Keys corals begin to pale as water temperature rises

As a long, hot summer drags on and Florida Keys water temperatures continue to rise, coral reefs are beginning to change from their bright colors to pale, a precursor to bleaching.

Since July 9, water temperatures on the reefs throughout the Keys have reached the threshold for bleaching. Some off of the southern reefs in the Keys, such as Looe Key, Eastern Dry Rocks, Sombrero and the inshore patch reefs, started reaching the bleaching temperature threshold as early as July 1, NOAA’s Mission: Iconic Reefs Research and Monitoring Coordinator Kathryn Lesneski said.

Healthy corals require a temperature range between 73 to 84 degrees Fahrenheit. If water temperatures remain above 87 degrees for a significant period, corals will begin to experience bleaching.

“There are a lot of reports of paling, but no reports of bleaching yet from my team,” Lesneski said.

Coral reefs on the bayside of the Keys have reached an “Alert Level 1,” and the reefs on the oceanside have reached the less dire level of “warning,” but that level is expected to increase to “Alert Level 1,” said Lesneski, citing Mote Marine Laboratory’s BleachWatch program. The threat level ranges from “no stress” to “watch” to “warning” to “alert level 1” to the most severe, “alert level 2.”

While the water temperatures are increasing, they are still below what caused a mass bleaching and coral mortality event last year, Lesneski said.

With the rise in sea temperatures this year, coral restoration practitioners in the Keys have halted outplanting corals from nearshore nurseries to the reef tract. The rising temperatures come as corals will start to spawn during the next several weeks to months. Last summer’s bleaching event could impact coral’s ability to spawn, as the coral are using a majority of energy to heal themselves.

Last year, some corals did spawn, even ones that bleached, said Jennifer Moore, NOAA’s threatened coral recovery coordinator.

NOAA and the Florida Keys National Marine Sanctuary do plan to have people out on and in the water during the spawn to monitor the activity, Moore said.

Not all the news is dire this summer. Several coral restoration projects and initiatives in the Florida Keys have been chosen for millions of dollars in federal funding under the bipartisan Infrastructure Law and Inflation Reduction Act, which support habitat restoration efforts that are designed to strengthen the climate resilience of coastal ecosystems and communities.

NOAA has designated $7 million to Mote Marine Laboratory & Aquarium to restore coral reefs at multiple sites in the Florida Keys National Marine Sanctuary, focusing on reefs associated with the Mission: Iconic Reefs effort — an unprecedented, decades-long approach to restore iconic coral reef sites in the sanctuary. They will outplant multiple species of coral, including threatened staghorn and elkhorn coral, as well as massive reef-building species such as brain, boulder and star corals. They will also significantly increase the production and release of Caribbean king crabs to help combat algae.

Mote proposes to outplant 242,000 corals on the Keys reef in the next four years, according to Jason Spadaro, Mote scientist and program manager for Coral Reef Research and Restoration at its Summerland Key facility. Mote has outplanted 240,000 corals between 2008 and 2023. The latest effort will be a “massive increase in the scope and scale” of Mote’s coral restoration work.

Mote is currently raising thousands of king crabs and plans to release 35,000 on the Keys reefs, Spadaro said.

The University of Miami will also receive $16 million in a three-year period to work with its partners to scale up strategies to increase the heat tolerance of restored corals, by focusing on corals that survived the summer 2023 heating event and conditioning early life stages of corals to prepare them for warmer temperatures. The project will use its partner network to restore tens of thousands of corals at key sites in South Florida and the Florida Keys, including Mission: Iconic Reefs locations.

Scientists with the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science traveled to Honduras to source new coral parents to help Florida’s corals survive climate change, according to University of Miami representatives.

This scientific initiative aims to study and breed corals from a unique site in Tela Bay, off the northern coast of mainland Honduras, where corals routinely experience temperatures that would normally cause widespread coral bleaching elsewhere, university representatives said. These reefs also experience freshwater impacts from a local lagoon and are often characterized by turbid, low-visibility conditions. Yet corals in the bay are thriving and appear to have shown tremendous resilience to heat stress and disease. Elkhorn corals, in particular, occur in abundance along sections of the shallowest areas.

Led by Andrew Baker, professor of marine biology and ecology and director of the Coral Reef Futures Lab at the Rosenstiel School, and including three graduate students — Alexandra Wen, Fabrizio Lepiz Conejo and Cailyn Joseph — the group worked in collaboration with Antal Borcsok, long-time advocate of the unique value of the reefs in Tela and co-founder and CEO of Tela Marine, a local science organization and aquarium.

Baker’s lab collected hundreds of DNA samples from ten species of corals around the bay and will study the genetic factors and key attributes contributing to the resilient nature of corals from this unusually warm reef. They also collected 13 live fragments of elkhorn coral and 21 small brain coral colonies that they brought back to Miami in a world-first attempt to directly breed corals from different countries in an attempt to increase their heat tolerance, university representatives said.

NOAA has yet to permit the University of Miami from introducing any of the coral offspring into the wild, as that “needs to be done thoughtfully and carefully” as to “not create other genetic concerns,” said More said. “With elkhorn coral loss, it (University of Miami’s proposal) definitely needs to be considered,” Moore said during a recent briefing with a group of reporters, including The Keys Citizen.

University of Miami’s partners will also provide bilingual education and community science opportunities in seven South Florida counties focused on how coral restoration contributes to creating healthy reefs that are part of Florida’s cultural identity.