Scientists have recently discovered a reef off the Florida Keys have been completely bleached by a marine heat wave, leading to concerns about the ecosystem’s long-term stability.

Scientists said recent dives by experts from NOAA’s Atlantic Oceanographic & Meteorological Lab around the Cheeca Rocks reef made the grim discovery.

“I’ve never seen anything like it,” said Ian Enochs, a research ecologist and lead of NOAA’s AOML coral program.

“The corals at our primary climate monitoring reef site, Cheeca Rocks, are completely bleached. No single coral is untouched. It’s shocking.”

Photos from the expedition show what are usually bright-colored coral are now pale white and exemplify symptoms of heat stress.

Marine experts say that when water temperatures get too warm, algae produce toxins that are eventually expelled by the coral.

Thermal stress begins when water temperatures reach 88 degrees, but some observation sites around Florida have reported water temperatures in the 90s.

An extensive bleaching event was expected due to El Niño, but biologists said the consequences have passed their expectations. 

Due to the record heat, some experts predict difficulties for the corals in the southern Gulf of Mexico and the Caribbean could persist well into October.

“I’m worried because it’s so early in the season, and they may continue to be stressed for some time,” Enochs said.

“This is more bleaching than I’ve seen, earlier than I’ve ever seen it. We still have a warm South Florida summer ahead of us, which means more stressful conditions.”

Despite the alarming event, Enochs said that bleaching doesn’t always lead to mortality and corals are known to recover when waters cool.

The lab is expected to continue its extensive observations through the remainder of the year to further understand the impacts on the ecosystem and how long it could take the corals to recover.

Several groups are working to try to save corals by growing new batches at land-based facilities.

They admit that even though recent news has been tough, they are not giving up hope.