Graduation Year


Date of Submission


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts



Second Department

W.M. Keck Science Department

Reader 1

Branwen Williams

Reader 2

Letizia Marsili

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Rights Information

© 2023 Makenna C Mahrer


Polycyclic aromatic hydrocarbons (PAHs) are a specific class of persistent organic pollutants (POPs) heavily associated with crude oil, and pose genotoxic and physiological threats to marine life when released into the aquatic environment during a petroleum spill. This study seeks to understand the residual impacts of the 2018 Corsica oil spill on Puffinus yelkouan (Yelkouan Shearwater), a seabird endemic to the Mediterranean basin, using the species as a bioindicator for contamination in the region. Though classified by the IUCN Red List as ‘vulnerable,’ this species remains grossly understudied in present monitoring literature. This study made use of blood samples and excreta taken from live P. yelkouan specimens in three different Mediterranean sites (Tavolara, Montecristo, and Villasimius) six months following the original spill. HP-LC was performed to assess individual PAH levels in the blood, followed by an assay for erythrocyte nuclear abnormalities (ENA), white blood cell differential counts (H:L ratio), and a fluorometric reading of porphyrin levels. While carcinogenic PAH levels did not significantly differ between islands, collective values were notably much higher than reported values in existing literature. H:L ratios and total porphyrin levels were not indicative of long or short term stress levels. Lobed ENA values were notably higher than reported literature indices, particularly in the Tavolara region, suggesting some level of genotoxic stress may be present in the area. However, no significant relationship was observed between total carcinogenic PAHs and total ENAs, leading us to believe other contaminants are likely present. Evidence does not suggest lingering effects from the 2018 spill are still present in P. yelkouan, but contamination of the area from other sources remains likely and warrants further study. Collectively, these findings present a foundational understanding for the health of P. yelkouan in the region, in the hopes of contributing to further conservation efforts.