How do coral polyps build reefs?
Reef-building stony corals are colonies of small polyps that secrete calcium-carbonate skeletons.
Body plan, feeding and the marine environment
Each polyp lives on a skeletal cup, and new layers accumulate over older structure as the colony grows. Photosynthetic algae in tissues provide energy and support calcification, while tentacles also capture plankton. Branching, massive or plate forms vary with light, waves and sediment. Relationships among marine invertebrates cannot be inferred from appearance alone because similar forms can evolve in different lineages. Pressure, light, temperature, salinity and currents shape feeding and movement. Laboratory observations may not represent the full behavior seen in nature.
Ecosystem function, defense and conservation
Over long periods, coral skeletons and other calcifying organisms build a three-dimensional reef that shelters many species. Prolonged heat stress can cause loss of algal partners and bleaching. Acidification challenges calcification, while pollution and overfishing disturb ecological balance. These animals may shape ecosystems through filtration, decomposition, sediment mixing or reef building. Warming, deoxygenation, acidification, plastic, seabed damage and overharvest are considered together. Conservation targets habitat processes as well as individual species.