SYDNEY, Nov. 19 (Xinhua) -- Coral coverage has declined across the northern region of Australia's Great Barrier Reef (GBR) as a result of climate change and cyclones, government scientists said on Tuesday.
New data published by the Australian Institute of Marine Science (AIMS) revealed that coral cover has declined on 12 of 19 reefs surveyed in the northern region of GBR between August and October.
Scientists from the AIMS Long Term Reef Monitoring Program (LTMP) found that coral coverage on the 12 reefs has declined by 11-72 percent following a series of disturbance events during the summer of 2023-24.
More than a third of hard coral cover -- a measure of the percentage of live coral on the reef surface -- was lost in one sector, marking the largest annual decline for the sector since AIMS monitoring began 39 years ago.
Scientists attributed the widespread decline to an extensive mass coral bleaching event, two cyclones and flooding that affected the reef between December 2023 and March 2024.
Coral bleaching is a phenomenon that occurs when ocean temperatures rise and coral under heat stress expel the symbiotic algae living in their tissue, turning the coral completely white. Coral that has been bleached is not dead but is more likely to starve and can take years to recover.
The 2024 mass bleaching event affected the southern, middle and northern sections of the GBR and was the fifth such event in the last eight years.
"During February and March 2024, all the reefs we recently surveyed in this north Queensland region were subjected to levels of climate change-driven heat stress that cause bleaching," Mike Emslie, leader of the LTMP at the AIMS, said.
"The heat stress got so high in some areas that mortality is not a surprising outcome. Tropical Cyclones Jasper and Kirrily also exposed many to wave heights likely to cause damage to corals," he said.
The LTMP team is currently collecting data on the reefs in the southern region of the GBR. ■