Date of Completion


Embargo Period



environmental toxicology, polycyclic aromatic hydrocarbons, chemical dispersants, natural stressors, immunotoxicology, reproduction, development

Major Advisor

Sylvain De Guise

Associate Advisor

Milton Levin

Associate Advisor

Thijs Bosker

Associate Advisor

Robert J. Griffitt

Associate Advisor

Maria S. Sepúlveda

Field of Study



Doctor of Philosophy

Open Access

Open Access


The explosion of the Deepwater Horizon oil platform on April 20, 2010 initiated the release of 640 million liters of oil into the Gulf of Mexico (GOM). In efforts to prevent the oiling of coastlines, response officials applied nearly 7.5 million liters of the oil dispersant Corexit. Despite these efforts, oil reached over 2100 km of coastline along the northern GOM, including estuaries that serve as important habitats and nurseries. These estuaries are dynamic ecosystems, with constant fluctuations in salinity and dissolved oxygen. While it is well-established that oil is toxic to marine species, gaps remain in the understanding of how the impact of oil exposure may have been exacerbated by environmental (hypoxia and low salinity) and anthropogenic (oil dispersants) stressors. The impacts of oil and oil dispersants were investigated in an economically and ecologically important GOM invertebrate, the eastern oyster (Crassostrea virginica). Oysters were exposed to Corexit, oil, or dispersed oil to evaluate potential toxic effects on immunological (phagocytosis and respiratory burst) and physiological (feeding rate) endpoints. Exposure resulted in significant modulation of immune functions and feeding rates, and oysters were most sensitive to dispersed oil. The impacts of environmental stressors on the physiological responses to oil exposure were investigated in sheepshead minnows (Cyprinodon variegatus), small estuarine fish native to the GOM with tolerance for a wide range of environmental conditions. Adult sheepshead minnows were exposed to oil in three environmental scenarios: normoxic, hypoxic, and hypoxic with low salinity. Oil exposure reduced egg production and fertilization rate, but only when sheepshead minnows were exposed in hypoxic and hypoxic with low salinity scenarios. Parental exposure in the normoxic scenario resulted in developmental effects in F1 and F2 generations, demonstrating transgenerational effects. F1 developmental effects tended to be altered in the hypoxic and hypoxic with low salinity scenarios. The combination of reduced reproductive capacity and altered development could lead to long-term population level impacts for sheepshead minnow. These data suggest that oil spill risk assessments that fail to consider anthropogenic (chemical dispersants) and environmental stressors (hypoxia and salinity) may be underestimating risk to the health of eastern oysters and sheepshead minnows.

Available for download on Monday, December 30, 2019