Scientists have discovered that two of the key coral species forming Florida's reef are now ecologically extinct following a withering ocean heatwave caused devastating losses.
The near-total decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their once vital role in building and sustaining reef ecosystems that support a variety of marine life.
Functional extinction is a stage preceding total extinction, a danger that now looms for many coral species.
Scientists recently alerted that a tipping point had been reached, whereby corals globally are likely to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.
"Time is running out," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without swift, decisive measures to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."
The recent study, published in the Science journal, examined the outcome of staghorn coral and elkhorn corals off the Florida coast after a severe marine heatwave in 2023.
This event raised temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.
The two species are complex, reef-building corals and are named because they look like, respectively, the horns of stags and elks.
However, researchers who conducted diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.
The two Acropora species had already endured from decades of regional pressures in Florida, such as poor water quality from pollutants that wash off the land, as well as illness.
But the 2023 marine heatwave has proved lethal for these temperature-sensitive species.
The 2023 event caused the ninth occurrence of bleaching on the Florida reef – a process whereby corals become heat-stressed and expel the symbiotic algae living in their tissues, causing them to become ghostly white.
If temperatures stay high, the corals die off entirely.
Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate crisis.
This poses a significant danger to:
Corals also serve as a protective barrier to protect our shorelines from intense hurricanes, which are themselves being intensified by increasing global heat.
In a desperate attempt to prevent a decline of threatened corals, scientists have established collections of Acropora in aquariums and offshore coral nurseries.
Efforts have been made to replant corals on reefs in Florida, as well, in an effort to restore some of the ninety percent of coral cover lost off the state in the past four decades.
But as global heating continues to intensify, there is little hope of long-term survival of these species without major interventions, scientists caution.
"Elkhorn species, in particular, are some of the key wave-dampening coral species in the area," noted a study co-author, a ocean scientist at the Miami University.
"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals altogether."
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