In partial fulfillment of the requirements for the degree of

Master of Science in Biology

in the

School of Biological Sciences

Michon A. Shaw

Will defend his thesis

“Quantitative Analysis of Living Shoreline Stability Through Observed Behavioral Adaptations of Eastern Oysters (Crassostrea Virginica)”

Friday November 20th, 2026

2:00 pm

Kendeda Building Seminar Room 118

https://teams.microsoft.com/meet/2776873581776448?p=SOEiaPkbSMIazN8h6v

Thesis Advisor:

Dr. Marc J. Weissburg

School of Ocean Science & Engineering

Georgia Institute of Technology

Committee Members:

Dr. Joseph P. Montoya

School of Ocean Science & Engineering

Georgia Institute of Technology

Dr. Emily G. Weigel

School of Biological Sciences

Georgia Institute of Technology

Abstract:

Living shorelines are increasingly recognized as important forms of natural coastal infrastructure, providing shoreline stabilization, habitat complexity, and essential ecosystem services. Eastern oysters (Crassostrea virginica), as foundational ecosystem engineers, contribute to these functions through reef formation and water filtration. However, the ecological consequences of predator-induced behavioral adaptations in oysters, particularly their potential effects on filtration activity, remain insufficiently understood. This study investigated whether exposure to predator-associated chemical cues, specifically homarine and trigonelline, influences the filtration behavior of juvenile Eastern oysters. Using a 12-hour mesocosm experiment, juvenile oyster spat were exposed to four experimental treatments: high concentrations of predator chemical cues, low concentrations of predator chemical cues, no chemical cues, and a no-oyster control. The experiment consisted of six experimental blocks, with four replicates per treatment within each block. Chlorophyll-a concentrations were measured at the beginning and end of each trial to quantify chlorophyll depletion and estimate oyster clearance rates. A mixed-model analysis revealed no statistically significant effect of chemical treatment on the proportionate reduction of chlorophyll-a (F(3,87) = 1.60, p = 0.195), indicating insufficient evidence to conclude that predator-associated chemical cues significantly altered oyster filtration behavior under the experimental conditions. Although treatment differences were observed, oysters in the no-chemical treatment generally exhibited greater chlorophyll depletion, while the no-oyster control demonstrated minimal chlorophyll loss. Oyster size measurements also revealed no significant differences among experimental groups (F = 1.23, p = 0.297), suggesting that variation in juvenile spat size was unlikely to explain the observed treatment patterns. Despite the absence of statistically significant treatment effects, observed differences in filtration activity suggest that predator-associated chemical cues may influence oyster feeding behavior and warrant further investigation. These findings highlight the importance of examining non-consumptive predator effects when evaluating oyster physiology, ecological functioning, and the long-term performance of restored living shorelines.