Honors Theses

Date of Award

5-2026

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Marine and Environmental Science

Faculty Mentor

Charles Martin, Ph.D.

Advisor(s)

Amy Sprinkle, Ph.D., Sean Richards, Ph.D., and Abbey Hotard, Ph.D.

Abstract

Pharmaceutical contaminants are increasingly prevalent in aquatic environments, yet their sublethal effects on ecologically relevant behaviors remain poorly understood, particularly in estuarine systems. Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, are of particular concern due to the conserved role of serotonin in regulating behavior across vertebrates. Here, we investigated how acute exposure to environmentally relevant concentrations of fluoxetine influences anti-predator behavior in Gulf killifish (Fundulus grandis), a key estuarine fish commonly found in saltmarsh habitats. Killifish were exposed to control (0 ng/L), low (17.8 ng/L), and high (596 ng/L) fluoxetine concentrations and subsequently tested in the presence or absence of predator olfactory cues derived from red drum (Sciaenops ocellatus). Behavioral responses were quantified using an ecologically relevant metric: occupancy of structural refuge. Fluoxetine exposure at low concentrations significantly increased refuge use in response to predator cues, suggesting increased vigilance. Predator cue presence did not significantly influence structure use across treatments except in those with low fluoxetine exposure (ꞵ = 3.35, p< 0.05). These findings suggest that even short-term exposure to fluoxetine can alter anti-predator behaviors in estuarine fishes. Changes in refuge use and social behavior may have cascading effects on predator–prey interactions and energy flow in coastal ecosystems. Given the widespread occurrence of SSRIs in aquatic environments, these results highlight the importance of incorporating behavioral endpoints into ecological risk assessments of pharmaceutical contaminants.

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