Graduate Theses and Dissertations (2019 - present)
Date of Award
8-2026
Document Type
Dissertation
Degree Name
Ph.D.
Department
Marine Sciences
Committee Chair
Delbert Lee Smee, Ph.D.
Abstract
Oyster reefs are foundation habitats that support biodiversity, stabilize shorelines, and sustain coastal economies across the Gulf of Mexico, yet they are some of the most severely impacted marine habitats globally. Early life stages represent a critical bottleneck for oyster populations, when juveniles face highly variable environmental extremes alongside high predation driven mortality. At the same time, oysters possess remarkable capacities for phenotypic plasticity that may buffer them against these pressures. Understanding how environmental stress, predator behavior, and early-life plasticity interact is essential for predicting reef resilience and improving restoration outcomes in a changing Gulf Coast. Successful reef restoration depends heavily on early-life survival, a stage when environmental extremes and predation pressure exert strong control over population trajectories. Because restoration programs rely on deployment of large numbers of hatchery-reared juveniles into dynamic estuarine environments, identifying the mechanisms that enhance or constrain resilience during this window is central to designing strategies that produce self-sustaining reefs. To evaluate how multiple pressures shape early-life performance, a series of complementary experiments examined the effects of predator cues, hypoxia exposure, and regional variation in predator tolerance on juvenile oysters and their primary predator, the oyster drill. Large-scale nursery trials demonstrated that predator-cue induction can be implemented at restoration scales and consistently increases juvenile survival across intertidal and subtidal reefs. A multi-stressor experiment showed that early-life hypoxia conditioning substantially improves resilience to later severe hypoxia, while predator-cue induction provides a modest delayed benefit; however, concurrent exposure to both stressors can generate antagonistic effects under prolonged low-oxygen conditions. Comparative assays of oyster drills from Texas, Louisiana, and Alabama revealed strong population-level differences in feeding and behavior under low salinity, indicating fine-scale local adaptation or environmentally mediated developmental divergence. Together, these results illustrate how predation, environmental pressure, and plasticity interact to shape early-life resilience in a coastal foundation species and highlight mechanisms that can be leveraged to strengthen restoration outcomes across the Gulf Coast.
Recommended Citation
Russell, Christa M., "Predation, Pressure, and Plasticity: Mechanisms of Resilience in Gulf Coast Oysters" (2026). Graduate Theses and Dissertations (2019 - present). 261.
https://jagworks.southalabama.edu/theses_diss/261
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