Meeting Abstract
Over 40% of intertidal oyster reef coverage of the eastern oyster Crassostrea virginica has been lost in Canaveral National Seashore waters since 1943 (east coast of central Florida, encompassing much of the northern Indian River Lagoon). As all of the losses were in primary or secondary boating channels, both anecdotal and correlative data suggest that boat wakes have contributed to this decline. Here we present three important types of evidence to further suggest this is the case. First, we have tracked the movement of intertidal reefs once death begins on the seaward reef edges. Reefs in boating channels move toward shore at an average rate of 1 meter per year, while reef locations away from boat channels have remained stable over time. Second, we have collected data on the burial depth of oysters/oyster clusters in areas near and far from boat channels. Near channels, the depth ranged from 1 – 4 cm, while further from boat channels, oyster burial depth exceeded 20 cm. Third, to experimentally document that dead reefs can result from boat wakes, we ran controlled boat passes to determine what wake heights were generated at oyster reefs in the Park. These results were then utilized in experiments at Florida Institute of Technology’s wave tank to observe oyster movement and sediment erosion. Data was analyzed using model selection and regression analysis. We found that wake heights as small as 2 cm were capable of dislodging and moving oysters when the oysters are only buried in the sediment from 1- 4 cm. Combined, these results help explain when and how boat wakes can destroy intertidal oyster reefs, and, thus, can be used to implement boating policies which would contribute to conserving this important ecosystem engineer.
