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 Sea Islands and 1880s the islands were mined for guano but the absence of a reliable supply of fresh water prevented long-term habitation. The Coral Sea Islands became an Australian external territory in 1969 by the "Coral Sea Islands Act" (prior to that, the area was considered part of Queensland) and extended in 1997 to include Elizabeth Reef and Middleton Reef nearly 800 km further south, already in the Tasman Sea. The two latter reefs are much closer to Lord Howe Island, New South Wales, (about ) than to the southernmost island of the rest of the territory, Cato Island. The islands,