Semester of Graduation

Fall 2025

Degree

Master of Science (MS)

Department

Biological Sciences

Document Type

Thesis

Abstract

Photo-oxidation of spilled crude oil generates polar compounds that can heighten toxicity to marine fish embryos. We investigated the effects of photo-oxidized crude oil on early life stages of Gulf killifish (Fundulus grandis) by exposing embryos under flow-through conditions to water-accommodated fractions of four oil treatments: fresh oil unexposed to either sunlight or weathering referred to as dark control (DC), a UV-light oxidized whole oil (LT), the polar fraction extracted from LT (Pol) and the remnants after extracting the Pol from LT (NP). Oil loadings of 0.38–3.00 g oil/kg water were tested. Total PAH concentrations and chemical profiles of WAFs were determined via SPME-GC/MS, and embryo hatch success, heart rate, developmental abnormalities, and survival were monitored. Photo-oxidized WAFs (Pol and LT) yielded higher dissolved ΣPAH concentrations than non-oxidized oils (up to 4 times higher at 3 g/kg) after normalizing to carbon, although a Kruskal–Wallis test indicated no significant difference in ΣPAH among oil types at six hours after dilutions (p > 0.25). Compositionally, Pol and LT WAFs were overwhelmingly dominated by oxygenated fluorenone derivatives (~95% of ΣPAH), whereas DC and NP WAFs contained mostly low molecular weight parent PAHs such as alkyl naphthalenes. Hatch success remained high (89–100%) in DC, NP, and LT exposures, but was significantly reduced in the 3g/kg Pol fraction (84%) compared to 98% in controls). This indicated that polar photoproducts primarily drove hatching failure. No significant effects on embryo survival, hatch rate or heart rate were observed in any oil treatment. However, embryos in the LT and Pol groups exhibited more frequent sublethal cardiotoxic effects and developmental abnormalities (e.g., pericardial edema, unlooped heart tube) than those in DC or NP. These findings demonstrate that UV-driven oxidation substantially alters the toxicity profile of crude oil by enriching PAHs that impair fish embryo development. The effects of photo-oxidation should therefore be incorporated into future environmental risk assessment studies.

Date

11-18-2025

Committee Chair

Michael Hellberg

Additional Files
Charles Campbell Defense Results.pdf (371 kB)
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Charles Campbell Defense Results.pdf (371 kB)

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