All of the Florida Keys reef is under thermal stress — meaning the water is warm enough that corals may start bleaching.
Corals bleach when they expel the algae that feed them and give them color. Bleaching can be fatal to corals, though some do recover.
The current coral bleaching alert is at the highest level for the Florida Keys National Marine Sanctuary. That's according to the Coral Reef Watch, a federal program that tracks sea temperatures.
That doesn't necessarily mean there will be a mass bleaching event. But divers have reported 50 cases of paling or partial bleaching in the last few weeks.
There's nothing you can do to stop coral bleaching once it starts — but scientists want citizen observations so they know where and what kind of corals are being affected.