Defense Date

4-28-2026

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Dorothy Ellen Renegar, Ph.D.

Second Advisor

Joana Figueiredo, Ph.D.

Third Advisor

Bernhard Riegl, Ph.D.

Keywords

Crude oil, aromatic hydrocarbons, coral reef, petroleum, cellular condition.

Abstract

Coral reefs are biologically diverse marine ecosystems that provide numerous goods and ecosystem services. These sessile organisms are vulnerable to anthropogenic impacts, habitat degradation, climate change, and pollution, particularly Petroleum hydrocarbon contamination. Previous research has characterized coral species' sensitivity to hydrocarbons, using a continuous passive dosing system, but the specific histological impacts of petroleum hydrocarbons remain underexplored. This study investigates the histological effects of three petroleum hydrocarbons, 1-methylnaphthalene, phenanthrene, and toluene, on six Atlantic scleractinian coral species: Acropora cervicornis, Porites astreoides, Porites divaricata, Solenastrea bournoni, Stephanocoenia intersepta, and Siderastrea siderea. Coral fragments were exposed to species-specific hydrocarbon concentrations, and effects were quantified using a histological analysis scoring rubric. The NOEC, LOEC, and 48 h EC50 were determined for each experimental group. Coral species were highly sensitive to toluene exposure, indicated by complete mortality at the highest concentrations. Stephanocoenia intersepta exhibited the greatest tolerance to toluene, reflective by the highest calculated 48 h EC50 value (EC50 = 92.5mg L-1). Acropora cervicornis, demonstrated the lowest sensitivity and the most severe histological response, mortality, when exposed to 1-methylnapthalene (EC50 = 3126 μg L-1). Porites astreoides showed the greatest resilience across all hydrocarbon exposures. Histological analysis revealed that coral species experience significant sub-lethal stress at lower hydrocarbon concentrations compared to the effects which are detectable through visual macroscopic assessment, and there is variability in species-specific sensitivity thresholds. These insights improve our understanding of oil spill impact assessments by integrating both macroscopic and microscopic responses, providing a more accurate understanding of coral stress beyond visual damage.

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