Fourteen distinct and non-overlapping geomorphological structure types were identified that could be mapped by visual interpretation of the IKONOS imagery. Habitats or features that cover areas smaller than the MMU were not considered. For example, sand halos surrounding patch reefs are too small to be mapped independently. Structure refers only to predominate physical structural composition of the feature and does not address location (e.g., on the shelf or in the lagoon). The structure types are defined in a collapsible hierarchy ranging from four major classes (coral reef and hardbottom, unconsolidated sediment, other delineations, and unknown), to thirteen detailed classes (sand, mud, spur and groove, individual and aggregated patch reef, aggregate reef, scattered coral/rock in unconsolidated sediment, pavement, rock/boulder (volcanic and carbonate), reef rubble, pavement with sand channels, artificial, and unknown).
Sand
Coarse sediment typically found in areas exposed to currents or wave energy.
Mud
Fine sediment often associated with river discharge and build-up of organic material in areas sheltered from high-energy waves and currents.
Spur and Groove
Habitat having alternating sand and coral formations that are oriented perpendicular to the shore or bank/shelf escarpment. The coral formations (spurs) of this feature typically have a high vertical relief relative to pavement with sand channels (see below) and are separated from each other by 1-5 meters of sand or hardbottom (grooves), although the height and width of these elements may vary considerably. This habitat type typically occurs in the fore reef or bank/shelf escarpment zone.
Coral formations that are isolated from other coral reef formations by sand, seagrass, or other habitats and that have no organized structural axis relative to the contours of the shore or shelf edge.
Individual Patch Reef: Distinctive single patch reefs that are larger than or equal to the MMU.
Aggregate Patch Reefs: Clustered patch reefs that individually are too small (less than the MMU) or are too close together to map separately.
Aggregate Reef High relief lacking sand channels of spur and groove.
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Scattered Coral/Rock in Unconsolidated Sediment Primarily sand or seagrass bottom with scattered rocks or small, isolated coral heads that are too small to be delineated individually (i.e. smaller than individual patch reef).
PavementFlat, low-relief, solid carbonate rock with coverage of macroalgae, hard coral, zoanthids, and other sessile invertebrates that are dense enough to begin to obscure the underlying surface.
Rock/Boulder Solid carbonate blocks and/or boulders or volcanic rock.
Reef Rubble Dead, unstable coral rubble often colonized with filamentous or other macroalgae. This habitat often occurs landward of well developed reef formations in the reef crest or back reef zone.
Pavement with Sand Channels Habitats of pavement with alternating sand/surge channel formations that are oriented perpendicular to the shore or bank/shelf escarpment. The sand/surge channels of this feature have low vertical relief relative to spur and groove formations and are typically erosional in origin. This habitat type occurs in areas exposed to moderate wave surge such as the bank/shelf zone.
Artificial
Man-made habitats such as submerged wrecks, large piers, submerged portions of rip-rap jetties, and the shoreline of islands created from dredge spoil. Includes active and remnant fish ponds walled off from the open ocean along the shoreline, often along a reef crest.
Land
Terrestrial features above the spring high tide line.
Zone, Cover, and Structure uninterpretable due to turbidity, cloud cover, water depth, or other interference.
