Coral Reef, ridge or elevated part of a relatively shallow area of the seafloor approaching the sea's surface. It is formed by a rocklike accumulation of calcareous (calcium-containing) exoskeletons of Coral animals, red algae, and mollusks. Built up layer by layer by living corals growing on top of the skeletons of past generations, coral reefs grow upward at rates of 1 to 20 cm per year. Coral reefs are tropical, extending to about 30° north and south of …showed first 75 words of 372 total…

…showed last 75 words of 372 total…found in the warm, clear, shallow waters of tropical oceans worldwide. Reefs have functions ranging from providing food and shelter to fish and invertebrates to protecting the shore from erosion. Through symbiosis with unicellular algae (zooxanthellae), reef-building corals are the source of primary production in reef communities. Unfortunately, as our understanding of corals and coral reefs increases, it becomes apparent that the effects of the human population on these communities may be increasing as well.