Abstract Summary
Papahānaumokuākea Marine National Monument (PMNM) is one of the largest protected marine conservation areas in the world. During NOAA’s 2017 Reef Assessment and Monitoring Program expedition to PMNM, Rapid Ecological Assessments (REAs) were conducted to survey fish, coral, and invertebrate abundance at 7 remote islands, shoals, and atolls. In addition to the REAs, the benthos was photographed in order to be reconstructed into 3D reef models. The goal of this research is to analyze REA and benthos characteristics in an effort to study reef complexity and ecosystem function. Utilizing Structure-from-Motion photogrammetry techniques, the photos taken from each transect were aligned using Agisoft software, generated into a point cloud of overlapping data, to ultimately produce a 3D and Digital Elevation Model (DEM) of the reef. The 3D model was flattened to a 2D orthograph, and then analyzed together with the DEM using ArcGIS software. Along the orthograph, arbitrary survey plots were drawn and processed for many different complexity parameters using the Benthic Terrain Modeler tool, such as slope, curvature, roughness, and rugosity of the reef. GIS processing of the 86 reefs surveyed across PMNM has been completed at 1 centimeter (cm) and 5cm resolutions. Additionally, orthographs were analyzed using CoralNet, an online annotation tool for classifying percent coral coverage by genus and morphology (ex. Branching Acropora), as well as percent algal, macro-fauna, and abiotic benthos coverage. Future goals of this ongoing research include GIS processing up to the 100cm resolution, as well as statistical analysis to investigate correlations between reef complexity and REA data.
