NOAA has confirmed the fourth global coral bleaching event. The first documented global bleaching event was in 1998, the second in 2010, the third from 2014 to 2017 and the present ongoing event from 2023 to 2025. The ongoing event is the largest on record, impacting 83.7% of the world’s coral reef area.
In a press release NOAA reported that since early 2023, mass bleaching of coral reefs has been confirmed throughout the tropics, including in Florida in the U.S.; the Caribbean; Brazil; the eastern Tropical Pacific (including Mexico, El Salvador, Costa Rica, Panama and Colombia); Australia’s Great Barrier Reef; large areas of the South Pacific (including Fiji, Vanuatu, Tuvalu, Kiribati, the Samoas and French Polynesia); the Red Sea (including the Gulf of Aqaba); the Persian Gulf; and the Gulf of Aden.
NOAA has received confirmation of widespread bleaching across other parts of the Indian Ocean basin as well, including in Tanzania, Kenya, Mauritius, the Seychelles, Tromelin, Mayotte and off the western coast of Indonesia.
“As the world’s oceans continue to warm, coral bleaching is becoming more frequent and severe,” said Derek Manzello, Ph.D., NOAA CRW Coordinator. “When these events are sufficiently severe or prolonged, they can cause coral mortality, which hurts the people who depend on the coral reefs for their livelihoods.”
Coral bleaching occurs when corals expel their zooxanthellae due to environmental stress, such as high temperatures or pollutants. When zooxanthellae, who give coral their bright colors, are expelled, corals appear white and die. Dead corals will erode, depleting the rich, highly diverse ecosystems they support.
Coral reefs provide shelter, breeding grounds, and nursery habitat for many ocean inhabitants. Coral reefs have one of the highest levels of biodiversity (the total number of species in an area) on the planet.
Coral bleaching, especially on a widespread scale, impacts economies, livelihoods, food security and more, but it does not necessarily mean corals will die. If the stress driving the bleaching diminishes, corals can recover and reefs can continue to provide the ecosystem services we all rely on.
Photo courtesy of NOAA