Reef Morphology and Invertebrate Distribution at Continental Shelf Edge Reefs in the South Atlantic Bight

Abstract

Video footage recorded from 14 submersible dives on the continental shelf edge was used to describe and categorize reef morphology and quantify density and number of morphotypes of large sponges and corals. Significant variation in number of morphotypes and density of three dominant species among temperature classes, depth classes, and reef morphology categories was tested using a multiple response permutation procedure. The greatest densities of Ircinia campana, Stichopathes sp., and Muricea pendula, and the largest numbers of morphotypes were found between 18.1 and 21.0 °C and at depths between 51.0 and 60.9 m. Among reef morphology types, those that contained unconsolidated sediments such as “sand” and “large boulders with sand” exhibited the lowest densities and richness of morphotypes, while “block-shaped boulders,” “buried block-shaped boulders,” and “low-relief bioeroded” reefs had the greatest densities and largest numbers of coral and sponge morphotypes. Rocky reefs along the shelf edge with rough texture, complexity, and relief provide favorable conditions for epibenthic invertebrates. The warming and stabilizing effect of the Gulf Stream along the continental shelf edge allows some sessile macrofauna to inhabit deeper waters and more northern latitudes.