IMPACT OF WATER MOTION ASSOCIATED WITH HURRICANES AND RECREATIONAL BOATING ON INTERTIDAL OYSTER REEFS

Dead margins, piles of disarticulated oyster shells up to 1 m above mean high water, are increasing in abundance on intertidal reefs of the eastern oyster Crassostrea virginica along major boating channels along the east coast of Florida. In Mosquito Lagoon, within Canaveral National Seashore, past and present research has documented significant changes to oyster reefs associated with intense recreational boating. In this study, we compared pre- and post-hurricane information for 3 attributes of intertidal oyster reefs to test the hypothesis that the multiple storms of 2004 (Hurricanes Charley, Frances and Jeanne) would have the same or greater impact as recreational boating on the movement of shells to create, change or destroy dead margins on oyster reefs, or disperse or damage oysters resulting in stress that might increase disease loads. Specifically, we recorded: (1) shape of reefs as measured in vertical profile, (2) prevalence and intensity of Perkensis marinus (Dermo), and (3) shell size as measured as mean shell height. Vertical profiles measured along identical transects both before (July 2004) and after (October 2004) on both impacted (with dead margins) and reference (without dead margins) reefs showed variable changes, but dead margins were neither created nor destroyed by the three hurricanes. The mean maximum height of the reefs based on the profiles was also not significantly changed. Twenty-five live oysters were collected from each of 6 impacted and 6 reference reefs to be measured for shell height and disease prevalence and intensity. Collections were made on 3 dates prior to and 1 date after the 3 hurricanes. Mean shell height (mm) showed a 10 mm decrease on all reefs after the storms. Disease prevalence (% oyster infected) did not change significantly. Comparison of disease intensities showed higher intensities prior to the hurricanes. Overall, our results suggest that humans and recreational boating activity have more impact on the development of dead margins on intertidal oyster reefs than repeated hurricanes.