Coral reefs in Fatu Huku Island, Marquesas Archipelago, French Polynesia

Abstract Fatu Huku is an uninhabited coral reef island in the southeastern Marquesas Islands (9°26′10″S, 138°55′26″W), French Polynesia. The island is 1.3 km2, with a lagoon of 23.7 km2. The deepest part of the lagoon is measured at 36.6 m, while outer reefs recorded a deepest point of 114.7 m. Distinct geomorphic features identified from satellite imagery include passes, channels, single and triple barrier reefs, fringing reefs, ledge, and bulge. In 2016 a digital depth model constructed using water depths and video (R2=0.66 and r=0.81) was used to calibrate and validate four habitats: deep water, reef flat, coral reefs, and sand. The classification of habitats was implemented with a satisfactory overall accuracy of 0.75. The relationships between benthic habitats and morphometry (bathymetry, slope, hotspots, and ecotones) are discussed.