A Comparison of the Macrofaunal Communities Inhabiting a Crassostrea virginica Oyster Reef and Oyster Aquaculture Gear in Indian River Bay, Delaware

The eastern oyster (Crassostrea virginica) is a vital species in the estuaries of the mid-Atlantic United States. Whereas their filtering activity and biodeposition play an important role in the ecology of these systems, the reefs they form are one of the few sources of hard bottom habitat for fouling organisms and are the foundation of a rich biological community. This species has experienced drastic declines throughout the mid-Atlantic region in the last two centuries due to overfishing, habitat loss, and disease. Much interest and effort is now focused on restoring this important commercial and ecological resource. Whereas oyster reef restoration is central to the recovery of this species and the habitat it creates, oyster aquaculture can provide many of these same services albeit on a smaller scale. This is a two-part study, assessing the macrofaunal communities associated with subtidal modified rack and bag aquaculture, conducted over the summer and fall of 2006. The first part of this study compares the macro-epifaunal communities associated with two oyster habitats: a created oyster reef and oyster aquaculture cages. Both habitats were sampled with lift nets and compared using two-way ANOVAs between habitat and time. Secondly, we compared the sediment composition and macro-infaunal communities below the oyster cages with a nearby reference area of open sand/mud bottom. A significantly greater (P < 0.05) total abundance and species richness was found in the oyster cages, but significantly greater (P < 0.05) species evenness was found on the reef with species diversity similar between habitats. The sediments below the oyster cages showed a slight but significant (P < 0.05) reduction in it's silt/clay fraction. The results of this study show that, this method of oyster aquaculture supports additional populations of ecologically and economically important macrofauna compared with a created oyster reef. Furthermore this study demonstrates that off-bottom oyster aquaculture operations in the mid-Atlantic United States are a beneficial addition to host estuaries and associated natural communities.