University of Miami Rosenstiel School scientists are pulling bubble-wrapped Elkhorn coral from a large cooler.
They're yellow-brown with flat, antler-like arms.
"Here's another beautiful one right here,” one scientist said unwrapping one of the branching stony corals.
They're functionally extinct in Florida’s wild barrier reef, along with staghorn coral, thanks to ocean temperatures reaching up to 100 degrees three years ago.
"We're in the midst of a thermal rescue operation,” said Cameron McMath, who supervises UM's Coral Reef Futures Lab at the Rosenstiel School of Marine, Atmospheric & Earth Science here on Virginia Key.
His team is rescuing these sensitive corals from warming waters ahead of another bleaching event expected this summer. A predicted "super" El Niño climate pattern has scientists on edge, after a similar phenomenon in 2023 broke records — bleaching up to 100% of certain coral species with near-total mortality in some cases.
The UM researchers have now collected about 30 different genetic types of Elkhorn coral from offshore nurseries where they're grown before being planted in the wild. They brought them to temperature-controlled tanks on land.
"We like to think of it as a Noah's Ark operation,” McMath said.
Florida corals start to bleach when the water reaches 87 degrees Fahrenheit. The stressed corals release the microscopic algae that gives them their color and feeds them. Some corals starve to death while others bounce back.
But these rescued corals aren't showing signs of heat stress ... yet.
"This is us reacting in a sort of more early stage before things get too bad out there,” McMath said.
There are some reports of bleaching along the barrier reef right now, although, recent tropical activity in the Gulf temporarily cooled the water temperature.
In mid-June some areas recorded up to 92-degrees.
"This is really unusual because prior to 2023, we never saw those temperatures until August and September, the hottest time of the year,” said Andy Bruckner with the Florida Keys National Marine Sanctuary, a branch of the National Oceanic and Atmospheric Administration.
The federal agency publishes Bleaching Alerts using satellite temperature data.
"We're looking at how hot it is, and then the second thing is: how long has it been hotter than what the normal baseline is?" Bruckner said.
These warnings, determined by temperature and duration, are measured in what's called "degree weeks” – when the water is one degree Celsius higher than what it should be for a number of consecutive weeks.
For example, a Bleaching Warning equates to what scientists call “four-degree weeks,” or rather four consecutive weeks of one-degree Celsius elevation. Bleaching Alert Level 1 is up to eight weeks.
We're at Bleaching Alert Level 2 right now, which could be 12 weeks with the elevated temps. That was once the highest and worst alert … until 2023.
“We now have an Alert Level 3, which is if there's up to 16-degree heating weeks. Alert Level 4 is 20-degree heating weeks, and Alert Level 5 is greater than 20-degree heating weeks,” Bruckner explained.
Since 2023, he added that a lot is being done to prevent another massive die-off.
Researchers are producing new corals using the genes of those more resilient to heat, they've established two gene banks and they are doing cooling experiments, like canopies that float on the water.
"The idea is that we're going to put this on top of the nurseries to be able to shade a larger area, and we're going to measure the temperature and how much light is getting through, and then see what happens to the coral, so that we see if this is something that we can expand in future years when it gets really hot,” Bruckner said.
Researchers are also getting additional permitting for deep water nurseries where it’s cooler and more protected from sunlight.
Back on Virginia Key, the rescued Elkhorn corals will remain in temperature-controlled tanks for the next three to five months, at least.
UM's Cameron McMath said about one-third of all marine life lives on a reef at some point.
"If you lose coral, you stand to lose a third of all marine life, which you can imagine would be catastrophic for the food chain,” he said.
So, protecting the barrier reef from extreme heat is so important, he said, not only for biodiversity, fisheries and tourism, but also to shield our coastlines from harmful wave action.
