Date of Award

Spring 2008

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Daniel M. Dauer

Committee Member

Fred C. Dobbs

Committee Member

Kent E. Carpenter

Call Number for Print

Special Collections LD4331.B46 T385 2008


Spatial and trophic interactions between macrofaunal species were studied in a high energy intertidal system during spring-summer low tides. Bioturbation by the enteropneust hemichordate, Balanoglossus aurantiacus (Girad), as evidenced by large fecal mounds, was a conspicuous feature on the sandflat Sediment characteristics were compared between ambient (non-fecal) and B. aurantiacus fecal mound types (fresh-oxidized, fresh-reduced, aged-oxidized, and aged-reduced). Fecal material was differentiated by age based on the presence or absence of mucus and the time of fecal deposition. The color of fecal material was used to assign oxidative state. Multiple isotopes (carbon, nitrogen, sulfur) were used to determine the origins and transformations of organic matter within the sandflat The spatial distribution of macrobenthic species and community diversity metrics were studied in relation to ambient sediments and fecal mound types, tidal direction-distance from fecal mounds, and depth distribution below the sediment surface relative to fecal mounds.

Fecal and ambient sediments were well-sorted medium-fine sands with low total organics, indicative of a high-energy, highly permeable intertidal system. Total organics were higher in fecal mounds relative to ambient sediments. Stable isotope data indicated that drifting macroalgae, local patches of Spartina alterniflora, and plant detritus from surrounding marshes were the most likely organic sources for non-carnivorous species, with no direct incorporation of carbon from ambient or fecal sediments by deposit-feeding consumers. Nitrogen isotopes separated expected trophic levels and sulfur isotopes differentiated oxidized and reduced feeding habitats for consumers. Density of the haustoriid amphipod, Acanthohaustorius millsi Bousfield, was negatively associated with B. aurantiacus defecation; whereas, the paraonid polychaete, Paraonis fulgens (Levinson), was unaffected by the fecal disturbance. Both A millsi and P. fulgens exploited the upper surface sediments more than subsurface sediments; however, each was observed within deep subsurface sediments. Both species may use fecal mounds as foraging habitat and also move to greater sediment depths to avoid the physical disturbance of defecation, the overcrowding of surface sediments, or to avoid desiccation during low tide. The high mobility of A millsi and P. fulgens may permit coexistence with large bioturbators in this high-energy intertidal habitat.


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