Benthic faunal assemblages off the Delmarva Peninsula

Abstract

Based on 90 quantitative samples collected May and November 1973 the species composition, distribution and abundance of benthic invertebrates on the inner continental shelf off the Delmarva Peninsula (38 ° 23′N and 47 ° 15′W) were determined. A total of 149 species were identified. Thirty-five were found only in May and 65 only in November. In May the fauna consisted primarily of nearly equal numbers of polychaete and crustacean species with an increase in the number of polychaete species and a decrease in crustacean species in November. In May the polychaetes Goniadella gracilis and Lumbrineris acuta were co-dominants (Biological Index Value) while in November the archiannelid Polygordius sp. was strongly dominant. There was essentially no change in the number of deposit-feeding individuals from May to November. Even though the trophic structure remained unchanged, the species changed and the total number of individuals increased by 50% from May to November. The Delmarva assemblage was briefly compared to benthic assemblages closer to the Delaware Bay estuary. Comparison revealed the importance of estuaries and ridge and swale microtopography in influencing the distribution of the shelf fauna. It was concluded that the Delmarva assemblage belonged to a clean sand fauna which occurs throughout the inner continental shelf of the Middle Atlantic Bight. A number of species representing polychaetes, crustaceans, mollusks and echinoderms were proposed as characteristic sand fauna species.