The ecological role of the eastern oyster, Crassostrea virginica, with remarks on disease

Historical writings and the presence of pre-Colonial shell middens provide evidence that individual eastern oysters Crassostrea virginica (Gmelin, 1791) grew larger and formed more extensive reefs than they do under present-day conditions of harvesting, habitat destruction, and disease. Their diminished abundance has reduced their roles in providing hard substrate, in filtering the estuarine water column, and in affecting energy flow and nutrient flux. The poorly understood interactions among the abundant inhabitants of oyster assemblages have undoubtedly also been affected, although it is not clear how or by how much. The one important difference between the results of mortality from harvesting compared with mortality from disease may be that the shells of disease-stricken oysters remain on the oyster bar to continue to serve as substrate. There may be a connection between stress imposed by overfishing or habitat alteration and susceptibility of eastern oysters to disease.