Miami, Florida – Off Florida's coast, a team of scientists and trained volunteers are on the front line of coral research and planting. They are examining how different coral species are faring in increasingly warm waters.
The University of Miami's long-running Rescue a Reef program aims to advance conservation efforts and raise public awareness.
Their work also involves researching which coral species can withstand rapidly warming oceans due to human-caused climate change.
"Certain species may be more resilient, where they're able to better survive and recover from thermal stress events," program manager Devon Ledbetter explained to AFP during a recent dive to Rainbow Reef about three miles offshore from Key Biscayne.
Coral reefs support vibrant marine ecosystems, but also act as breakwaters, protecting coastlines from storm-driven erosion and flooding.
The situation, however, is increasingly dire.
Vital coral species are dying in heating oceans
A record-breaking marine heat wave that began in 2023 left two ecologically vital coral species, elkhorn and staghorn, "functionally extinct" in Florida's Coral Reef.
This fact highlights the growing dangers a warming climate poses for the world's oceans.
The National Oceanic and Atmospheric Administration (NOAA) believes that this fourth global coral bleaching event likely concluded in mid-2025.
But they warn that a strong El Niño could cause more widespread bleaching around the world and in Florida's waters.
Rescue a Reef divers have multiple coral planting methods. Some coral species with fast-growing branches are planted onto "coral trees" that look like old television antennas and are suspended in the water column. Floats keep them upright.
Other corals are placed onto table frames fixed to the ocean floor. Some are mounted onto plugs, screwed into a three-hole "cookie," and planted onto the reef. These get protective umbrellas to protect them from hungry fish.
Researchers use color reference charts placed around newly planted coral to record the pigmentation. This allows them to monitor coral health and detect early signs of heat stress.
Rebuilding the ecosystem "one coral at a time"
Coral is made up of tiny individual animals called polyps, which maintain a symbiotic relationship with microscopic algae that live within their tissues. When the algae are stressed by heat or pollution, they leave, causing the coral to "bleach" and become vulnerable to disease and death.
"Anecdotally, we've seen that Mountainous Star Coral tends to be the most resilient to bleaching and thermal stress," Ledbetter explained. So far this summer, the program has planted 615 corals, with 228 of those part of the thermal bleaching study.
The program began in 2015. Ledbetter explained they want to advance science, educate the public, and rebuild the ecosystem "one coral at a time."
The risks have never been higher. Even as this fourth global bleaching event comes to an end, sea surface temperatures are still higher than they were 25 to 30 years ago, when the first global coral bleaching event occurred, according to recent research published by NOAA.