SPATIAL VARIATION IN PREDATION ON SPISULA SOLIDISSIMA ACROSS RECENT BARRIER-ISLAND ENVIRONMENTS, BEAUFORT, NORTH CAROLINA

Bivalve shells record diverse biotic interactions, including failed and successful predatory attacks by multiple groups of predators. Spatial variation in predation patterns can inform us about ecological changes related to environmental and anthropogenic differences across local ecosystems and help us to interpret predation patterns in the fossil record.

This study focuses on the Atlantic Surf Clam (Spisula solidissima) from shallow marine habitats of coastal North Carolina, a regionally abundant bivalve mollusk that is subject to predation by multiple predatory organisms. The project is based out of the Duke Marine Research Facilities (Beaufort, NC), which offers immediate access to a wide range of habitats within a typical barrier-island complex. Sites were chosen to allow for comparisons of protected vs. open water settings, shallow water vs. intermediate depth sites, sandy vs. muddy substrates, and fluctuating vs. stable salinity habitats. Also, the sampled sites vary in intensity of anthropogenic effects: Beaufort is unique in having, simultaneously, both federally protected lands and intense shipping and fishing industries.

To date, 30 sites have been dredged for live and dead macroinvertebrates. Shells of Spisula solidissima are abundant at many of those sites. Predatory traces are frequent and include gastropod drill holes, repair scars, and shell edge chippings. Initial data suggests size-selective drilling predation, as implied by a positive correlation between shell length and drillhole diameter. The frequency of predation traces varies across different environmental and anthropogenic settings. Consistent with other recent studies, these preliminary results suggest that predation traces may offer quantitative insights as to the influence of local environmental and anthropogenic conditions on the intensity and nature of biotic interactions.