Evidence mounts that Florida’s corals are devastated by warm ocean waters this summer

By nearly all metrics, the marine heat wave striking Florida has caused the worst coral bleaching event in the state’s history: The heat arrived sooner. The water is running hotter. It’s staying hotter longer.

Many of the corals off the Florida Keys have already been sitting in dangerously high ocean temperatures for six weeks, and evidence of the damage is mounting.

Take, for instance, Cheeca Rocks, a historically resilient patch reef off the coast of Islamorada. There, corals have suffered nearly 50 days of temperatures higher than 90 degrees Fahrenheit.

At that temperature, for that long, corals begin to spit out the tiny algae species living in their tissue, sucking the color from their bodies. Bleaching not only makes corals more susceptible to disease — it also can hinder their future reproduction for years. If they survive the heat at all.

In less than one month’s time, all the hard coral species at Cheeca Rocks have bleached or paled, and soft corals like sea fans have completely disintegrated.

“This is not what a reef is supposed to look like,” said Ian Enochs, a research ecologist at the federal Atlantic Oceanographic and Meteorological Laboratory.

Enochs joined several other coral experts with the National Oceanic and Atmospheric Administration for an update Thursday on the bleaching crisis not only threatening Florida but most of the Caribbean now, too. The upshot: Experts who have spent decades studying these crucial marine ecosystems are “truly sobered” by what’s happening.

Images shared by scientists showed bleak white coral heads that were bustling with color just months ago.

To make matters worse, the superheated ocean temperatures likely aren’t going away anytime soon. Assuming no hurricanes blast through the Keys and bring a cruelly ironic relief with cooler water, corals could see at least another month of bleaching-level heat stress, according to Derek Manzello, the coordinator of the National Oceanic and Atmospheric Administration’s Coral Reef Watch Program.

“We hear the word ‘unprecedented’ thrown around all the time, but allow me to qualify that word with the facts: This event is unprecedented because Florida’s corals have never been exposed to this magnitude of heat stress, and this heat occurred earlier than ever before,” Manzello said.

A big concern, Manzello said, is that temperatures are just reaching their seasonal peak right now, more than a month after harmful heat stress began. In the past eight mass bleaching events to strike the Florida Keys since 1987, bleaching didn’t occur until roughly mid-August of each year. But this year is different: The heat has caused corals to bleach six weeks earlier.

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“These corals will experience heat stress that is not only higher than ever before, earlier than ever before — but for longer than ever before,” Manzello said.

Record-high ocean temperatures

As of Thursday, ocean surface temperatures in the Keys had been higher than the previous summer-high record of 89.6 degrees Fahrenheit for 28 of the past 37 days. The record was broken on July 9, according to Manzello.

Florida is the location most impacted by the ongoing marine heat wave, ocean scientists say, but it’s not the only place experiencing a bleaching crisis. Thousands of miles, spanning seven countries or territories in the Atlantic, also have confirmed bleaching, including Mexico, Panama and Cuba.

Effects from climate change, exacerbated by a lingering El Niño and other meteorological factors, are driving the increased heat not only in Florida but across the globe, according to Manzello.

Florida was the only state in the contiguous United States to see record average temperatures over a six-month period between January and July of this year, according to data provided by federal ocean scientists. That’s based on 129 years of temperature records dating back to 1895.

Heat stress hasn’t been uniform everywhere in the Keys, and experts are observing the most severe impacts in the middle and lower Keys, where the heat began to rear its head in June.

While it’s hard for experts to pin down a specific percentage, coral experts are seeing signs of coral bleaching “pretty much everywhere” throughout the Florida Keys National Marine Sanctuary system, which stretches 180 miles from south Miami to the Dry Tortugas, according to Andy Bruckner, a research coordinator for the sanctuary.

The sanctuary is home to more than 6,000 species of marine life and contains North America’s only barrier coral reef. It’s not just marine life that depends on the reef: The reef system provides thousands of jobs and draws in an estimated $1.1 billion annually in tourism dollars. It’s also a barrier to rising seas and storm surge.

“I am truly sobered by the impacts of the current marine heat wave on Florida’s reefs,” said Steven Thur, the National Oceanic and Atmospheric Administration’s assistant administrator for oceanic and atmospheric research.

The ongoing bleaching crisis underscores the importance of sweeping restoration projects, like the $100 million Mission: Iconic Reefs, a collaboration to restore nearly 3 million square feet of the Florida Reef Tract at seven reef sites, Bruckner said. Still, experts agree these restoration efforts have to happen at the same time as a large-scale curbing of greenhouse gas emissions from fossil fuels.

A spokesperson for the Florida Department of Environmental Protection said last week the state had devoted more than $50 million since 2019 for coral reef recovery and restoration — but stopped short of connecting supercharged temperatures to climate change. An email to a spokesperson for Florida Gov. Ron DeSantis seeking past or present comments from the governor about the environmental crisis went unanswered.

“Coral reefs in Florida and around the world are vitally important to human and natural communities,” Thur said. “They’re also on the front line of climate change impacts.”