coral

Coral refers to colonial marine invertebrates in the phylum Cnidaria, class Anthozoa. The reef-building corals belong to the order Scleractinia, commonly called stony corals. Most corals are colonial organisms composed of numerous small polyps that secrete calcium carbonate to form a hard skeleton. The living tissue of the polyps contains cnidocytes for prey capture and often hosts photosynthetic dinoflagellates, known as zooxanthellae, which provide energy through photosynthesis.

The symbiosis with zooxanthellae is a key feature of many reef-building corals, enabling rapid growth in well-lit, warm, clear waters. This relationship also makes corals highly dependent on stable environmental conditions. Coral reefs therefore typically occur in shallow tropical and subtropical seas, where temperatures are roughly 23 to 29 degrees Celsius and light levels are sufficient for photosynthesis.

Coral reefs are among the most productive and diverse ecosystems on Earth, supporting a vast array of fish and invertebrate life and providing coastal protection, tourism, and fisheries. They are, however, highly vulnerable to stressors such as rising sea temperatures, ocean acidification, pollution, sedimentation, destructive fishing practices, and disease. Prolonged stress can cause coral bleaching, the loss of symbiotic algae, which weakens corals and may lead to widespread mortality if conditions do not improve.

Reproduction occurs both sexually, through the release of gametes during mass spawning events, and asexually, via fragmentation and budding within colonies. Some corals form solitary individuals, but many species are part of extensive reef networks. Conservation aims to reduce local stressors, protect critical habitats, and support reef restoration and monitoring efforts.