In 2023, a record-breaking marine heat wave caused massive areas of Florida's coral reef to lose its color, resulting in the ninth and deadliest mass bleaching event in the Caribbean. According to a recent analysis that attempts to shed light on how warming waters can be fatal for the ecosystems they have historically supported, temperatures spiked for weeks, nearly wiping out two of the oldest and most significant coral species in the area.
The analysis, which was co-authored by researchers from the University of South Florida, the National Oceanic and Atmospheric Administration, and a number of nonprofit groups, was released on Thursday in the peer-reviewed academic journal Science. It presented startling results from a study on how that record heat wave affected a 350-mile section of the Florida reef. According to the researchers, the reef wilted as sea surface temperatures stayed at or above 31 degrees Celsius, or 87.8 degrees Fahrenheit, for an average of 40.7 days during the summer.
According to Ross Cunning, one of the report's lead authors and a biologist at the Chicago-based Shedd Aquarium, whose research focuses on ways to make coral reefs more resilient against the effects of climate change, the heat stress in some areas of the reef during that time was up to four times greater than it had been during any previous heat wave or any previous year that scientists recorded temperature data for the area.
The mortality of staghorn and elkhorn coral, which are referred to as "reef builders" because they have supplied the structural basis from which Caribbean reef ecosystems can flourish for thousands of years, were among the heat wave's most catastrophic effects. Between 97.8% and 100% of those two species' coral died during the heat wave, according to the report, which researchers described as "their functional extinction from the region."
"Functional extinction" refers to the loss of sufficient numbers of either coral species in the Caribbean for staghorn or elkhorn to carry out their long-standing functions for the reef as a whole.
"These corals are the ecosystem engineers of reefs," Cunning stated in an interview with CBS News. "They literally build the three-dimensional framework that we know as the coral reef."
"What you're left with is a range of smaller trees and shrubs and other plants, and they'll continue to grow and form together some type of forest," Cunning said, comparing the "huge losses" experienced by the Caribbean reef in their absence to those that a diverse forest might experience after losing its largest and most important trees: "but it's a forest transformed without these major contributors."
The Florida reef's 2023 heat wave has been characterized as a bleaching event, in which rising oceans cause corals to lose their vibrant algae and turn white and fragile. Over time, bleaching kills coral by depriving them of nutrients and increasing their susceptibility to illness. However, according to John Parkinson, a marine ecology professor at the University of South Florida and another co-author of the current paper, the conditions in this instance were so dire that they actually sped up that process in some of the impacted reefs.
"Coral bleaching is definitely a problem, but some of these corals didn't even get a chance to bleach," Parkinson stated to CBS News. "In actuality, they have only begun to dissolve." Coral bleaching is definitely a problem, but some of these corals didn't even get a chance to bleach," Parkinson stated to CBS News. In actuality, they have barely begun to dissolve. They were basically shedding their tissue.
According to specialists, the effects of the 2023 heat wave are probably irreversible. As global warming has raised ocean temperatures worldwide, coral reefs have become the first environmental system on Earth to cross a climate "tipping point," according to a report published earlier this month by climate scientists at the University of Exeter's Global Systems Institute in England.
According to the Global Systems Institute, coral reefs provide over 1 billion jobs and provide habitat and protection for nearly 25% of all marine species. Climate scientists have also observed that reefs protect coasts and the communities that inhabit them from erosion, flooding, and storm surges in Florida and other places.
Without further efforts to lessen the usage of fossil fuels and the greenhouse gas emissions that remain in the atmosphere after they are burned, scientists predict that heat waves will grow more frequent and powerful. "The frequency and severity of extreme climate and weather events, including marine heat waves, are increasing, resulting in widespread degradation of the function, structure, resilience, and adaptive capacity of ecosystems," the co-authors stated in recent research published in Science.
They emphasized that these are not grounds to give up on a better future. Parkinson described the record heat wave as "devastating" and "off the charts," but he also told CBS News that he prefers to hold onto hope that things can improve.
"You know, some corals survived, and the people who are involved in restoration are still going at it, and we're still trying to keep corals around," he stated. "We all believe that we can, but we really need help from the people who have the power to adjust our approach to these climate policies."
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