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
Coral reef fish fish species. Reef habitats are a sharp contrast to the open water habitats that make up the other 99% of the world oceans. However, loss and degradation of coral reef habitat, increasing pollution, and overfishing including the use of destructive fishing practices, are threatening the survival of the coral reefs and the associated reef fish. Coral reefs are the result of thousands of years of coevolution among algae, invertebrates and fish. They have become crowded and complex environments, and the fish have evolved many ingenious ways of surviving. Most fishes found on coral reefs are ray-finned fishes, known for the