Semester of Graduation

Spring 2025

Degree

Master of Science (MS)

Document Type

Thesis

Abstract

Oyster aquaculture is expanding in the northern Gulf of Mexico, but climate change may challenge the sustainability of this industry. Projected increases in the frequency and intensity of low salinity and low dissolved oxygen (DO) periods could impact the behavior, metabolism, growth, and survival of oysters. Characterizing how oyster behavior links to environmental stressors could help better identify thresholds in their tolerance and inform predictive tools for aquaculture professionals. In this research, the effect of separate and concomitant exposures to low salinity and DO on the behavioral response of oysters was examined in the lab. The impact of other environmental variables on oysters’ behavioral response to low salinity and DO was also characterized in situ. In the lab, a fully crossed experiment with two levels of salinity (20 or 3) and DO (~7.0 and < 2.0 mg L-1) was conducted on adult oysters equipped with high-frequency valve opening recorders. The results were analyzed through 3 stages: Before (5 days of holding oysters under controlled conditions), Transition (3 days of rapidly adjusting water parameters to selected treatments), and After (5 days of holding oysters under selected treatments). Oysters spent more time fully open under low DO in isolation, but less time under concurrent low salinity and DO. Low salinity and DO showed a synergistic effect on oyster survival, but low salinity was more hazardous than low DO. In the field, oysters were deployed in a southern Louisiana estuary during summer 2023 and winter 2024 (3 months each). Generalized linear mixed models were used to test if temperature or chlorophyll-a influenced behavior during periods of low salinity (< 5), low DO (< 2 mg L-1), suboptimal salinity (5–10), and suboptimal DO (2–4 mg L-1). For each behavioral indicator the effect of temperature and chlorophyll-a on behavior was highly variable based on interacting environmental conditions. As environmental conditions continue to shift under climate change, understanding how oysters behaviorally respond to stressful conditions and their interactions can provide valuable insight into eastern oysters’ resilience in the future and aid in restoration and aquaculture enterprises.

Date

1-11-2025

Committee Chair

Romain Lavaud

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