Characterization of Shallow-Water Reef Habitats of the Northwest Hawaiian Islands using 3-Dimensional Reconstruction Techniques

This study quantifies the coral genera and coral conditions present in the Northwestern Hawaiian Islands using Geographic Information System (GIS) digitizing, and provides a comparative analysis of GIS data to traditional visual survey data. The ArcMap GIS program was used to digitize one meter by one meter photographs of the seafloor. The plots photographed were previously annotated in a visual field survey. Annotations from both the GIS and visual surveys include the sizes and counts of coral genera and visible coral conditions. Coral conditions include but are not limited to algal overgrowth, pigmentation responses, bleaching, and predation. Pairwise t-tests were used to compare the GIS data to the visual survey data. The GIS survey found significantly different quantities, sizes, and genera of coral colonies from the visual survey. These differences were significant in Montipora, Pocillopora, and Porites genera (p < 0.05), and not significant in Cyphastrea, Leptastrea, Pavona, and Psammocora genera (p>.05). There was also no significant difference in the quantity of conditions recorded between the GIS and visual surveys (p > 0.05). This study concludes that significantly different data is generated by the GIS and visual survey methods. Although further investigation into the relative shortcomings of each method is required, GIS can be a faster, more convenient, and more accurate method of benthic surveying than visual surveying. With a transition to GIS surveying, coral reefs can be monitored with a higher frequency and accuracy than traditional visual surveying methods.