Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Robert J. Diaz

Committee Member

Mark W. Luckenbach


A shortage of shell resources for restoring reefs of the Eastern oyster, Crassostrea virginica, has led to widespread use of substitute materials. The effectiveness of such alternative substrates as habitat for reef-associated fauna other than oysters is largely unresolved. I investigated the habitat value of oyster shell, surf clam (Spisula solidissima) shell, and pelletized coal ash reefs for benthic and nektonic communities. Oyster recruitment, survival, and growth were monitored on reefs of oyster and surf clam shell near the mouth of Chesapeake Bay and York River, USA. Oyster shell supported greater oyster growth and survival and offered the highest degree of structural complexity. On the York River subtidal clam shell reef, the quality of substrate varied with reef elevation. Oysters were more abundant and larger at the reef base and less abundant and smaller on the crest. The availability of interstitial space and appropriate settlement surfaces likely accounts for observed differences in oyster abundance across reef systems. These patterns give further context to the importance of substrate selection in restoration activities. Invertebrate fauna associated with oyster shell, clam shell, and pelletized coal ash reefs were investigated. Diversity and production were greatest on oyster shell reef. Species richness was lowest on coal ash; however, total community abundance was significantly greater than on the other reef types. Clam shell reefs showed intermediate abundance and diversity patterns but had the lowest values for production. Nekton abundance, diversity, and community structure between reef types were measured. Data show differences in community structure across habitat types. Species richness was greatest on oyster shell and coal ash. Significant differences in nekton presence and abundance between oyster and clam shell reefs were detected. Clam shell reefs were similar in species composition and abundance to a beach habitat. These reef habitats are refuges, as demonstrated by the transient nekton species that dominated all habitats. Oyster shell and coal ash reefs served as habitat to many ecologically, commercially, and recreationally important species, providing food and shelter during juvenile life stages, and suggest reef habitats are of great importance as habitat to finfish communities.



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