Hard Corals
Phylum: Cnidaria | Order: Scleractinia
Coral is composed of individual organisms called polyps, each equipped with stinging tentacles for defence and capturing prey like plankton and small fish, similar to the tactics of sea anemones. Food enters the stomach through the mouth. After the food is consumed, waste products are expelled through the same opening. This is how coral polyps feed at night. During the day, the zooxanthellae provide nutrients for the coral through photosynthesis. As a mutualistic symbiosis, the coral provides shelter for the photosynthetic algae in return. Hundreds to thousands of polyps grow together to form a coral colony. Hard corals create skeletons from calcium carbonate, a hard substance that eventually becomes rock. Overtime, this rock builds up to form the foundation of a coral reef and provides a structure upon which baby corals can settle. Soft corals, lacking calcium carbonate are fleshy and flexible, often resembling trees or fans.
