Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)


Virginia Institute of Marine Science


Aquaculture of the hard clam, Mercenaria mercenaria, has steadily increased in the United States over the past 25 years. In some areas, including along Virginia’s coast, this industry has grown to such a scale that aquaculture systems now exist as agroecosystems within coastal waters. Several features of these aquaculture systems, such as high clam densities and protective mesh netting, may modify the availability of habitat, food, and nutrients and may be expected to affect benthic and nektonic community structure. Few studies, however, have evaluated these effects. We conducted seasonal (May – September) sampling in a tidal tributary of Chesapeake Bay in three shallowwater habitat types – clam aquaculture, seagrass beds, and unvegetated bottom. Multiple trophic levels were sampled, including attached macroalgae, resident epibenthos, and mobile demersal and nektonic fishes and crustaceans. We compared biomass and abundance of trophic assemblages across the three habitat types. Trophic linkages were quantified through diet analyses of top predators. Results indicate that less-mobile communities showed more differentiation across the three site types. Assemblages supported by clam aquaculture and seagrass sites tend to be more similar to each other than they are to the assemblages at the unvegetated sites. Prey assemblages demonstrate a distinct shift, however, from May/July to September; during May/July the seagrass site supports the highest biomass and abundance of prey, but in September the clam aquaculture site supports the highest biomass and abundance of prey. This shift seems to correlate with the presence of structure (natural and man-made) within each site. Highly mobile top-predators show little preference among clam aquaculture, seagrass, and unvegetated sites. Diets of top predators do not exhibit a consistent pattern based on the site in which the individual was caught, but the diets of some species do correlate to the prey communities at a specific site. The added structure and organic matter deposition associated with clam aquaculture sites appear to create functional redundancy and temporal variability within Cherrystone Creek, potentially enhancing the stability of the creek system.



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