SURVEY OF MOLLUSCAN FAUNA FROM THE OFFSHORE MID-ATLANTIC UNITED STATES

Although the ecology of estuarine mollusks has been examined in detail from Delaware to Chesapeake Bay, the geographic distribution of molluscan occurrences along the mid-Atlantic shelf has received little attention. Understanding offshore molluscan ecology may prove useful for quantifying and mapping sand resources for beach nourishment programs.

The goal of this study is to quantify relationships between substrate and molluscan ecology, including presence/absence and taxon abundance data. Twenty-four vibracores were sampled from offshore sites in New Jersey, Delaware, Maryland, and Virginia. Core lengths ranged from 1 – 6 m, and sampled water depths from about 6 m to 15 m. Core sampling varied according to the occurrence of molluscan specimens and typically totaled two to twelve samples per core. Samples were sieved to 0.0025 mm to quantify mud, sand, and gravel components. Taxon identification was based on apices, aperture shape, and ornamentation (for gastropods), and ornamentation and hinge structure (for bivalves). Non-parametric statistical tests were used to test for significant relationships between substrate and faunal occurrences and abundance.

Preliminary results suggest that substrate may influence the presence and absence of specific taxa, such as Ensis and Crepidula. Substrate may also affect taxon abundance, as seen with the distribution of sand and gravel relative to Spisula. Beach restoration is important for protecting life and property along the coastal communities of the mid-Atlantic region of the United States, as well as maintaining a healthy tourism economy. As the primary source of sand for replenishment is offshore, information on the ecology of these offshore mollusks can be useful in understanding these environments. By determining habitats specific mollusks prefer, the molluscan fauna of these vibracores may serve as an indicator of potential sand resources in the subsurface and aid in targeting resource areas.