Coral reef islands and atolls. The reef face is the zone above the reef floor or the reef drop-off. This zone is often the reef's most diverse area. Coral and calcareous algae provide complex habitats and areas that offer protection, such as cracks and crevices. Invertebrates and epiphytic algae provide much of the food for other organisms. A common feature on this forereef zone is spur and groove formations that serve to transport sediment downslope. The reef flat is the sandy-bottomed flat, which can be behind the main reef, containing chunks of coral. This zone may border a lagoon and serve as
Réunion's coral reef for coral at Réunion is between 23 °C and 28 °C. Increased surface water temperature related to global warming can contribute to disease and bleaching of coral reefs, as is apparent on Réunion. Natural cyclones and anthropogenic disturbances such as urban development of catchment areas affect the reefs of Réunion. These ecological disturbances have led to an increase in coral reef nutrient levels via submarine groundwater discharge. Increased nutrient levels have resulted in the modification of flora and fauna in the benthic zone. The coral reef is a natural barrier that protects the coast from typhoons. The least vulnerable sectors