NOAA Shallow-Water Benthic Habitats: Guam

Benthic habitat maps for the nearshore, shallow (< 30 m) coastal waters of the island of Guam. NOAA's National Centers for Coastal Ocean Science (NCCOS) produced these data to support coral reef research and management. Habitat regions were digitally identified using visual interpretation of orthorectified satellite imagery with a minimum mapping unit (MMU) of approximately 1 acre. Includes biological cover types, geomorphological structure types, and geographic zones.

Eighteen distinct and non-overlapping biological cover types were identified. Habitats or features that cover areas smaller than the minimal mapping unit of 1 acre were not considered. For example, uncolonized sand halos surrounding coral patch reefs are too small to be mapped independently. Cover type refers only to the predominant biological component colonizing the surface of the feature and does not address location (e.g., on the shelf or in the lagoon). The cover types are defined in a collapsible hierarchy ranging from eight major classes (live coral, seagrass, macroalgae, encrusting/coralline algae, turf algae, emergent vegetation, uncolonized, and unknown), combined with a density modifier representing the percentage of the predominant cover type (10%-<50% sparse, 50%-<90% patchy, 90%-100% continuous).

Similarly, 14 distinct and non-overlapping geomorphological structure types were identified. 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.

Lastly, 13 mutually exclusive geographic zones were identified from land to open water corresponding to typical insular shelf and coral reef geomorphology. These zones include: shoreline intertidal, vertical wall (none identified), lagoon, back reef, reef flat, reef crest, fore reef, bank/shelf, bank/shelf escarpment, channel, dredged (since this condition eliminates natural geomorphology), unknown, and land. Zone refers only to each benthic community's location and does not address substrate or cover types within. For example, the lagoon zone may include patch reefs, sand, and seagrass beds; however, these are considered structural elements that may or may not occur within the lagoon zone and therefore, are not used to define it.