HCNSO Student Theses and Dissertations

Defense Date

4-30-2020

Document Type

Dissertation

Degree Name

Ph.D. Oceanography/Marine Biology

First Advisor

D. Abigail Renegar, Ph.D.

Second Advisor

Jose Lopez, Ph.D.

Third Advisor

Thomas Parkerton, Ph.D.

Fourth Advisor

Bernhard Riegl, Ph.D.

Abstract

Coral reefs are keystone coastal ecosystems that are at risk of exposure to petroleum hydrocarbons from a range of sources, including oil spill incidents and chronic runoff, and are usually one of the highest valued natural resources for protection in Net Environmental Benefit Analysis (NEBA)/Spill Impact Mitigation Assessment (SIMA) of response methods and environmental damage. Previous research evaluating hydrocarbon impacts to corals has resulted in no clear characterization of sensitivity, as work has generally focused on higher-level effects, compounded by significant variability in experimental methodology. This represents an important knowledge gap in oil spill preparedness and response as it relates to the potential impact of oil spills to the coral animal and its symbiotic zooxanthellae. This research was designed to address this gap, using a standardized toxicity testing protocol to evaluate effects of the petroleum/dispersant system the Atlantic shallow-water coral species Acropora cervicornis, Porites astreoides, Siderastera siderea, Stephanocoenia intersepta, and Solenastrea bournoni. The central objective of the Coral-Tox project was to provide lethal and sub-lethal endpoints of hydrocarbon exposure for five key Atlantic coral species in order to support effective decision-making and response should a spill occur near coral reefs.

The relative sensitivity of these scleractinian coral species to hydrocarbon exposure was assessed with 48-h assays using 1-methylnaphthalene, phenanthrene, and toluene, as well as non-dispersed and chemically dispersed MC252 crude oil. Effects were evaluated based on physical coral condition, mortality, photosynthetic efficiency, growth rate, and gene expression. While the threatened species A. cervicornis is the most sensitive of those tested, the acute endpoints for the single-compound tests, and the oil and chemically dispersed oil exposures indicated that corals are comparatively more resilient to narcotic chemical exposure than other coastal marine species, possibly due to the lipid-rich nature of coral tissue and their ability to secrete mucus. Typically, mortality is used to compare the effects of contaminants, but sublethal impacts are necessary for assessing impacts of petroleum spills in the environment, particularly when evaluating the relative effects of a spill to different ecosystem components included in a NEBA/SIMA. Gene expression results were used to evaluate effects of the contaminants at levels below the onset of observable physiological changes or lethality. Identifying impact pathways of hydrocarbon exposure to corals from the genomic to organismal levels provides a framework for the prediction of oil impacts on the coral animal, significantly improving model inputs to predict the effects of spill responses in coastal tropical environments.

Comments

GoMRI Agreement Number: G-231807

ORCID ID

0000-0002-0393-7216

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

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