Coral reefs protect coastlines by forcing incoming waves to break offshore and by slowing the remaining water across a rough, shallow surface. Less wave energy reaches beaches, buildings and coastal roads. The protection depends on reef height, width and physical complexity, which means living coral growth helps maintain a natural barrier that erosion continually wears…
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Fringing reefs, barrier reefs and atolls are the three main coral reef types in the classic geographic classification. The categories describe each reef’s position relative to land and the lagoon that may separate them. They also capture stages in a long interaction among coral growth, sea level and the movement or erosion of oceanic islands.…
A coral reef is made from a limestone framework built and modified by living organisms. Reef-building corals provide much of the architecture, but the finished structure also contains coralline algae, shells, broken skeletons and carbonate sand. Living tissue covers only the active surface of a reef that may contain the accumulated remains of countless earlier…
Corals are animals, even though a reef can resemble a garden made of branches, fans and rounded boulders. Each living coral is built from one polyp or a colony of many polyps, soft-bodied invertebrates related to sea anemones and jellyfish. Their fixed position and bright colors create the plantlike appearance, while a close look reveals…
