The 2002 coral bleaching event

In 2002, the Great Barrier Reef suffered another coral bleaching event. It was not associated with extreme ENSO conditions, but the effects were worse than 1998, making it the worst on record for the Great Barrier Reef. Aerial surveys of more than 640 reefs found that nearly 55% of the reef area in the Great Barrier Reef Marine Park showed some degree of bleaching as a result of heat-stress. Not all reefs bleached as severely as others and the impacts of bleaching were not evenly distributed throughout the Great Barrier Reef.

The coral bleaching event in 2002 event was considered worse than the 1998 event because more reef area was affected. The most severe bleaching occurred on reefs closest to shore in both bleaching events, but the 2002 event affected a greater area of reefs further offshore.

Map showing bleaching on teh Great Barrier Reef as seen from aerial surveys in 2002.

The aerial surveys found that bleaching was most severe in the Princess Charlotte Bay region; near the Turtle Island Group; on inshore reefs from Cape Upstart to the Whitsundays, in some reefs in the Sir James Smith Group; and in the Keppel Island area. Moderate to very severe bleaching was seen inshore and offshore from around Cape Flattery to Mackay. Little or no bleaching was seen in the Far Northern Section from the tip of Cape York to the northern Princess Charlotte Bay area, in the Swains area and in the Capricorn Bunker Group.

Underwater surveys were used to confirm results from the air and determine whether corals were likely to recover from bleaching or would die. The underwater surveys found that few reefs escaped bleaching, but that most reefs recovered with only 5% of reefs suffering long-term damage. However, some reefs were devastated with 50-90% of corals dead at some sites.

Australia has been relatively fortunate in escaping widespread death of corals despite experiencing two major bleaching events in recent years. However, the devastation at some sites provides a vivid warning of what could happen if hot water events become more frequent and severe in the Great Barrier Reef region.

CRC Reef Research Centre Ltd was established and is supported under the Australian Government’s Cooperative Research Centres Program. Its mission is to plan, fund and manage world-leading science for the sustainable use of the Great Barrier Reef World Heritage Area. CRC Reef is a joint venture between Association of Marine Park Tourism Operators, Australian Institute of Marine Science, Great Barrier Reef Marine Park Authority, Great Barrier Reef Research Foundation, James Cook University, Queensland Department of Primary Industries and Fisheries, Queensland Seafood Industry Association, Sunfish Queensland Inc. The University of Queensland is an associate member.