Why do corals bleach?

Dead coral

Algae grows on dead coral making it impossible for new colonies to form. If there are enough fish on the reef they can clean the algae away and allow corals to return

'Bleached' coral

If high water temperatures persist for a week or more the polyps reject their plant partners and the coral appears 'bleached'. If the heat persists for too long the coral will die

Healthy coral

Tiny plants called zooxanthellae feed animal polyps through photosythesis on the coral. Interactions between the two generate corals' brilliant colours

Dead coral

Algae grows on dead coral making it impossible for new colonies to form. If there are enough fish on the reef they can clean the algae away and allow corals to return

'Bleached' coral

If high water temperatures persist for a week or more the polyps reject their plant partners and the coral appears 'bleached'. If the heat persists for too long the coral will die

Healthy coral

Tiny plants called zooxanthellae feed animal polyps through photosythesis on the coral. Interactions between the two generate corals' brilliant colours

Dead coral

Algae grows on dead coral making it impossible for new colonies to form. If there are enough fish on the reef they can clean the algae away and allow corals to return

'Bleached' coral

If high water temperatures persist for a week or more the polyps reject their plant partners and the coral appears 'bleached'. If the heat persists for too long the coral will die

Healthy coral

Tiny plants called zooxanthellae feed animal polyps through photosythesis on the coral. Interactions between the two generate corals' brilliant colours

Dead coral

Algae grows on dead coral making it impossible for new colonies to form. If there are enough fish on the reef they can clean the algae away and allow corals to return

'Bleached' coral

If high water temperatures persist for a week or more the polyps reject their plant partners and the coral appears 'bleached'. If the heat persists for too long the coral will die

Healthy coral

Tiny plants called zooxanthellae feed animal polyps through photosythesis on the coral. Interactions between the two generate corals' brilliant colours