Where are fringing reefs found?
Fringing reefs develop directly along a coastline or around an island, usually separated from land by only a narrow, shallow lagoon or no lagoon at all. Reef-building corals and coralline algae attach to hard, stable substrata in warm, clear, sunlit marine water. Their symbiotic dinoflagellates require light for photosynthesis, so active reef growth is concentrated in shallow water rather than the deep sea. A rocky coastal foundation provides attachment and resists wave disturbance, while proximity to land gives the reef its “fringing” geometry. Excessive sediment or freshwater runoff can inhibit coral growth, meaning not every nearshore rocky coast supports a reef. Barrier reefs lie farther offshore and are separated from land by a broad lagoon, whereas atolls form rings around a central lagoon, commonly after a volcanic island subsides. Polar waters are generally too cold and seasonally dark for tropical reef-building corals. Thus, “on rocky substrata near land” captures both the required attachment surface and the characteristic coastal position of a fringing reef, although carbonate reef frameworks themselves can later become the main substrate.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 2-3