3D CHARACTERIZATION OF REEF-TOP FEATURES IN THE MESOPHOTIC ZONE OF THE NORTHERN GULF OF MEXICO

Coral reef morphology varies throughout the mesophotic zone of the Gulf of Mexico, exemplified by the diversity of geological origin, including paleo-shorelines, reef top ridges, salt domes, and drowned reefs. The purpose of this project is to report on the geologic features and implications for the distribution of sessile fauna for several positive bathymetric features characterized as reef tops between 65 - 85 m water depths at the head of Desoto Canyon south of Mobile, Alabama. The information gained from this analysis will aid in artificial reef designs for the Gulf of Mexico restoration following the Deepwater Horizon Oil Spill of 2010. Additionally, the diversity of such mesophotic ecosystems highlight the importance of proper habitat and resource management considering the geological substrate of a region has an important connection to biological diversity. In May and June of 2022, multibeam bathymetric and backscatter data were collected aboard the NOAA ship Ferdinand R. Hassler resulting in a substantial improvement in seafloor resolution compared to previous efforts in 2001. Measurements related to area, relief, volume, and geologic origin were documented for select reef top features in the mesophotic zone of the Gulf of Mexico. As part of the larger Open Ocean Restoration Project, imagery and side scan data will eventually be available from ROVs and AUVs, for ground truthing purposes. Standard operating procedures (SOPs) have been developed detailing the workflow process in ArcGIS Pro to best characterize measurements related to slope, concavity, rugosity and other metrics. Visualizations and characterization of the seafloor features were made with QPS Fledermaus and ArcGIS Pro. Metrics and classifications generated from this analysis will be used in ongoing biodiversity studies driven by impacts from the oil spill. Overall, we identify areas where constructive and destructive processes have produced unique landform features on the seafloor that host a diversity of habitats and organisms. Metrics quantifying the morphology of such landforms in this study are required to accurately reproduce coral reef ecosystems and produce truly scaled models necessary for restoration of these coral reef habitats.