Florida’s ailing coral reef system is at the risk of a devastating bleaching outbreak after being engulfed in an “unprecedented” heat stress event that stretches throughout the waters of the Caribbean and Central America, US government scientists have warned.
South-east Florida’s corals are now at the highest alert level for bleaching for the first time ever, according to the National Oceanic and Atmospheric Administration (Noaa), with “significant mortality likely” for its corals amid abnormally hot ocean temperatures.
The coral reef has been exposed to water temperatures this summer that at times have more resembled a hot tub, with the heat stress arriving five to six weeks earlier than any previous similar event. The severe heat and prolonged nature of this heat – ocean temperatures are likely to remain elevated for another month – has placed Florida’s corals, particularly around the Florida Keys region, at severe risk.
“The temperatures have clearly been higher than anything ever recorded before,” said Derek Manzello, coordinator of Noaa’s coral reef watch program. “You hear the word ‘unprecedented’ get thrown around a lot but Florida’s corals have never been exposed to this level of heat stress before.
“The big concern here is that the Florida Keys corals will experience a mass mortality and that will push the reef ecosystem towards a trajectory of degradation, with severe ramifications in terms of the ecological services it provides.”
Florida’s reefs are some of the most visited in the world by scuba divers and, as a treasure trove of marine life, a prized site for species such as spiny lobsters, snappers and stone crabs favored by fishers. But the corals have suffered deterioration over the past 50 years due to pollution and, increasingly, bleaching events due to the rising ocean temperatures caused by the burning of fossil fuels – there have been eight bleaching events since 1987.
Scientists estimate that about 70% of Florida’s reefs are losing material, with this erosion hastened by bleaching, which occurs during periods of spiking heat. When it gets too hot, algae leave the tissue of corals, leaving them white, or bleached, in color. If this persists, the coral is vulnerable to disease and can die. At the current rate of global heating, the world is on track to lose almost all of its corals.
Despite efforts to manually replant some lost corals on Florida’s increasingly threadbare reef, the current heatwave roiling oceans around the world looks set to be a hammer blow to the ecosystem, risking not only the many species that rely upon it but also the protective buffer to storms it provides to people living near Florida’s coast.
Florida is the epicenter of an extreme phenomenon that means that the region is “marching towards a Caribbean-wide heat stress event in a matter of days of weeks”, according to Manzello. The risk to corals extends all the way down to South America, with confirmed coral bleaching off Mexico, Costa Rica, Cuba and Colombia.
“The heat event unfolding along the Meso-American Reef is literally off the scale,” tweeted Terry Hughes, a coral reef scientist at James Cook University in Australia. “A devastating blow to Mexico, Belize, Guatemala and Honduras, and elsewhere in the Caribbean.”
The loss of corals could be even more widespread, with Noaa forecasting that the world may soon be in the grip of a coral bleaching disaster on the scale of, or even surpassing, the huge bleaching event that occurred in 2016. “We are concerned we are potentially moving towards a global event. All the indicators are in line with that happening,” said Manzello.
The stark warning over the world’s corals, which sit on the frontlines of the climate crisis, came as Noaa outlined the extreme heat that has enveloped much of the world. July was the hottest month ever recorded by modern instrumentation, the agency confirmed, with a nearly 50% chance that 2023 will be the hottest ever year.
The heat, driven by human-caused climate change, is fueling disasters such as flooding and deadly heatwaves. In the US alone, Noaa said, there have been 15 disasters that cost at least $1bn in damages in the first seven months of the year, which is a record. This doesn’t include the catastrophic fires in Maui, Hawaii, where at least 110 people are thought to have died in an event scientists say was worsened by hot, tinderbox-like conditions.
“This has been the summer of extremes,” said Sarah Kapnick, Noaa’s chief scientist. “Climate change is enhancing certain extreme events. We will see these events increase in magnitude for every additional ton of greenhouse gas we put into the atmosphere.”
