Coral reefs are considered to be the most diverse and complex marine ecosystem on Earth. Yet well developed reefs grow under a restricted set of environmental parameters. Factors most significantly influencing coral growth and distribution include temperature, light, and nutrient levels.
Many scientists also recognize bank reefs and patch reefs as distinct reef types.
Still other scientists have put forth their own theories or developed their own classifications. Fringing reefs, barrier reefs, atolls, bank reefs, and patch reefs are described below. Some reefs found in the national marine sanctuaries fit obviously into one of these categories. In other cases, the classification scheme does not clearly apply. Fringing reefs closely follow shorelines at a short distance with at most a narrow, shallow lagoon between reef and land.