This is sustainable. Complex ecosystem which supports species diversity. Habitats for many organisms. Diverse environment in relatively small area. Coral reefs contain 22 of the 23 animal phyla found on the planet.
Symbiotic relationships are common and add to the complexity of species interactions.
Act as wave barriers and protect shorelines. Types of reefs. In a fringing reef the coral projects from the rocky shore and the reef remains attached to the land. There is no lagoon between the reef and the land mass. The rocks provide a substrate upon which the coral larvae can settle and begin growth.