Date of Award

2026

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Biological Sciences (MS)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Gordon Paterson

Committee Member 1

Jill Olin

Committee Member 2

Rupali Datta

Abstract

For Carcharhinid species such as the bull shark (Carcharhinus leucas), the maternal offloading of nutrients is essential for pup development and growth, however, significant amounts of OCs are also transferred. As a top predator in aquatic food webs, bull sharks can potentially bioaccumulate high concentrations of pollutants such as dichloro-diphenyl-trichloroethane (DDT) that biomagnify through aquatic food webs. These pollutants are also hydrophobic and fat soluble and therefore pose toxicity risks to developing young bull sharks. In this study, liver tissues collected from juvenile bull sharks inhabiting Florida’s coastal waters were analyzed for a suite of organochlorine pesticides (OCs) along with stable carbon (δ13C) and nitrogen (δ15N) isotopes to assess for possible maternal offloading effects. Older bull sharks had significantly higher overall average OC concentrations (4885 ng/g lipids) while also having the lowest average percentage of lipids (42 %). With increasing age there was a decline in most lipophilic OCs, like DDT and chlordane compounds, indicating possibly high maternal offloading of these compounds as the sharks age and grow. The youngest bull sharks (USS2-USS5) had greater variability in OC concentrations, as well as more enriched carbon (δ13C) stable isotopes that were different from older juveniles. Multivariate analysis of OC profiles ordinated younger sharks to be more similar to the oldest juveniles suggesting that OC burdens in juveniles were representative of maternal offloading. This study highlights the need to understand the effects of bioaccumulation and biomagnification of OCs in marine top predators, such as the bull shark. These results may contribute to predicting contaminant distribution patterns in other ecologically similar aquatic species.

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