As their name implies, fringing reefsgrow in a narrow band or fringe alongthe shore (Fig. 14.14). Occurring closeto land, they are especially vulnerable tosediment, freshwater runoff, and humandisturbance. Under the right conditions,however, fringing reefs can be impres-sive. In fact, the longest reef in the world(though not the one with the largestcoral area) is not the famous Great Bar-rier Reef in Australia but a fringing reef that runs some 4,000 km (2,500 mi)along the coast of the Red Sea. Part of the reason that this reef is so well devel-oped is that the climate is dry and thereare no streams to bring in sediment andfresh water. The typical structure of a fringingreef is shown in Figure 14.14. Depend-ing on the place, the shore may be steepand rocky or have mangroves or a beach. The reef itself consists of an inner
reef flat
and an outer
reef slope.
The reef flat is the widest part of the reef. It isshallow, sometimes exposed at low tide(Fig. 14.15), and slopes very gently to- ward the sea. Being closest to land, it isthe part of the reef most strongly af-fected by sediments and freshwaterrunoff. The bottom is primarily sand,mud, or coral rubble. There are someliving corals, but neither as many colonies nor as many different kinds ason the reef slope. Seaweeds, seagrasses,and soft corals may also occupy the reef flat, sometimes in dense beds