by A sudden marine heat wave off the coast of Florida has surprised scientists and sent water temperatures to unprecedented heights, threatening one of the most severe coral bleachings the state has ever seen.
Sea surface temperatures around Florida have reached the highest levels on record since satellites began collecting ocean data. And the warming is occurring much earlier than usual – yet another example of ocean warmth being amplified by the man-made climate crisis and the extreme weather it brings.
“We didn’t expect this warming to happen so early in the year and to be so extreme,” Derek Manzello, coordinator at Coral Reef Watch of the National Oceanic and Atmospheric Administration, told CNN. “This seems unprecedented in our records.”
The exceptional temperatures—nearly 97 degrees Fahrenheit in some areas—are more than just another alarming climate record; extreme ocean heat and its duration are critical in determining the survival of coral reefs. Temperatures that are too high for too long cause coral to fade and turn starkly white as they expel their algal food source and slowly starve to death.
Coral that bleaches doesn’t always die, but the more intense the heat and the longer it lasts, the more inevitable death becomes, coral experts said.
All it takes is a sea surface warming of 1 degree Celsius, or 2 to 3 degrees Fahrenheit, beyond the reef’s normal highest temperature to cause the heat stress that leads to bleaching, according to Manzello. Sea surface temperatures around Florida are more than 2 degrees Celsius above that normal range and have been for one to two weeks, he said.
Buoys off the coast of Florida measured hot tub-like water temperatures near 97 degrees Fahrenheit on Monday in Florida’s shallow, heat-prone bay between Florida’s southernmost tip and the Keys. The more ecologically vital and extensive coral reefs are to the east and south of the Florida Keys, but the buoy readings indicate just how extreme Florida’s heat has been so unusually early in the summer.
Ocean temperatures around Florida tend to get hotter as summer progresses and don’t peak until late August into September, Manzello said, meaning ocean temperatures could rise further.
That would mean “significant and severe” bleaching will begin within the next week and the coral could die completely within a month, he said.
“It remains to be seen whether this event will be more or less severe than previous events,” Manzello said. “However, all evidence at this point points to the fact that it will be one of the most serious events we have seen.”
Bleaching is already taking place in the Florida Keys, which is home to 6,000 individual reefs. Eleven partial bleaching observations were confirmed by the Mote Marine Laboratory in June. Experts said they expected this number to grow exponentially in the coming weeks.
An ‘existential crisis’ for coral
Katey Lesneski witnessed bleaching with her own eyes last weekend while diving an unnamed reef off the coast of Islamorada, one of the northern Florida Keys. Lesneki is the monitoring coordinator for Mission: Iconic Reefs, a NOAA project that aims to restore seven “iconic” reefs around the Florida Keys to their former glory over the next 20 years by planting and growing coral there.
She said she saw the initial stages of bleaching happening in coral up to 60 feet deep.
“The corals look much lighter in color. They’re usually pretty robust tones of yellow and green and brown and orange, but they’re literally starting to look like someone threw bleach on them,” Lesneski told CNN.
A NOAA study published last year found that climate change-induced coral disease
and bleaching had already eroded 70% of Florida’s coral reefs. The seven reefs Lesneski is trying to restore went from more than 50% coral cover to just 2% coral cover by the time her program started in 2019.
Florida is losing more than just the coral. Coral reefs generate billions of dollars for Florida’s economy through activities such as fishing and tourism, which would not be possible without reefs to protect the species that depend on them.
“Just from an ecological point of view, about 25% of marine species depend on coral reefs at some point in their lives,” Lesneski said. “That’s everything from the pretty fish that people like to look at to the big game fish…those fish are getting their start and rely heavily on other components of the reef at some point.”
Florida’s latest coral crisis is just one symptom of the broader threat of climate change, which could wipe out all of Earth’s coral reefs by 2100, a recent study finds.
“What we’re looking at now is another reduction in deaths by a thousand wounds,” Manzello said.
“Ocean warming is only getting worse, bleaching events are becoming more common, so it’s really an existential crisis for coral reefs as we know them.”
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