New Method Predicts Coral Bleaching Five To Six Months In Advance

A new method is helping reef managers predict coral bleaching five to six months in advance, giving them time to put protections in place, according to a recent study (attached). Researchers found that since 1990, 10 of 11 coral bleaching events off the coast of Curaçao occurred when three large-scale Pacific and Atlantic climate modes aligned, offering insight into the factors that need to be present for coral bleaching to occur.

To build a long-term bleaching record, the research team analyzed skeletal cores from massive reef-building corals collected from Curaçao’s reefs. Using CT scans of 44 coral cores, the researchers reconstructed a 72-year bleaching history from 1950 to 2022, revealing that significant bleaching events on Curaçao began only around 1990, after ocean temperatures had already warmed significantly.

The study found that bleaching has occurred repeatedly in years when three large-scale climate modes align: Atlantic Multidecadal Variability, El Niño–Southern Oscillation, and North Atlantic Oscillation. When these patterns combine in certain ways, they weaken regional winds and reduce cooling induced by upwelling currents, allowing reef temperatures to rise above bleaching thresholds.

Although the Bleaching Event Early Predictor was developed for Curaçao, researchers say the framework is likely adaptable across reef systems. This could help reef managers in places like the Florida Reef, which sits within Biscayne and Dry Tortugas national parks, put reef protections in place ahead of predicted bleaching events.

Coral reefs in national parks in Hawai’i have also been hit hard by coral bleaching. A recent study found that between the early 2000s and 2022, live coral cover declined across three parks. On the Florida Reef, staghorn and elkhorn corals are considered functionally extinct after dwindling in the face of repeated marine heatwaves and coral bleaching.

“Existing bleaching forecasts track heat stress in near-real time, and also rely on generalized thresholds for predicting bleaching risk, which means they often do not provide reef managers and restoration practitioners with enough lead time to prepare and respond effectively, or the predictions are inaccurate,” explained Mariya Galochkina, lead author of the study. “We take a different approach by using large-scale climate patterns that interact to shape regional ocean and atmosphere conditions with a time lag, which lets us identify bleaching risk months in advance.”

With advanced warning, reef managers can move coral fragments from in-situ restoration nurseries to cooler areas on the reef or out of the water and into land-based nurseries if bleaching is forecast.

“Coral reefs are among the most vulnerable ecosystems on the planet,” said Anne Cohen, senior scientist at WHOI and co-author of the study. “Advances like this give us a better chance to protect them in a warming ocean.”