Impact of mass bleaching event on Florida coral reefs far worse than scientists feared

MIAMI-DADE COUNTY, Fla. – Scientists are calling it the worst coral bleaching event in Florida’s recorded history. Millions of corals starving to death because of the extremely hot ocean temperatures over the summer.

Local 10 News’ Louis Aguirre recently met up with a team of coral researchers from Chicago’s famed Shedd Aquarium, who were hoping to save some precious coral branches from Dry Tortugas National Park.

What was once a thriving marine ecosystem is now a coral graveyard.

It was supposed to be a rescue and recovery mission in Dry Torturgas National Park, about 68 miles west of Key West.

“That’s a location where the staghorn corals were flourishing,” said Ross Cunning, a research coral biologist with the Shedd Aquarium. “There was large, healthy populations of those corals, which we surveyed and studied and collected in June.”

But in July, reports spread of a mass bleaching event that was devastating the Florida Keys, already in the grips of what was to be the hottest summer ever recorded planet earth.

“When this bleaching event started to unfold, we realized we needed to go back much sooner to see how these corals were doing and learn as much as we could from those corals and how they were responding to a natural bleaching event,” said Cunning.

So the team of coral biologists from Shedd Aquarium joined scientists from the University of Miami and other institutions on board Shedd’s RV-2 research vessel for the urgent expedition.

They went back to survey the reef track in the Florida Keys with a NOAA permit to bring back up to a thousand branches of critically endangered staghorn corals from the Dry Tortugas and bring them to an on-land facility at the University of Miami’s Rosenstiel School...but it was too late.

“As we got further south in the trip, and we started doing these surveys and looking around, we just weren’t seeing any, any of those survivors,” said Dr. Shayle Matsuda, post-doctoral researcher with Shedd Aquarium.

Ocean temperatures were already dangerously high, causing millions of corals to lose their symbiotic algae that feeds them and gives them color, turning them bleach white as they slowly starved to death.

“After three days of diving comprehensively across the National Park, in the Tortugas, 35 different locations where we had previously observed healthy populations of staghorn corals in June, just a couple of months ago, and we found that they were all dead,” said Cunning.

Added Matsuda: “To see something on this scale, it’s really tough to, emotionally to see. These animals that you care about, that you’ve been working so hard to study to understand, to just literally die in front of your eyes.”

It was a huge blow. Researchers thought those particular staghorns could be the key to saving the corals of tomorrow. They had survived heat stressors and disease in the past.

“We were actually testing their heat tolerance to identify individual strains of staghorn coral that have higher or lower heat tolerance that may be better able to withstand coral bleaching events,” said Cunning.

It’s now October and ocean temperatures are cooling down.

In fact, some of the bleached coral Local 10 News reported on in August at Cheeca Rocks near Islamorada is already starting to bounce back.

But those mounding corals are more resilient. It’s the branching corals that may be lost forever.

“We documented 90-95%, severe bleaching across coral species throughout the Keys and the Dry Tortugas,” said Cunning.

The endangered staghorn and elkhorn coral the team surveyed were nearly all dead. Populations had just collapsed in such a short period of time.

“It’s like losing the trees and rainforest to lose the corals,” said Matsuda. “Without the corals, the whole ecosystem will just literally start to crumble. And so instead of having this really diverse, thriving space, when you lose those corals, those coral skeletons start to break down, and you’re literally watching the whole ecosystem crumble before your eyes.”

Twenty-five percent of all marine life depends on healthy coral reefs, and it’s not known what the long term effects will be of this bleaching event.

The planet is only getting warmer and unless we address climate change with the urgency this moment in time is calling for, scientists fear events like this will continue to happen all over the world.

“Every tenth of a degree of additional warming matters,” said Cunning. “Every bit of warming that we can prevent will lead to greater survival of corals in the future.”

Added Matsuda: “And so that nugget of hope is that there are still corals, they are still alive out there. And this is the perfect time for folks to engage in a level that they haven’t before.”

The hope is that many of the bleached corals will somehow recover now that ocean temperatures are finally cooling back down, but even if they come back, those corals are now much more stressed, leaving them more susceptible to disease.

The final assessment of just how devastating this summer was to our reefs is still not known. Since the 1970s, Florida’s reefs have lost more than 90% of their coral cover.

That’s why coral research is so important, finding those heat and disease tolerant strains and propagating them.

RELATED LINKS

https://www.sheddaquarium.org/about-shedd/support-us

https://rescueareef.earth.miami.edu/


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