USF’s Keys Marine Laboratory prepares for historic El Niño threat to Florida’s Coral Reef

By Matthew Cimitile, University Communications & Marketing, and Chris Sharp, Florida Institute of Oceanography

Record-breaking ocean temperatures triggered the most severe coral bleaching event ever documented on Florida's Coral Reef just three summers ago.

Now, with the National Oceanic and Atmospheric Administration warning of the most intense El Nino event in 150 years that could fuel another summer of exceptionally warm waters, researchers at the University of South Florida's Keys Marine Laboratory (KML) are taking action to ensure those unprecedented impacts aren't repeated.

"We know what's coming," said Cindy Lewis, director of KML. "And we are all better prepared to face an emergency crisis after our experiences from the 2023 El Niño event."

Back then, as temperatures rose, more than 5,000 coral specimens were relocated from offshore nurseries and parent colonies to KML and remained there for several months until temperatures cooled enough to be safely returned to the water.

The lab, operated by the Florida Institute of Oceanography, contains one of the largest temperature-controlled seawater systems in the Florida Keys, providing corals and other marine organisms a refuge to live, rehabilitate and grow.

Since then, the facility has expanded capacity to support even greater rapid emergency response efforts. Coral restoration partners meanwhile are working well ahead of potential escalating temperatures to ensure they are well prepared to act and support the only living barrier reef in the continental United States.

Coordinating with KML staff, conservation organizations are identifying corals in their reef nurseries that may need to be brought in for safekeeping if water temperatures climb, a proactive triage strategy informed directly by the lessons of 2023.

If temperatures escalate rapidly, this could mean identifying which corals are more valuable to save and need to be relocated to KML or to even deeper nurseries to avoid hotter, shallow waters.

"We learned that we simply cannot save them all, but we need to ensure that we can preserve a critical mass and diversity of corals to continue restoration efforts. The 2023 event forced us all to re-assess and prioritize which corals to 'rescue,'" Lewis said.

Building Capacity Before the Next Crisis

One major take-away after the 2023 coral crisis was the need for expanded land-based capacity for rapid responses. With funding support from the Florida Department of Environmental Protection (FDEP), KML just completed construction of a new temperature-controlled seawater system last month, adding 20 more seawater tables to support coral restoration.

Additional FDEP funding in this year's state budget will support another eight, bringing the total to 80 seawater tables at KML that can safely house corals during an emergency warming situation and, ultimately, return them to the reef. Each table is equipped with necessary rain covers and power heads for circulating water to keep rescued corals thriving.

The expanded capacity and support will allow KML to receive and stabilize a significantly greater number of corals than was possible in 2023. This is a meaningful step forward for a lab that already serves as a hub for some of Florida's leading conservation organizations, including The Florida Aquarium, Coral Restoration Foundation (CRF), Reef Renewal USA, Islamorada Conservation and Restoration Education (I.CARE), and the Florida Fish and Wildlife Conservation Commission - Fish and Wildlife Research Institute (FWRI).

"The Keys Marine Laboratory is uniquely positioned and equipped to support a multi-agency response to bleaching events on Florida's Coral Reef," said Gil McRae, director of FWRI. "With forecasts calling for sustained high sea surface temperatures this summer, this expanded capability will greatly increase the chances that corals that are critically important to long-term restoration goals can be spared widespread mortality from bleaching events."

A Race Against Rising Temperatures

Florida's Coral Reef stretches nearly 360 miles along the state's southeast coast. Elkhorn coral, one of the reef's most ecologically critical species, was among the hardest hit in 2023, and has been listed as critically endangered and functionally extinct on Florida's reefs. Recovery efforts, including the delivery of more than 1,050 resilient coral juveniles to KML from The Florida Aquarium in May 2025, are ongoing, making the protection of existing and recently restored corals this summer especially urgent.

When bleaching occurs, warming water stresses corals into expelling the symbiotic algae living in their tissues, causing them to turn white. Prolonged thermal stress can lead to coral death. With El Niño poised to push sea surface temperatures even higher, the window for intervention could be narrow.

"One of the clearest lessons from the 2023 marine heatwave is that redundancy saves corals," said Phanor Montoya-Maya, restoration program manager at the Coral Restoration Foundation. "When conditions deteriorate faster than anyone predicted, having multiple response options, not just one plan, is what keeps restoration efforts resilient. It is what helps save critical coral stock to continue restoring coral populations in the Florida Keys."

Besides providing the infrastructure to respond, KML's location in the middle of the Florida Keys makes it uniquely positioned to serve as a central coordination point for the reef rescue network. When temperatures spike, partner organizations can mobilize quickly to transport corals to the lab for refuge. That system and strategy helped save thousands of specimens that might otherwise have been lost in 2023.

Armed with greater capacity, a head start on preparation and lessons learned from the most severe bleaching event on record, KML and its partners enter this summer with a safety net stronger than ever before.

"Having additional capacity at Keys Marine Laboratory means more corals can be protected, monitored and cared for if stressful conditions develop this summer," said Kylie Smith, co-founder of Islamorada Conservation and Restoration Education. "Investments like this don't just benefit a single organization; they strengthen the entire restoration community's ability to safeguard years of restoration progress and respond quickly when our reefs need it most."