MIAMI — A sudden marine heat wave off the coast of Florida surprised scientists and raised water temperatures to unprecedented levels, threatening one of the most severe coral bleaching events ever seen in the state.
Sea surface temperatures around Florida have reached their highest levels on record since satellites began collecting ocean data. And warming is occurring much earlier than usual—another example of how ocean heat is being amplified by the human-caused climate crisis and resulting extreme weather.
“We didn’t expect warming to happen so early this year and be so extreme,” Derek Manzello, coordinator for the National Oceanic and Atmospheric Administration’s Office of Coral Reef Watch, told CNN. “It seems unprecedented in our records.”
The exceptional temperatures – around 97 degrees Fahrenheit in some areas – are more than just another troubling climate record; extreme ocean heat and its duration are critical to the survival of coral reefs. Too much heat for too long causes corals to bleach, turning them ghostly white as they expel their algae food source and slowly starve to death.
Corals that bleach don’t always die, but the stronger the heat and the longer it lasts, the more inevitable death becomes, coral experts say.
According to Manzello, all it takes is a warming of the sea surface by 1 degree Celsius, or 2 to 3 degrees Fahrenheit, above the reef’s normal maximum temperature to induce heat stress, which leads to bleaching. Sea surface temperatures around Florida are more than 2 degrees Celsius above the normal range for one to two weeks, he said.
Buoys off the coast of Florida measured a hot-tub-like temperature of about 97 degrees Fahrenheit on Monday in the shallow, heat-prone Florida Bay between the southern tip of Florida and the Keys. More ecologically important and extensive coral reefs are located east and south of the Florida Keys, but buoy measurements show how extreme hot Florida was unusually early in the summer.
Ocean temperatures around Florida typically get warmer as the summer progresses and don’t peak until late August through September, Manzello said, meaning ocean temperatures could rise even more..
That would mean “significant and severe” bleaching would begin next week, and corals could begin to die completely within a month, he said.
“It remains to be seen if this event will be more or less severe than previous events,” Manzello said. “However, all the evidence right now points to the fact that this will be one of the most serious events we have seen.”
The bleaching is already happening in the Florida Keys, where there are 6,000 individual reefs. Mote Marine Laboratory confirmed eleven cases of partial discoloration in June. Experts said they expect the number to grow exponentially in the coming weeks.
“Existential crisis” for corals
Kathy Lesnesky saw the whitening firsthand last weekend while diving off an unnamed reef off the coast of Islamorada, one of the northern Florida Keys. Lesnecki is 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 corals there.
She said she saw the initial stages of coral bleaching at depths of up to 60 feet.
“The corals look a lot lighter, usually pretty bright shades of yellow, green, brown and orange, but they literally start to look like someone has doused them with bleach,” Lesnesky told CNN.
NOAA Study Published Last year, it was found that coral disease and bleaching caused by climate change had already destroyed 70% of Florida’s coral reefs. The seven reefs Lesnesky is trying to restore have grown from over 50% coral coverage to just 2% coral coverage by the time her program launches in 2019.
Florida is losing more than just coral. Coral reefs bring billions of dollars to the Florida economy through activities such as fishing and tourism that would not be possible without reefs to protect the species that rely on them.
“From an ecological point of view, about 25% of marine species depend on coral reefs at some point in their lives,” Lesnesky said. “It’s everything from the beautiful fish that people love to look at to the big game fish…these fish come into existence and at some point are highly dependent on other components of the reef.”
Florida’s latest coral crisis is yet another symptom of a broader climate change threat that could wipe out all of Earth’s coral reefs by 2100, a recent study found.
“What we’re looking at right now is another thousand cut death reduction,” Manzello said.
“Ocean warming is only getting worse, bleaching events are becoming more frequent, so this is really an existential crisis for coral reefs as we know them.”