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Florida's coal reefs are recovering after record high ocean temperatures

A MARTÍNEZ, HOST:

It's been a tough year for coral reefs around the world. Some of the highest ocean temperatures ever recorded helped spark bleaching events and coral die-offs. In Florida, marine scientists responded to the crisis over the summer with a massive rescue operation moving endangered corals to saltwater tanks on land. NPR's Greg Allen reports, months later, ocean temperatures have dropped and they've begun returning corals to their native habitat.

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GREG ALLEN, BYLINE: For decades, Florida's coral reefs, like those around the world, have faced a host of challenges. Declining water quality, overfishing, even battering by boat anchors have degraded many reefs. Disease has also played a major role, wiping out entire species and contributing to the steady decline. But this summer's ocean heatwave brought a whole new set of challenges to the reefs. As water temperatures in Florida's Keys rose over 100 degrees, dozens of groups and hundreds of volunteers scrambled to move onshore corals they were growing in underwater nurseries. But over the last month, water temperatures have dropped to a more seasonal 80 degrees. Jason Spader with Mote Marine Lab's Coral Reef Restoration program says staff are returning corals to the offshore nurseries.

JASON SPADARO: Right now, we've put back closing in on 7,000 corals so far and will be continuing those operations through at least the end of the calendar year and probably into early 2024.

ALLEN: For years now, Mote and other groups have maintained large underwater nurseries where they grow coral on PVC trees. When they're large enough, corals are transplanted onto reefs. It's all part of a program coordinated by NOAA to restore reefs that are vital not just to the environment, but also to the economy of the Florida Keys. Although many corals died in the heat wave, Spadaro says some did remarkably well.

SPADARO: We had several genotypes that showed those hallmarks of resilience that Mote's science-based restoration strategy really focuses on. And even some of our coral babies that were bred here on land and then were put out into the nurseries weathered the entire stress event without bleaching.

ALLEN: Despite the reality of climate change and the likelihood that ocean temperatures will continue rising, Spadaro is optimistic about the future of Florida's coral reefs.

SPADARO: We know that we've got the genotypes and the traits in those populations that are resilient to these stresses, and the focus really is moving those disease-resistant, thermally tolerant genotypes into that restored community.

ALLEN: For now, Spadaro says, corals are just being restored to their offshore nurseries. But soon he expects his and other groups will resume transplanting healthy corals back onto reefs.

Greg Allen, NPR News, Miami.

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Greg Allen
As NPR's Miami correspondent, Greg Allen reports on the diverse issues and developments tied to the Southeast. He covers everything from breaking news to economic and political stories to arts and environmental stories. He moved into this role in 2006, after four years as NPR's Midwest correspondent.