Mapping essential fish ‘hardbottom’ habitat using sonar techniques: A local reef off Masonboro Island, North Carolina, USA

This study investigates an outcropping submarine reef, known as John Creek Hardbottom, located on the shoreface off Masonboro Island, North Carolina. The exposure is likely associated with the high-relief Pleistocene coquina calcarenite hardbottom reefs, which are prevalent off southeastern North Carolina. The reefs provide essential ecosystem services, which include habitat for a wide range of biological communities, in addition to acting as an important sand source for local beaches and providing substantial recreational fishing and diving opportunities. Due to their local importance, the National Oceanic and Atmospheric Administration (NOAA) has classified the reefs as Essential Fish Habitat (EFH). In this study, a range of different hydrographic survey techniques, including sidescan sonar and single-beam echosounding, were collected to produce a geo-referenced mosaic and bathymetric grid of the reef. The reef’s various morphological features are classified based on terminology from previous studies, and upon further examination, a new term for local hardbottom reef morphology, known as Importantly, John Creek’s unique morphology differs from other nearby hardbottoms, allowing this study to provide a wider understanding of local hardbottom characteristics. Due to their protected status, in addition to natural and anthropogenic threats they face, mapping and monitoring southeastern North Carolina’s reefs provides critical information for all stakeholders involved in sustainable coastal management decision-making.