Emerita talpoida and Donax variabilis distribution throughout crescentic formations; Pea Island National Wildlife Refuge

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Pulley, Blaik
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Pea Island National Wildlife Refuge is a 13-mile stretch of shoreline located on the Outer Banks of North Carolina, 40 miles north of Cape Hatteras and directly south of Oregon Inlet. This Federal Navigation Channel is periodically dredged and sand is placed on the north end of the Pea Island beach. While the sediment nourishes the beach in a particularly sand-starved environment, it also alters the physical and ecological conditions. Most affected are invertebrates living in the swash, the most dominant being the mole crab (Emerita talpoida) and the coquina clam (Donax variabilis). These two species serve as a major food source for shorebirds on the island. It is especially important to protect this food resource on the federal Wildlife Refuge, which operates under a mandate to protect resources for migratory birds. For this research, beach cusps of various sizes were sampled to determine whether there is a correlation between invertebrate populations and the physical characteristics associated with these crescentic features. In small cusps (<50m), where the expected physical parameters for cusps were seen, a relationship between invertebrate abundance and cusp location did exist. For larger cusps, the expected physical parameters were not met, and a significant macrofaunal relationship was not always found. The results support the theory that a beach nourishment design using “disposal nodes” that incorporate and mimic natural crescentic features would be an ecologically appropriate method of sediment disposal. Such a method would minimize initial mortality, leave maximum populations intact to repopulate affected areas, and would also facilitate a faster population recovery.
Donax; Crabs; Beach nourishment; Pea Island National Wildlife Refuge (N.C.)