Evaluating the Inducible Defense Morphology of the Eastern Oyster, Crassostrea Virginica, and Its Potential Applications for Oyster Reef Restoration
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Roney, Sarah Hope
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Abstract
The eastern oyster, Crassostrea virginica, is a critically important ecosystem engineer that provides habitat for numerous estuarine species, improves water quality, sequesters carbon, buffers shorelines, and provides many other ecosystem services. These oysters are also a basal prey resource for numerous estuarine predators, providing an important food source. However, due to overharvesting, disease, and other damage, oysters have experienced a significant decline in global abundance. Oysters exhibit an inducible defense, where juveniles (spat) grow stronger shells when exposed to predator chemical cues over the course of several weeks. The use of predator-induced, strengthened oysters in restoration practices could increase the survival of oyster spat, improving the success of oyster restoration outcomes, especially in areas experiencing intense predation pressure or limited by wild spat abundance. In this dissertation, I evaluate the potential for using oysters’ inducible defense to improve oyster restoration outcomes. First, I experimentally determined that oyster spat strengthen their shells in response to the chemical cues homarine and trigonelline, components of blue crab urine. I then examined the microstructure of oyster spat shells to determine what mechanism spat use to strengthen their shells, finding that spat use increases to both shell thickness and hardness, depending on age. Next, I determined the efficacy of using strengthened oyster spat in natural reef settings. I found that induced oysters experience a higher probability of survival and survive longer periods of time on natural oyster reefs and in diverse physical environments. In relatively high energetic environments, oyster reefs constructed as living shorelines were highly effective at reducing wave energy, suggesting that the use of induced oysters in these environments could increase spat survival on reefs and decrease erosion-causing waves, benefiting the ecosystem in multiple ways. These results suggest that the use of oysters’ natural predator defenses in restoration efforts has excellent potential to significantly improve oyster restoration success. Furthermore, with strategic decision-making on placement and design, oyster reef restoration efforts could restore ecosystem services in conjunction with shoreline buffering capabilities.
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2025-04-24
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Dissertation