Record-high Water Temperatures Cause Early Bleaching of Florida Keys Coral Reefs, Warn Scientists

by Lucas Garcia
Coral Bleaching

This summer, several coral reefs in the Florida Keys are experiencing discoloration earlier than expected due to unprecedented water temperatures, indicating potential health hazards and stress, according to federal scientists.

Katey Lesneski, Research and Monitoring Coordinator for Mission: Iconic Reefs—a program by the National Oceanic and Atmospheric Administration (NOAA) aimed at preserving Florida’s coral reefs—states that the corals, which should be in full color this season, are rapidly turning white.

“Signs of bleaching are already noticeable as corals appear to be losing their color and turning stark white. And we still have more to witness,” Lesneski, who has spent considerable time on the reefs in the past fortnight, revealed.

NOAA scientists have recently escalated their coral bleaching warning to Alert Level 2—the highest heat stress level— which is reached when the average water surface temperature exceeds the usual maximum by approximately 1.8 degrees Fahrenheit (1 degree Celsius) for a continuous eight-week period.

Jacqueline De La Cour, Operations Manager for NOAA’s Coral Reef Watch program, stated that the surface temperatures around the Keys have averaged about 91 degrees (33 Celsius), significantly higher than the typical mid-July average of 85 degrees (29.5 Celsius). Prior Alert Level 2s were observed in August, she added.

Corals, formed by numerous tiny organisms that connect together, derive their color from the algae they house and depend on for nourishment. Excessive temperatures cause the coral to expel this algae, rendering the reefs white or bleached. While this does not equate to the death of the coral, it leaves them vulnerable to starvation and disease.

Initial signs of bleaching were detected on some coral reefs as early as two weeks ago, reports Andrew Bruckner, Research Coordinator at the Florida Keys National Marine Sanctuary. In recent days, some reefs have entirely lost their color—a phenomenon previously unrecorded before August 1st. Traditionally, bleaching peaks around late August or September.

“The process is running at least one to two months ahead of schedule,” Bruckner noted. “While we haven’t witnessed any mortality from bleaching yet and only a minor number of corals have turned completely white, the early signs are concerning.”

Forecasting the remainder of the summer remains challenging, De La Cour and Bruckner expressed. Although a further increase in water temperatures could be disastrous, potential tropical storms or hurricanes could stir up the water and cool it down. Additionally, the arrival of dusty air from the Sahara Desert over Florida could temper the sun’s rays and reduce temperatures.

Climate change and other factors have resulted in an 80% to 90% loss of coral in the Keys waters over the past half-century, according to Bruckner. This not only impacts marine life relying on the reefs but also human populations. Coral reefs serve as a natural barrier against storm surges, and tourism-based activities such as fishing, diving, and snorkeling depend heavily on these reefs.

Efforts to restore Florida’s coral to about 90% of its state 50 years ago have begun as part of a large-scale, 20-year project. The scientists are exploring breeding heat-resistant corals and implementing measures like shade covers and underwater fans to keep the waters cool and promote their survival.

Jason Spadaro, Coral Reef Restoration Program Manager for Mote Marine Laboratory & Aquarium, emphasized the importance of breeding corals for developing heat resistance in future generations.

It’s noted that the extent of coral bleaching is more severe in the lower Keys compared to the northern parts. The Keys have had bad bleaching years before, but this year, the situation is “extremely severe and persistent,” Spadaro stated.

Ross Cunning, a Research Biologist at Shedd Aquarium in Chicago, echoes the concern, pointing out that the unusually high water temperatures could lead to a catastrophic bleaching event.

De La Cour emphasizes the critical role of addressing human-induced global warming for the survival of corals.

“If we fail to decrease our greenhouse gas emissions and don’t address the gases already in our atmosphere, we are paving the way towards a world where coral reefs cannot thrive, regardless of our efforts,” she concluded.

Reporting by Whittle from Portland, Maine.

Several private foundations support Big Big News’ climate and environmental coverage. More about AP’s climate initiative can be found here. AP is solely accountable for all content.

Frequently Asked Questions (FAQs) about Coral Bleaching

Why are the coral reefs in the Florida Keys bleaching early?

The coral reefs in the Florida Keys are bleaching earlier than usual this year due to record-high water temperatures. This increased heat causes the corals to expel the algae they house, causing them to appear white or bleached.

What are the potential consequences of early coral bleaching?

Early coral bleaching can lead to starvation and disease in corals, as they lose the algae they rely on for nourishment. If the high water temperatures persist, it could potentially lead to a catastrophic bleaching event.

What is being done to help the bleached coral reefs in the Florida Keys?

Scientists are undertaking a large-scale effort to restore the Florida coral reefs to their state 50 years ago. This includes breeding heat-resistant corals and using shade covers and underwater fans to cool the waters.

What role does climate change play in coral bleaching?

Climate change contributes to the increase in water temperatures which causes coral bleaching. Over the past 50 years, climate change and other factors have led to an 80% to 90% loss of coral in the Florida Keys.

How does coral bleaching affect local economies and ecosystems?

Coral reefs serve as a natural barrier against storm surges and support diverse marine life. Furthermore, local economies heavily depend on these reefs for tourism-based activities such as fishing, diving, and snorkeling.

More about Coral Bleaching

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LizzyB July 22, 2023 - 3:56 am

this is so distressing to read. Those poor corals! I wish there was more i could do to help.

MarineBioGeek July 22, 2023 - 4:19 am

Thanks for reporting on this. It’s important that more people know what’s happening to our marine ecosystems. There’s still hope, though! Science will find a way.

SammyJoe July 22, 2023 - 8:48 pm

Wow, this is crazy!! Isn’t there some way to cool down the water or something? It’s really bad that the corals are suffering because of us.

EcoWarrior July 23, 2023 - 1:27 am

Climate change is real, people! Look what we’re doing to our oceans! it’s high time we took some serious action, like yesterday.


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