Rescued corals return after historic ocean heat

The University of South Florida announced that its team of researchers is prepared to reintroduce thousands of corals, rescued from record-breaking water temperatures, back into the ocean.

Why it matters: The news comes three months after "unprecedented heat waves and escalating water temperatures" caused a massive coral bleaching event that put the reefs at greater risk of dying.

• Coral reefs provide shelter for a quarter of ocean animals. They're also a major driver of tourism in Florida.

How it works: Warm water corals have a narrow temperature range in which they thrive, Axios climate reporter Andrew Freedman writes.

• When the water is too warm, they expel algae that live in their tissues, which causes them to turn white (an event known as coral bleaching.) Bleached corals are more susceptible to further heat stress.
• Ocean temperatures surrounding South Florida and the Florida Keys reached historic levels this spring and summer, and hit records unusually early in the warm season.

Zoom in: The return of rescued corals is a sign that water temperatures have dropped somewhat, but don't yet signal an "all-clear."

• They may be more susceptible to disease outbreaks in the next three to six months, Cynthia Lewis, director of the Florida Institute of Oceanography's Keys Marine Laboratory, operated by USF told Axios in an interview.

What's next: USF said its Keys Marine Laboratory housed more than 5,000 rescued corals throughout the months-long heat wave.

• Coral reefs will be returned first to underwater nurseries to "grow under the care of researchers" before ultimately being reattached to natural reefs via epoxy, cement, zip ties and nails.

What they're saying: "USF can be proud of the incredible impact their investments ... are having on the recovery of Florida's most vulnerable coral reef ecosystem," Monty Graham, director of the Florida Institute of Oceanography, said in a statement.