Pupil lesson
Why can a coral turn white?
Read, think and draw. Use paper or a document provided by your teacher. You do not need an account or to send personal details to KEO.
Read and wonder
Corals are animals. Many reef-building corals have tiny algae inside their tissues. The algae use sunlight to make food and share some with the coral. They also provide much of its colour.
Stressful conditions, such as water becoming too warm, can cause the loss of these algae. The pale skeleton shows through: coral bleaching. A bleached coral is not necessarily dead. It may recover if conditions improve, but prolonged stress can kill it. Protecting water quality and reducing the emissions warming the ocean are parts of the wider response.
Three things to know
- Corals are animals.
- Many reef-building corals have partner algae.
- Bleaching signals stress, not automatic proof of death.
- Coral with partner algae
- Stress can cause loss of algae
- Coral becomes pale and vulnerable
Words to explore
- Bleaching
- A coral becoming pale after losing many of its partner algae.
- Symbiosis
- A close relationship between different kinds of living things.
Think it through
1. Is a coral an animal or a plant?
2. What do partner algae provide?
3. Is every bleached coral dead? Explain.
Try it
Draw a coral with algae, a bleached coral and two possible outcomes. Add conditions that could help recovery. Use patterns as well as colour.
Sources and credits
Lesson summary and activity prepared for Kids.Earth.Org. Factual sources checked 5 November 2026.