Publication Date




Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PHD)


Marine Biology and Ecology (Marine)

Date of Defense


First Committee Member

Martin Grosell

Second Committee Member

M. Danielle McDonald

Third Committee Member

Elizabeth A. Babcock

Fourth Committee Member

Claire B. Paris-Limouzy

Fifth Committee Member

Andrew J. Esbaugh


The timing and location of the 2010 Deepwater Horizon (DWH) disaster within the Gulf of Mexico resulted in crude oil exposure of many commercially and ecologically important fish species, such as mahi-mahi (Coryphaena hippurus), during their sensitive early life stages (ELS). Mahi produce positively buoyant and rapidly developing embryos. Therefore, ELS mahi may be directly exposed to the cardiotoxic tricyclic PAHs dominating the oil slicks in surface waters for a significant portion of their developmental period. Further, these embryos are transparent and are likely also exposed to simultaneous stressors occurring in surface waters, known to act synergistically in the presence of oil, such as ultraviolet radiation and increased temperature. This dissertation fills knowledge gaps about the sublethal effects of crude oil exposure in developing fish by presenting data indicating that oil exposure affects numerous physiological processes such as oxygen consumption, nitrogenous waste excretion, cardiac function, energy utilization and buoyancy in ELS mahi. Impacts were exacerbated when mahi were exposed to multiple stressors at once, emphasizing the importance of including additional environmentally realistic stressors/variables in future toxicity tests. An unexpected finding of this dissertation was that mahi embryos exposed to specific stressors or combination of stressors displayed early onset of negative buoyancy, underscored by increased metabolic rates and subsequent reductions in energy stores. Moreover, once stressors were removed, some embryos exhibited recovery of positive buoyancy. The last 3 research chapters sought to gain further insight into this intriguing discovery. Results from these chapters provide information regarding the rearing conditions required to initiate premature onset of negative buoyancy, as well as the potential limitations and consequences of this response. Finally, results from Chapter 5 link laboratory endpoints to ecological impacts, by exploring how changes in specific gravity during development translate to different vertical distributions in nature.


Mahi-mahi; Buoyancy; Development; Toxicology; Deepwater Horizon

Available for download on Friday, December 04, 2020