MIAMI – A worldwide coral bleaching event is ongoing, marking the fourth-ever global coral bleaching on record and the second in a decade, according to NOAA scientists.
NOAA’s Coral Reef Watch (CRW) has been monitoring sea surface temperatures since the 1980s, looking for warmer-than-average temperatures that can cause heat stress to corals. NOAA said CRW predicted the current coral bleaching event unfolding worldwide.
AFTER ‘FIRST OF ITS KIND’ HEAT WAVE, FLORIDA CORALS BEGIN RETURN TO OCEAN
Depending on the type of coral, 2-3 degrees above average temperatures is all it takes for heat stress to begin to take its toll.
Coral animals rely on single-celled algae, which produce food for corals through photosynthesis. The algae are how corals get their color. When temperatures get too hot, instead of photosynthesis, the algae produce toxins that create free radicals. Coral biologists call this oxidative stress, which turns the algae “helpers” into killers.
In Florida, thermal stress on coral begins when sea surface temperatures reach 88-89 degrees. Florida sea surface temperatures exceeded those levels with an unprecedented spike into the high 90s in June 2023.
The heatwave in Florida remains unprecedented because of weeks of extreme temperatures and how early the bleaching event began.
During previous large-scale bleaching events in the Florida Keys in 2014 and 2015, bleaching-level sea surface temperatures did not happen until mid-August. Last year, bleaching levels were being measured by NOAA buoys in early June.
NOAA scientists said warming ocean temperatures mean more coral bleaching events are likely.
“Climate model predictions for coral reefs have been suggesting for years that bleaching impacts would increase in frequency and magnitude as the ocean warms,” said Jennifer Koss, NOAA’s Coral Reef Conservation Program director.
LESS THAN 22% OF STAGHORN CORAL IN FLORIDA SURVIVED MARINE HEAT WAVE, SCIENTISTS SAY
NOAA CRW coordinator Derek Manzello said significant coral bleaching was documented in the oceans in both the Northern and Southern hemispheres between February 2023 and April 2024.
In July, Manzello told FOX Weather the agency had been closely watching sea surface temperatures since March 2023 because of an El Niño that was developing. Warm water during El Niño years is historically tied to large coral bleaching events.
When bleaching began in the tropics last year, the Key Marine Laboratory kept thousands of corals safe in onshore tanks until temperatures were safe to begin returning the corals to the ocean.
Officials said the global event requires world action under the International Coral Reef Initiative, which NOAA co-chairs.
NOAA coral scientists learned a “great deal” while trying to mitigate the harm to corals in Florida and the Caribbean as part of the Coral Reef Initiative. NOAA said they continue to apply new techniques and what they learned to the ongoing coral bleaching event.