Coral Reefs
Underwater structures built by tiny animals that cover less than 1% of the seafloor but support roughly a quarter of marine species.
- Largest reef
- Great Barrier Reef, Australia
- Main threats
- Warming seas, ocean acidification, pollution, overfishing
How a reef forms
Corals are animals that live in partnership with algae, which supply them with food through photosynthesis. Over centuries, their limestone skeletons accumulate into reefs.
Bleaching
When seawater stays too warm, corals expel their algae, turn white and can starve. Repeated marine heatwaves have caused mass bleaching events on reefs around the world.
Why they matter
Reefs shelter fish that feed millions of people, protect coastlines from waves and support tourism.