Bleached Elkhorn coral in Dry Tortugas National Park

Shown here is a colony of the threatened Elkhorn coral, Acropora palmata, in Dry Tortugas National Park that has become "bleached," that is, lost all its algal symbionts (also called zooxanthellae) because of the summer 2023 ocean-heat wave. These symbiotic algae that normally give the coral its color and are responsible for the coral’s nutritional wellbeing. Corals that experience bleaching can recover if ocean temperatures cool off, but after being bleached for about eight weeks, they will start to starve and die.