Why Florida scientists have a hint of hope amid coral bleaching crisis
Coral spawning just brought a wave of much-needed excitement to coral scientists working to curb the bleaching crisis.
Deep in the throes of the most severe coral bleaching event in Florida’s history, Keri O’Neil, a coral scientist by trade, was in need of some hope.
It was two weeks since her team joined the scramble to rescue corals from superheated ocean waters off the Florida Keys. The whirlwind few days of travel left O’Neil and many scientists feeling deflated, and hope was hard to come by.
But at exactly 2:25 p.m. Friday, after scientists had checked in on the saltwater tanks in their pitch-dark lab every seven minutes for the past hour, hope finally arrived.
At that minute, excitement replaced exhaustion. Coral babies were on the way.
An exhilarating “It’s happening!” rang through the lab when an elkhorn coral started to spit out teeny spheres, one by one. These are commonly called “bundles,” a combo of sperm and egg that meander like bubbles in a lava lamp to the surface.
Bundles are precious to O’Neil and her team at the Florida Aquarium, who eagerly scooped them from the tank and placed them in containers. Bundles are smaller than a millimeter across, but if handled properly, they could soon be the next generation of corals that may, one day, be planted at sea.
The buildup and release of these bundles, called “spawning,” is hard to accomplish in a lab. But when it happens, it’s a big milestone in the fight to increase the genetic diversity of an animal in desperate need of saving.
It’s tough work getting corals to successfully spawn in an environment outside of the ocean. For one: It only happens once a year, and the lab’s conditions must mimic the ocean at night to kick off the spawning process. Corals typically spawn during the first full moon in early August, which means scientists have to perfect the lighting so it resembles a sunset.
Another complicating factor? Different coral species may not spawn on the same day, and some eggs take up to 10 months to form. It has taken researchers decades of careful observation to learn their different behaviors, their likes and dislikes.
Add an unprecedented, ongoing severe marine heat wave that threatens the existence of one of the most complex creatures on Earth, and the miraculous significance of this year’s coral spawning starts coming into view.
“It’s been an emotional roller coaster. I’m running on lots of caffeine and adrenaline still, but we have to keep the hope,” said O’Neil, director of the Florida Aquarium’s Coral Conservation Program.
“These spawning events captivate me every time it happens. Every single time I get just as excited and just as silly and happy,” O’Neil said. “There’s still hope.”
Coral successes put to the ultimate test
The Florida Aquarium team will now separate the eggs and sperm and pair them with the releases from other corals, usually from a reef dozens of miles away, to improve genetic diversity.
It wasn’t just O’Neil’s lab in Apollo Beach that has successfully spawned corals in recent days — despite the risk to restoration posed by the hottest ocean temperatures ever documented in the Keys region.
Several rescued corals plucked from Miami’s hot waters spawned in the University of Miami’s Rosenstiel hatchery lab last week. At a lab farther south, staghorn corals evacuated by the Coral Restoration Foundation spawned at Keys Marine Laboratory on Long Key late Friday night.
And offshore in ocean waters, marine biologists from the university also filmed threatened staghorn corals spawning off Key Largo, despite many of them being bleached or dying.
“So poignant to see these incredibly stressed corals still helping the population continue,” wrote Liv Williamson, the assistant scientist of marine biology and ecology at the University of Miami who filmed and shared footage of the offshore spawning last week.
When temperatures rise, corals bleach, or weaken, as they oust the tiny algae species in their tissues. As global climate change worsens from human-released greenhouse gas emissions, corals are only becoming more vulnerable.
Some entire sections of reef, like Cheeca Rocks within the Florida Keys National Marine Sanctuary, are now nearly or entirely bleached.
“We keep seeing the reefs get hit — over and over and over again,” said Jennifer Moore, the threatened coral recovery coordinator for the National Oceanic and Atmospheric Administration. “But the whole point of this reproduction is so that we can create new corals that we can put out on the reefs.”
Moore has worked with corals for two decades, she said, but it wasn’t until recently that organizations such as the Florida Aquarium began successfully spawning corals in a laboratory setting.
In 2019, the aquarium spawned several species of Atlantic coral for the first time. And more recently, in 2022, O’Neil and other scientists successfully reproduced elkhorn coral for the first time in history. Those victories are now being put to the test like never before.
“It’s really hard because we put so much blood, sweat and tears into restoration activities,” said Moore, who was visiting the Apollo Beach lab Friday.
“But I have hope — because we’re all doing stuff.”
“We absolutely have to deal with the primary threats.”
Waters offshore of the Florida Keys first crossed a crucial boundary, called the “bleaching threshold,” on June 14, according to data provided by federal ocean scientists. Water temperatures have remained above that line since.
The first signs of trouble emerged in mid-July when heat-stressed corals in the southern Florida Keys began showing signs of bleaching. Bleaching starts when temperatures reach about 2 degrees Fahrenheit above the usual summer peak.
The stress first shows itself when corals become patchy-looking. Even a few more days in scorching temperatures after that, and corals turn stark white. It’s the ultimate signal of distress.
Now, fast forward weeks later, with little relief from the heat, and scientists fear the possibility of a mass-mortality event as some reef sections are already entirely bleached. That’s why coral spawning in a lab is so crucial, Moore said.
As of Sunday, the entirety of the Florida Keys was under a bleaching Alert Level 2, the highest alert level on the scale. That threshold is reached when the average sea surface temperature runs above the normal maximum for eight weeks. Tampa Bay was also placed under a Level 2 last week.
During a bad summer, the number of weeks when the water temperature is above a coral’s bleaching threshold for a given location is usually eight to 10 weeks, according to Bill Precht, a Miami-based coral scientist.
If temperatures hold through August and September, corals could be looking at 14 weeks or more of extreme heat this year. The effects of climate change superimposed by an El Niño weather pattern are to blame for the crisis, Precht said.
While on the campaign trail for president, Gov. Ron DeSantis has not mentioned the coral reef crisis either in public or on his social media accounts.
In a statement, a spokesperson for the Florida Department of Environmental Protection said the state has devoted more than $50 million since 2019 for coral reef recovery and restoration but stopped short of connecting supercharged temperatures to climate change.
“While coral bleaching events due to unseasonably hot global ocean temperatures — through El Niño or some other factor — are unwelcome, this summer’s trend has been forecast previously” by federal ocean scientists, spokesperson Brian Miller said in an email to the Tampa Bay Times.
While recent spawning is hopeful, scientists say, coral recovery will require a multiyear, multifaceted approach. That includes reining back greenhouse gas emissions by curbing fossil fuel use, Moore said.
“We absolutely have to deal with the primary threats like climate change. But if we don’t also do what we’re doing right now, with restoration, there won’t be any corals left,” Moore said. “So we have to do both at the same time.”
This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative formed to cover the impacts of climate change in the state.