The sea floor has been usefully subdivided into seven different biotopes. Each biotope is distinguished by the specific composition of the bottom sediments, their morphological character and variation, and by the relative abundance of living organisms. The characteristics of each of these biotopes follows.

The types of sediments derived from the major sediment contributors also reflect the physical environment. The sediment derived from the reef biotas is composed of fragments of the tests of Homotrema and coralline algae, gastropods and serpulids, while the central lagoon sediments are represented by fragments of Halimeda and infaunal bivalves.