Cooktown in the northern Great Barrier Reef and the Capricorn Bunker reefs in the southern Great Barrier Reef are the worst affected areas.

White Syndrome has taken hold of this Tabulate Acropora coral. (Photo © Australian Institute of Marine Science)

Coral bleaching is also affecting the great reef, and scientists fear White Syndrome could be spreading more quickly in corals weakened by bleaching.

Coral bleaching is the name given to an event where coral expel their symbiotic algae due to extreme stress, such as unusually hot water, according to AIMS bleaching expert Dr. Terry Done. The bleached corals die if the stress is extreme or prolonged.

With rising water temperatures over the tropical summers, coral bleaching events are more widespread and happening more often, leaving little time for coral to recover.

"Bleached coral is not healthy and potentially more susceptible to diseases," said Page. "We don't know what's causing this disease. It's microscopic; it could be a range of things."

AIMS has sent samples of corals affected by White Syndrome away for testing. When the results come back, they will search for solutions that might save the corals of the Great Barrier Reef.