Fourth global mass coral bleaching? Great Barrier Reef severely affected, corals seen dying 

A widespread coral bleaching event has engulfed the Great Barrier Reef (GBR), Australian authorities have confirmed. The reef is spread over an area larger than Italy.

The phenomenon was observed by aerial surveys conducted jointly by the Reef Authority with the Australian Institute of Marine Science (AIMS) over two-thirds of the GBR Marine Park. Experts also claimed that some of the corals are dying. 

The surveys showed that the bleaching gripped the reef in over 300 inshore, midshelf and offshore reefs, stretching from Cape Melville of Cooktown towards north of Bundaberg in the southern boundary of the Marine Park.

Reef Authority Chief Scientist Roger Beeden, in a media statement issued on March 8, said the results from the surveys are synonymous to the patterns of heat stress built up over summer. 

“The results are consistent with what we have seen with above-average sea surface temperatures across the Marine Park for an extended period of time,” he said, adding, “Aerial surveys of the Reef have revealed prevalent shallow water coral bleaching on most surveyed reefs.” 

Earlier on February 28, 2024, the scientists revealed that apart from other regions, the southern GBR was the most affected by coral bleaching.

A statement released by James Cook University, Australia on February 22 stated that some corals were already dying. 

Scientist Maya Srinivasan from the Tropical Water and Aquatic Ecosystem Research at the university said their surveys extending for multiple days at Keppel Islands popular among tourists found temperatures were significantly above average at 29 degrees Celsius. 

Srinivasan informed that during her work on the reefs spanning around 20 years, the water in the 27 sites surveyed across the island was the warmest. 

“Once we were in the water, we could instantly see parts of the reef that were completely white from severe bleaching. Some corals were already dying. Only the deeper areas of the reefs remained unimpacted,” she stated.

The scientist observed that climate change is the greater threat to the GBR and other coral reef ecosystems across the world’s oceans. The GBR stretches across 2,300 km and is made up of around 3,000 individual reefs.

The bleaching event is a scenario where the worst fears of scientists have come true as reefs in the past year have reported bleaching events in the Northern Hemisphere, resulting due to high sea surface temperatures owing to climate change and accelerated by El Nino conditions. 

AIMS senior research scientist Neal Cantin said bleaching of corals indicates a stress response which enables corals to recover, depending on the intensity of heat stress and its duration. However, he warned that prolonged or intense heat can prove fatal to corals.

The GBR has shown its resilience and ability to recover from past coral bleaching events and other extreme weather events such as severe tropical cyclones and crown-of-thorns starfish outbreaks, Beeden said.

Mass coral bleaching events have been witnessed in the past, starting from 1998 and then reported in 2002, 2016, 2017, 2020, 2022 and the latest in 2024. 

The current coral bleaching event marks the fifth event in the past eight years. 

Cantin said there is a need to combine spatial coverage recorded from the aerial survey with in-water surveys to calculate the severity and actual impact of coral bleaching in deeper areas of the reef habitats located in different regions of the Marine Park.

According to National Oceanic and Atmospheric Administration (NOAA) Satellite and Information Service, the third global coral bleaching event between 2014 and 2017 remains the longest, most widespread and probably the most damaging coral bleaching event on record. 

The three-year-long coral bleaching event affected reefs in areas such as GBR, Kiribati, Jarvis Island and is considered worse than any global bleaching event.

At present, the Coral Reef Watch programme has warned that the Earth is on the brink of experiencing a fourth global mass coral bleaching event, with reefs located in the Indian, Pacific and Atlantic oceans showing severe signs of bleaching. 

High ocean temperatures around the world have persisted over the past 12 months and may trigger the vulnerable ecosystem into mass coral bleaching. 

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