Coral reef a protective area, or it may lie between the reef and the shore, and in this case is a flat, rocky area. Fish tend to prefer it when it is present. The reef lagoon is an entirely enclosed region, which creates an area less affected by wave action and often contains small reef patches. However, the "topography of coral reefs is constantly changing. Each reef is made up of irregular patches of algae, sessile invertebrates, and bare rock and sand. The size, shape and relative abundance of these patches changes from year to year in response to the various factors
Deep-water coral than tropical corals because there are no zooxanthellae to feed them. "Lophelia" has a linear polyp extension of about per year. By contrast, branching shallow-water corals, such as "Acropora", may exceed 10–20 cm/yr. Reef structure growth estimates are about per year. Scientists have also found "Lophelia" colonies on oil installations in the North Sea. Using coral age-dating methods, scientists have estimated that some living deep-water corals date back at least 10,000 years. Deep-water corals use nematocysts on their tentacles to stun prey. Deep-water corals feed on zooplankton, crustaceans and even krill. Coral can reproduce sexually or asexually. In asexual reproduction