An integrated approach to benthic habitat mapping using remote sensing and GIS: An example from the Hawaiian Islands

Abstract

This chapter documents our effort to map benthic habitats within the KalokoHonokohau National Historic Park, Hawai`i, USA. We produce detailed benthichabitat maps by using a combination of color aerial photography, high-resolution bathymetry, and georeferenced underwater video and still photography. We classify individual habitat polygons using five basic attributes and additional information regarding geology, morphology, and coral species. Derivative data sets including isobaths, hillshades, and slope maps are also generated. The mapping shows that benthic habitat and seafloor morphology varies greatly throughout the study area. Nearly 73% of the study area consists of a hardbottom structure that is potentially available for coral habitation; the remaining 27% includes unconsolidated sediment and artificial or historical features. Coral cover is generally low and increases with water depth. The offshore geology is predominantly composed of smooth to undulating pahoehoe-type basalt flows that form flat to gently sloping benches, vertical walls, and steep escarpments. In some locations the basalt surface is irregular and mounded into ridges, pinnacles, and arches. Large rounded basaltic boulders and smaller scattered rocks are common throughout the marine portions of the park. Coral or accreted carbonate reef obscures the underlying volcanic surface in only a few areas. The underlying geologic framework and morphology of the submerged volcanic flows within Kaloko-Honokohau National Historical Park provide the primary control on benthic habitats within the park. The habitat maps and associated data can be used as a stand-alone product or in a GIS to provide useful baseline information to scientists, managers and the general public.