Why is coral an animal rather than a plant?
A coral reef is built by colonies of tiny animals, often living with microscopic partners.
Meet the coral polyp
Most reef-building corals are made of many small animals called polyps. A polyp has a mouth surrounded by tentacles and can capture tiny food particles from the water. Many polyps live connected in a colony, gradually building the hard calcium-carbonate skeleton that gives a reef its structure. From a distance, the colony can look like a plant or rock.
The partnership behind many reefs
Numerous corals also host microscopic algae within their tissues. Using sunlight, these organisms make sugars that help nourish the coral, while the coral provides shelter and nutrients. The relationship explains both the productivity of tropical reefs and their sensitivity to changing environmental conditions.
Why bleaching is a warning sign
When exposed to stresses such as prolonged marine heat, corals may lose their symbiotic algae or the algae’s pigments. Their pale skeleton then shows through, producing the appearance called coral bleaching. Bleached coral is not necessarily dead, but it has lost an important source of energy and may struggle if stress persists. Recognising coral as a living animal makes the stakes of reef conservation easier to understand.
External references are provided for exploration; Curio Hour’s explanation is written separately.