What Is A Coral Reef?

A Coral reef looks just like perforated rock. However, its formation is not at all like that of rock. Coral formation is, in fact, the result of the architectural labors of many generations of tiny sea creatures—creatures that are related to the familiar jellyfish and the sea anemone. These creatures, called polyps, are jellylike, pliable, cylinder shaped. One end is anchored to the coral colony, the deserted homes of a previous generation. The other end is the creature's mouth that opens at night into a fringe of small tentacles that reach out and feed on the plankton that rise to the surface waters. Each polyp builds a protective covering around itself, a sort of individual apartment formed of calcium carbonate secreted by its own outer skin. During the day these polyps retire within their refuges.
With infinite numbers of these tiny architects at work side by side, building upward toward the sun, year after year, century after century, the reef took on it's modern look. Marine plants took root, seaweed became lodged, sponges and algae—all shared in some degree in cementing the framework together.