Extreme ocean heat has eradicated two key coral species in Florida from a 350-mile-long reef that protects the state’s
coastal cities from storms and provides habitat for fisheries, scientists have found.
A record marine heat wave in 2023 killed so many Acropora corals that two species are now “functionally extinc
t,” meaning that so few remain that they’re no longer effectively adding to the coral structure, called Florida’s Coral Re
ef, according to a study published Thursday in the journal Science.
Other reef-building corals survived the 2023 Florida heat wave but the two Acropora species, commonly kno
wn as elkhorn and staghorn corals, were major contributors to reef expansion and their extirpation means a lo
ng-term decline in habitat, according to scientists. That in turn will affect marine biodiversity that supports commercially valuable fisheries.
The reef wraps around the state’s southeastern and southern coasts, which are exposed to increasingly freque
nt and intense hurricanes and tropical storms as the ocean warms. The reef dissipates wave energy from app
oaching storms, mitigating costly coastal erosion and
other damage. It’s a living organism and the demise of the Acropora species will hamper its ability to regenerate from heat waves.
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“These heavily urbanized coastlines are protected by coral reefs and the loss of the Acropora and their contributions to those reefs will have a number of casca
ding effects ecologically and economically,” said Ross Cunning, a lead author of the paper and a research biologist at the Shedd Aquarium in Chicago.
Scientists had declared a third species on the reef, Pillar coral, fun
ctionally extinct in 2020. More than 40 reef-building corals remain but they have also been affected by marine heat waves and disease.
Globally, coral reefs provide habitat for 25% of marine life and underpin an estimated $2.7 trillion a year of goods and services.
Florida’s corals had been on the decline for decades due to pollution, disease and overfishing. But a succession of eight marine heat waves since 1987 severely
weakened their resilience. Then the ninth hit in 2023, exposing the reef to temperatures greater than 88F (31C) for an average of 40 days. That triggered what the
scientists call acute heat stress, which killed corals in a matter of days. In some places, ocean surface temperatures reached a record 101F (38.3C).