TATEM, S. A. *; DAUER, D. M.; Old Dominion University; Old Dominion University: Spatial and Trophic Relationships among Macrobenthic Species of an Intertidal Sand Flat

Our research explores the spatial and trophic dynamics of soft-sediment macrobenthic assemblages on a well-sorted intertidal sand flat laden with conspicuous enteropneust fecal mounds and sparsely clustered Spartina alterniflora near Beaufort, North Carolina. Species richness generally increased in enteropneust fecal mounds, with more species occupying the upper 1 to 3 cm of the sediment. The abundances of two dominant species, the haustoriid amphipod, Acanthohaustorius millsi Bousfield, and the paraonid polychaete, Paraonis fulgens (Levinsen), were greater around the periphery of fecal mounds and in fecal mounds, respectively. Carbon and nitrogen isotopic analyses demonstrated a predicted enrichment of isotopes from producers to top level macrobenthic consumers. Nitrogen isotopic ratios clearly separated consumers of various feeding strategies. Sediment organic matter, macroalgae, and Spartina, alone or in combination, were more important food sources for consumers than particulate organic matter from the water column. Sulfur isotopic ratios, which are not currently available, may illustrate a clearer picture between macrobenthic feeding strategies, their location in the sediments, and preferred food sources. Future endeavors will continue to focus on trophic input through gut content analyses of the dominant macrobenthic consumers on this sand flat.