Presenter: Derek Sowers (NOAA Ocean Exploration)

Description:
A strategically-planned multi-year exploration campaign on the Blake Plateau offshore of the southeastern U.S. has mapped what appears to be the most expansive cold-water coral (CWC) mound province thus far discovered. Bathymetric data from twenty multibeam sonar mapping surveys were synthesized and used to generate a standardized geomorphic classification of the region in order to delineate and quantify CWC mound habitats. CWC mounds in this region form distinct bumps or pinnacles (composed of slope, ridge, and peak features) readily observable in multibeam bathymetry data and were mapped in depth ranges spanning approximately 350-900 m. Seafloor terrain features were classified using the Bathymetry- and Reflectivity-based Estimator for Seafloor Segmentation (BRESS) method developed by Masetti et al. (2018) into five geomorphic landform classes (peaks, valleys, ridges, slopes, and flats) to support the enumeration of coral mound features and to quantify the area of each landform class. The “peak” landform class was utilized to identify and count the number of individual apparent CWC mounds. The complex geomorphology of eight subregions representing distinct spatial patterns of CWC mound formation was described qualitatively with geomorphic “fingerprints” and quantitatively by measurements of mound density and vertical relief. Ground-truth for the bathymetric analysis was provided by direct substrate observations from 23 submersible dive videos that revealed coral rubble to be the dominant substrate component within the peak, ridge, and slope landforms explored, thereby validating the interpretation of these bathymetric features as CWC mounds. The methods used in this study provide a pragmatic standardized approach for identifying, characterizing, and quantifying CWC mound-forming habitats and could be applied to other CWC provinces to enable more direct comparisons among geographically diverse settings.