A sudden marine heat wave off the coast of Florida has surprised scientists and sent water temperatures soaring to unprecedented levels, threatening one of the most severe coral bleaching events 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 happening much earlier than normal – another example of ocean heat amplified by the human-caused climate crisis and the extreme weather it brings.
“We didn’t expect this warming to happen so early in the year and be so extreme,” Derek Manzello, coordinator of the National Oceanic and Atmospheric Administration’s Coral Reef Watch, told CNN. “This appears to be unprecedented in our records.”
The exceptional temperatures – close to 97 degrees Fahrenheit in some areas – are more than just another alarming climate record; extreme ocean heat and its duration are critical to deciding the survival of coral reefs. Temperatures that are too hot for too long cause the corals to bleach, turning a hideous white as they expel their algal food source and slowly starve.
Bleaching corals won’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 sea surface warming of 1 degree Celsius, or 2 to 3 degrees Fahrenheit, beyond the reef’s highest normal temperature to trigger the heat stress that leads to bleaching, according to Manzello. Sea surface temperatures around Florida are more than 2 degrees Celsius above the normal range and have been for one to two weeks, he said.
Buoys off the coast of Florida measured water temperatures similar to a hot tub close to 97 degrees Fahrenheit Monday in the shallow, heat-prone Florida Gulf between the southern tip of Florida and the Keys. More ecologically important and more extensive coral reefs are located to the east and south of the Florida Keys, but buoy measurements indicate how extreme the heat in Florida has been for such an unusually early summer.
Ocean temperatures around Florida typically get warmer as the summer progresses and don’t peak until late August into September, Manzello said, meaning ocean temperatures could rise even more..
That would mean “significant and severe” bleaching would begin in the next week and corals could begin to 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 the evidence at this point is that it will be one of the worst events we’ve seen.”
Bleaching is already occurring in the Florida Keys, home to 6,000 individual reefs. Eleven observations of partial bleaching were confirmed by Mote Marine Laboratory in June. Experts said they expected that number to grow exponentially in the coming weeks.
Katey Lesneski saw the bleaching firsthand last weekend while diving an unnamed reef off the coast of Islamorada, one of Florida’s North Keys. Lesneki is the monitoring coordinator for Mission: Iconic Reefsa NOAA project that aims to restore seven “iconic” reefs around the Florida Keys to some of their former glory over the next 20 years by planting and growing corals there.
She said she has seen the early stages of bleaching occur in corals up to 60 feet deep.
“The corals look a lot lighter in color, they’re usually pretty robust yellows and greens and browns and oranges, but they’re starting to look like someone threw bleach on them,” Lesneski told CNN.
A published NOAA study last year found that climate change-fueled coral disease and bleaching had already eroded 70% of Florida’s coral reefs. The seven reefs Lesneski is trying to restore have gone from more than 50 percent coral coverto just 2% coral cover by the time her program launches in 2019.
Florida is losing more than coral. Coral reef 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 rely on them.
“From an ecological standpoint alone, about 25 percent of marine species depend on coral reefs at some point in their lives,” Lesneski said. “That’s everything from the cute fish that people like to look at to the big game fish…those fish start and are very dependent on other components of the reef at any given time.”
Florida’s latest coral crisis is just another symptom of the broader threat of climate change, which could destroy all the Earth’s coral reefs by 2100found a recent study.
“What we’re looking at now is another reduction in a death by a thousand cuts,” Manzello said.
“Ocean warming is only getting worse, bleaching events are becoming more frequent, so it really is an existential crisis for coral reefs as we know them.”