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
Two Water Mills with an Open Sluice book on Ruisdael's mills and water mills Slive calls it "Two Undershot Water Mills with an Open Sluice". The Getty Museum calls it "Two Watermills and an Open Sluice" on their website, object number 82.PA.18. Two Water Mills with an Open Sluice Two Water Mills with an Open Sluice, also known as Two Watermills and an Open Sluice, Two Undershot Water Mills with an Open Sluice is a 1653 painting by the Dutch Golden Age painter Jacob van Ruisdael. It is in the collection of the Getty Museum in Los Angeles. The painting shows two working undershot water mills, with