the Editor says: Did you know that coral bleaching does not actually equal coral death? However, when the condition persists, corals will begin to die off one by one. This past March, Australia's Great Barrier Reef was also confirmed to be undergoing its fifth mass bleaching event, with over half of the world's coral reefs now in crisis. <Full article reprinted from: Environmental Information Center; translated by 吳凱西; reviewed by 陳文姿 and 林大利>
Ocean temperatures are sounding the alarm, with bleaching disasters being reported around the world. The U.S. National Oceanic and Atmospheric Administration (NOAA) announced on the 15th that the world is experiencing its fourth mass coral bleaching event — also the second such event in the past decade.
Coral bleaching at Martin Reef in the northern Great Barrier Reef, Australia, in March 2024. Photo: Veronique Mocellin. Image source: Australian Institute of Marine Science
Coral Bleaching Crisis Spreads Globally — Over Half of Reefs Threatened
According to Reuters, rising ocean surface temperatures driven by global warming have prompted NOAA to report that, from February 2023 to the present, coral bleaching has been confirmed in more than 54 countries and territories worldwide.
NOAA has long used satellite monitoring of global sea surface temperatures, along with in-situ measurements and modelling tools, to provide a coral bleaching alert system. According to NOAA, over the past 365 days, coral bleaching has spread across the Atlantic, Pacific, and Indian Oceans.
Derek Manzello, coordinator of NOAA's Coral Reef Watch programme, stated that more than 54% of the world's coral reefs are currently enduring heat stress severe enough to trigger bleaching.
Coral bleaching is a physiological stress response in the coral-algae partnership (collectively known as the coral holobiont) and does not equate to coral death. However, when the stress is sustained — such as prolonged exposure to high temperatures and intense light — and the holobiont exceeds its physiological limits, corals will begin to die.
Marine scientists are deeply worried, and even outraged, by the severity of the coral bleaching. BBC noted that the first warning sign came from the Caribbean, when swimmers off the coast of Florida in the United States noticed unusually warm waters last year (2023). The Southern Hemisphere then also experienced marine heatwaves, affecting the Great Barrier Reef in Australia, Tanzania, Mauritius, Brazil, Pacific Island nations, and areas including the Red Sea and the Persian Gulf.
NOAA's Coral Reef Watch showing coral bleaching alert levels from 1 January 2023 to 10 April 2024. (Image source: NOAA)
Australia's Great Barrier Reef Undergoes Fifth Mass Bleaching Event
Australia in the Southern Hemisphere entered summer at the end of last year, and ocean temperatures have continued to rise. The Great Barrier Reef Marine Park Authority (GBRMPA) confirmed in March that the Great Barrier Reef is experiencing a mass bleaching event — the fifth bleaching crisis in eight years. Aerial survey results showed severe coral bleaching in shallow-water areas, and underwater surveys are being conducted to confirm the severity and extent of the bleaching.
The Australian Marine Conservation Society stated in April that aerial surveys indicate coral bleaching has now affected 75% of the Great Barrier Reef.
"I feel devastated," said Selina Ward, former academic director of the Heron Island Research Station at the University of Queensland and a coral reef expert who surveyed 16 sites in the southern Great Barrier Reef. She said it was the worst she had seen in her 30 years of work.
The GBRMPA further confirmed on the 17th that the bleaching is extremely widespread, with nearly 46% of the Great Barrier Reef's corals exposed to record-level heat stress. Approximately 60% of corals may have bleached due to significant heat stress exposure; detailed underwater surveys are still ongoing, and more time is needed to understand the full extent of the impact.
According to The Guardian, Terry Hughes, emeritus professor at James Cook University in Australia and a leading coral bleaching expert, noted that every coral reef ecosystem has experienced coral bleaching since 1998, with some locations having bleached three to four times. This cumulative impact gradually weakens the resilience of coral reefs over time.
Results of the Great Barrier Reef Marine Park Authority's (GBRMPA) 2024 aerial survey observations of bleaching rates on shallow-water coral reef communities of the Great Barrier Reef. Image source: Great Barrier Reef Marine Park Authority (GBRMPA)
References
- BBC (15 April 2024), Coral bleaching: Fourth global mass stress episode underway - US scientists
- NOAA (15 April 2024), NOAA confirms 4th global coral bleaching event
- AP (15 April 2024), Scientists say coral reefs around the world are experiencing mass bleaching in warming oceans
- Great Barrier Reef Marine Park Authority (17 April 2024), REEF HEALTH UPDATES
- Australian Marine Conservation Society (11 April 2024), 'Worst I've seen': new footage shows Reef bleaching in deeper waters from record marine heatwave
- The Guardian (11 April 2024), Great Barrier Reef suffering 'most severe' coral bleaching on record as footage shows damage 18 metres down
Related Links
- Environmental Information Center official website
- Original article: NOAA Confirms Fourth Global Mass Coral Bleaching Event — Over Half of the World's Coral Reefs in Crisis
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