Seasonal diversity and composition of epibenthic organisms on a North Carolina, USA continental shelf hard bottom

Subtidal marine hard bottoms are valuable habitats that support diverse epibenthic and fish communities. The degree to which hard bottom community structure varies spatially and temporally is not fully understood. Identifications of macroalgae and sessile invertebrates in scraped quadrats were done at three separate times (May, July, and September 2016) at three sites along the 5-mile ledge hard bottom in Onslow Bay, North Carolina. Spatial and temporal epibenthic community diversity and composition were measured. Diversity did not vary over time (p=0.065) or between sampling sites (p=0.130). There was, however, a change in community composition over time (p <0.003) and between two of the studied sites (p=0.012). Bottom water temperature might partially explain the observed temporal variation in composition, and site wide patchiness might explain the spatial variation in composition. These findings indicate that seasonal sampling of multiple sites is required to establish community baselines for these valuable habitats.