Atoll islands
Atoll islands are wave-built accumulations of gravel or sand that sit on top of coral reef platforms. The island sediments are derived from the breakdown of calcium-carbonate secreting organisms, such as corals, bivalves, gastropods and foraminifera, that dwell on the adjacent reef systems.
The existence of these islands is intrinsically linked to the reef ecology, as they rely on the reef’s production of sediments; however, the formation, maintenance and dynamics of atoll islands are primarily governed by physical processes involving water level, waves and currents.
Key hydrodynamic processes include: