Characteristics of Coral Reefs • Coral is actually a living animal. • Coral has a symbiotic relationship with ‘zooxanthellae’ microscopic algae which live on coral. • Instead of living on the sea floor, the algae lives up on the coral which is closer to the ocean surface and so the algae get adequate light. • Zooxanthellae assist the coral in nutrient production through its photosynthetic activities. • Photosynthetic provide the coral with fixed carbon compounds for energy, enhance calcification, and mediate elemental nutrient flux. • The majority of coral reefs are found in tropical and sub-tropical water, there are also deep water corals in colder regions. • They occur in shallow tropical areas where the sea water is clean, clear and warm. • Coral reefs are one of the most productive and complex coastal ecosystems with high biological diversity. • The builders of coral reefs are tiny animals called polyps. As these polyps thrive, grow, and then die, they leave their limestone (calcium carbonate) skeletons behind. • The limestone is colonized by new polyps. Therefore, a coral reef is built up of layers of these skeletons covered ultimately by living polyps. • The reef-building or hermatypic corals can form a wide range of shapes. Coral reefs may be branched, table-like, or look like massive cups, boulders or knobs.