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The Deepwater Horizon oil spill (DHOS) was an unprecedented event causing the release of 4.9 million barrels of crude oil into the northern Gulf of Mexico on April 20th, 2010. This spill occurred at a depth of 1500 m approximately 66 km offshore. The unique nature of the spill caused potential exposure scenarios to major coastal regions of the Gulf of Mexico including wetland habitats, benthic reefs, the air-sea interface, and pelagic zones between the leaking wellhead and the coast. In the aftermath of large disasters such as the DHOS, the main question that is asked is, "What are the long term impacts to the natural resources and habitats affected?" One such resource, the economically and ecologically important filter-feeding species Gulf menhaden (Brevoortia patronus), was the primary species of concern in this dissertation. Menhaden play a key role in the transfer of energy up the food chain and serve as an important forage species for many secondary and tertiary consumers. It was hypothesized that Gulf menhaden exposed to crude oil will show lesions in the gills and heart representative of acute and chronic exposures, based on the time of collection and exposure scenario. Additional studies examined the role of particulates in the toxicity of crude oil, as well as comparative evaluation of the sensitivity of menhaden and differences in target organ/phenotype of fish species that inhabit similar habitats. We found that there was evidence of crude oil exposure to Gulf menhaden based on gill, stomach, and heart lesions in the years following the spill as well as an increase in whole fish tissue polycyclic aromatic hydrocarbon (PAH) concentrations relative to a reference sample. Particulates with strong PAH signatures were also found in the hearts of the collected fish; however, our additional studies show that penetration of particulate material into the vasculature of selected fish is not likely due solely to particle exposures. Gulf menhaden were also shown to be more sensitive to crude oil exposures than Florida pompano. In our experiments, craniofacial neuromast cells and olfactory lamellae were severely impaired in exposed Gulf menhaden while pompano displayed a much higher prevalence of secondary gill lamellar adhesion as a result of the exposures. This dissertation highlights the importance of evaluating different species for their sensitivity to crude oil, the lesions present in fish exposed to crude oil, and also presents data on the ability of particulates to cross epithelial barriers. These findings may be relevant to both industrial particulate matter and micro plastics within the aquatic environment. |
