Corals survived past climate changes by retreating to the deeps

He and his colleagues chose these two species because they essentially built the Florida reef. They also grow the fastest of all corals on the Florida Reef, meaning they are essential to its ability to recover from damage. “Acropora Corals have been the primary reef builders for the past 10,000 years,” Cunning said. Unfortunately, they also showed the highest levels of mortality from heatwaves.

Coral Apocalypse

Cunning’s team discovered the mortality rate among Acropora corals reached 100 percent in Dry Tortugas National Park, which is at the southern end of the Florida Reef. Moving north to the Lower Keys, Middle Keys and most of the Upper Keys, mortality remained between 98 and 100 percent.

“Once you start moving a little further north, you get to Biscayne National Park, where mortality rates were 90 percent,” Cunning said. “Only in the northernmost part of the reef, in Miami and Broward counties, did mortality drop to just 38 percent thanks to cooler temperatures there.”

Still, the death rate was exceptionally high in most of the country. Acropora colonies across the Florida Reef. “We are facing functional extinction,” Cunning said.

But corals have been around for about 460 million years and have survived several mass extinctions, including the one that wiped out the dinosaurs. As vulnerable as they appear, corals seem to have a death escape card that they always pull when things go really bad for them. This map is most likely buried deep in their genome.

Ancestral Strength

“There have been studies done on the evolutionary history of corals, but the difference between those and our work is the technology,” said Claudia Francesca Vaga, a marine biologist at the Smithsonian Institution.

His team examined ultra-conserved elements, almost identical DNA sequences in even distant species. These elements were used to construct the most extensive coral phylogenetic tree to date. Based on genomic data and fossil evidence, Vaga’s team analyzed the relationships between 274 species of stony corals to trace their common ancestor and reconstruct their evolution from it.