Recovery of Oyster Reefs (Crassostrea Virginica) in a Gulf Estuary Following Disturbance by Two Hurricanes

During the summer and fall of 1985, two hurricanes struck the Apalachicola Bay system, a center for oyster (Crassostrea virginica) production in the northeast Gulf of Mexico. The first storm, Hurricane Elena, physically destroyed the major oyster-producing reefs in the Apalachicola estuary in early September (9/1/85). This disturbance was followed a month later by considerable accumulations of spat on those reefs most affected by the storm. The second hurricane, Kate, struck the bay in late November (11/21/85) and probably contributed to the natural mortality of young-of-the-year oysters. However, overall oyster biomass did not seem to be affected by Kate. Subsequent oyster growth was substantial with full recovery of the oyster stock noted within a 12-mo period. A detailed evaluation was made of the response of this important estuarine population to these disturbances. The timing and nature of the disturbances relative to the natural history of the oyster were crucial to the overall recovery pattern of the population. Hurricane Elena occurred at the end of the oyster spawning activity in 1985. Effects of the storm probably increased habitat availability and reduced direct competition and predation such that the oyster population benefited from the successful recruitment. The subsequent storm, Kate, coming after the spawning period, was not as destructive to oyster populations as Elena and could have even enhanced growth of the survivors. Hurricanes are common along the Gulf coast during the spawning period of the oysters; it appears that C. virginica is well adapted for such natural disturbances. The observed response of the Apalachicola oyster population to successive disturbances has significant meaning in terms of the long-term ecological stability of estuarine populations and the evolutionary aspects of such biological response to temporally unstable habitats. In this case, such populations can be viewed as highly resilient under even the most extreme conditions of physical instability. However, the exact biological response to temporally irregular disturbances is highly dependent on the timing of such events relative to the natural history of population in question.