The marine heat waves that occurred last year were unprecedented, resulting in the creation of three new alert levels for coral reef bleaching by researchers.

The marine heat waves that occurred last year were unprecedented, resulting in the creation of three new alert levels for coral reef bleaching by researchers.

Some regions of the globe experienced extreme heat in the previous year, resulting in ocean temperatures reaching levels similar to those found in hot tubs. This led to the death of crucial coral reefs, an event that had never been seen before. In response, scientists were forced to update a coral bleaching warning system with three additional levels in order to safeguard marine organisms.

The Coral Reef Watch program, run by the National Oceanic and Atmospheric Administration, has updated its bleaching alert system due to the unusual marine heatwaves in 2023.

“The updated system offers more specific information to aid coral reef managers in preparing for and responding to periods of extreme heat stress,” stated the program on its social media platform.

Coral bleaching happens when coral animals are placed under excessive stress due to variations in temperature, light, or nutrients. As a result, the corals expel the algae living within their tissues, causing them to turn white, or, as stated by NOAA, become “bleached and at risk.” Bleached corals are not immediately fatal, but they depend on algae for nourishment, so their chances of survival decrease when the algae depart.

The current system categorizes the risk of coral bleaching on a scale of one to five, with one indicating a potential for reef-wide bleaching and five indicating a high likelihood of near complete mortality. A recent satellite image of heat stress alerts revealed that many areas worldwide are currently under coral bleaching watches, with some areas at levels one and two and at least one area in the Pacific Ocean at levels four and five.


The picture demonstrates the worldwide levels of coral reef alerts, exposing some regions with minimal bleaching and others with widespread occurrences.

NOAA Coral reef Watch

NOAA’s Coral Program shared on social media that there is a significant increase in heat stress in the southern hemisphere. They also noted that coral bleaching is likely to occur in various regions, such as the Indian Ocean, central equatorial and southwestern Pacific, including the Great Barrier Reef, over the coming months.

The continuation of El Niño

NOAA stated in their January update that the weather pattern known as will definitely have an impact. According to them, this phenomenon is currently at its peak strength and is expected to persist for the next few months. While it will gradually decrease in intensity, NOAA also mentioned that its effects on the global climate will persist.

El Niño typically creates warmer sea surface temperatures in the Pacific Ocean. Those temperatures usually peak between December and January. In December, NOAA found that the sea surface temperature in a key monitoring region in the Pacific was 2.1 degrees Celsius above the 1991-2020 average for that area.

the coral reefs in the Florida Keys experienced bleaching for 21 consecutive weeks.

The updated bleaching warning system was implemented in response to 2023 being declared the hottest year on record. The Florida Keys witnessed 21 weeks of continuous coral reef bleaching last summer due to high temperatures.

Some areas along the coast of Florida experienced ocean temperatures higher than 100 degrees Fahrenheit.

The temperatures in July were high enough to rival those of hot tubs, causing concern for a coral reef restoration site located off the coast. Researchers described the situation as “unimaginable.”100% coral mortality.” 

According to the Coral Restoration Foundation, the colorful coral reefs in Florida play a vital role in the community and economy, but they are currently in a dire situation due to high water temperatures. The Foundation warns that there is a high risk of losing these coral populations in the Florida Keys National Marine Sanctuary.