A new scientific study has found that the depth of coral in the Cayman Islands determines how it reacts to extreme temperatures.
The research, published in the journal ‘Scientific Reports’ looked at how different reef depths responded during the severe heatwave in the Caribbean in 2023.
Temperatures stayed above 31°C for weeks, causing one of the worst coral bleaching events ever recorded in the region.
Scientists studied coral reefs from 10 metres to 50 metres deep off the coast of Grand Cayman.
They found that corals in shallow water were badly affected, but corals in deeper water were more likely to survive.
At 10 metres, all coral colonies showed signs of bleaching. But at 50 metres, only about one in five corals were affected.
The researchers said this was likely because the water was cooler at deeper depths.
However, the study also found that not all corals benefitted from the deeper water. Corals that normally live in shallow water were badly damaged, even when found deeper down.
On the other hand, corals that naturally live across a range of depths had a better chance of surviving in cooler, deeper areas.
“Mesophotic coral ecosystems cannot be considered universal refuges for coral biodiversity,” the scientists wrote in the report.
This means that deeper reefs – known as mesophotic coral ecosystems – might help protect some types of coral during heatwaves, but not all.
These findings are important as scientists and policymakers look for ways to protect reefs as ocean temperatures continue to rise.
The researchers recommend protecting deeper reefs and keeping a close eye on how different coral species respond to heat.
This can help guide future conservation efforts in the Cayman Islands and beyond.
The full study, titled ‘Mesophotic coral ecosystems as potential refuges during a marine heatwave in the Cayman Islands’, is available online at Scientific Reports
