Suprabenthic species distributions relative to small-scale bathymetric features along the Virginia coast, USA

Abstract

This investigation explored relationships between suprabenthic community composition and fine-scale differences among bathymetric features in the shallow ocean waters and the surf zone off an eastern North America barrier island. Suprabenthic sled collections from the surf to 4 km offshore of Assateague Island, Virginia in June of 2008 and 2009 provide the first detailed analysis of the suprabenthic community of the first 30 cm above the sea floor along the Atlantic coast of the United States. Multidimensional scaling (MDS) revealed discrete assemblages of suprabenthic fauna associated with specific bathymetric features (surf zone, inshore flat, an 11–13 m deep trough, and an adjacent ridge). Virtually all abundant taxa showed significantly different abundances between these four zones (ANOVA). The densities of key taxa between years differed, but their affinities for specific zones were evident in both years. The near-shore flat had the highest abundances of crab and fish larvae, suggesting that this area may serve an underappreciated role as nursery habitat for both estuarine and coastal ocean species. The trough was notable for its aggregations of large crustaceans, the mysid Neomysis americana and shrimp Crangon septemspinosa, that are probably an important link in benthopelagic trophic transfer from detritus to fishes. Compared to coastal collections from the eastern Atlantic, the subtidal suprabenthos collected at Assateague showed an unusually large variety and abundance of anomuran crustaceans and a paucity of gammarid amphipods.