nature · FOLLOW YOUR CURIOSITY
A coral reef starts with tiny animals.
What looks like a rock or an underwater plant may be a colony of feeding, living polyps.
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Look closer at a colony
Corals are animals. Many live as colonies of polyps with tentacles that collect food. Stony corals build calcium carbonate skeletons, and successive generations can contribute to the structure of a reef.
If a coral stays attached to the seabed, does that make it a plant?
Reveal the idea
No. Staying in one place is not what defines a plant.
Many corals also host microscopic algae. The algae photosynthesise, and the partnership provides important benefits to the coral.
A partnership under stress
Changes in conditions can make a coral lose its symbiotic algae and appear white. Bleaching does not automatically mean the coral is already dead, but it signals stress and increases the risk of death.
AN IDEA TO TAKE WITH YOU
Many reefs are built by small animals whose lives are closely connected with microscopic partners.
Follow a connection
Sources and transparency
NOAA · Are corals animals or plants?
Accessed 2026-10-24
Prepared with AI assistance. Illustrations are explanatory, not evidence. You can report an issue in the interactive discovery.