Alex Harris (Miami Herald/Tampa Bay News) writes about the harsh truth facing Caribbean coral reefs, stressing that, in Florida, “Scientists found that the water got so hot so fast that the corals cooked to death in a matter of days.”
The marine heat wave that gripped Florida in 2023 was hotter than anything the state has seen in 150 years, and claimed at least two victims — species of corals now marked “functionally extinct” from Florida’s reefs.
That finding comes from a newly published scientific paper that reads more like an obituary for two of the most visible and important coral species on Florida’s reefs: elkhorn and staghorn corals. In 2023, the ocean was warmer than it had ever been. When corals spend too long in hot water, they spit out the algae that live within their bodies, providing them food and shade.
Without them, corals are ghostly white and bleached. If they stay bleached for too long, they starve and sunburn to death over a few weeks. But in 2023, scientists saw something new for Florida. The water got so hot so fast that corals cooked to death in a matter of days.
The paper, published Thursday in the journal Science, was co-authored by nearly 50 Florida coral reef scientists who painstakingly surveyed Florida’s reefs from Broward County to the Dry Tortugas to tally up the damage from the historic heat wave two years ago, the ninth major bleaching event in the region. The results were dramatic. In the Dry Tortugas and Florida Keys, 97.8% to 100% of those branching coral colonies died, the scientists found. The death toll was less in the slightly cooler waters off the coast of Miami-Dade and Broward — more like 38% of colonies died. [. . .]
A death blow for three coral species
Branching corals had been on the decline for decades. About 80% of the population died since the 1980s, mostly due to disease. The marine heat wave was just the final death blow. Scientists found that enough of those species of corals died that they are now “functionally extinct,” a non-exact term that means there aren’t enough left to keep reproducing naturally on their own. “The corals that are remaining on the reef, even though there are some, are no longer serving the function that they typically do. They’re not really able to repopulate,” Karp said.
This is the third such species that has earned this label since 2020, when scientists declared the pillar coral functionally extinct. A paper published earlier this month in the journal Frontiers found that there are only 23 pillar corals left on Florida’s reef — most with live tissue smaller than a golf ball. [. . .]
For full article, see https://www.tampabay.com/news/environment/2025/10/27/2-more-florida-corals-are-functionally-extinct-after-2023-heat-wave/
[Photo by D.A. VARELA | Miami Herald/TNS: Dead coral sits in a pile near Paradise Reef nursery during a Rescue A Reef coral restoration dive out of Diver’s Paradise dive shop at Crandon Marina in Key Biscayne on Aug. 4, 2023. Two species of corals are now considered “functionally extinct” from Florida’s reefs after the marine heat wave that gripped the state in 2023.]