Doctor of Philosophy (PhD)


Biological Sciences

Document Type



Analysis of integrative physiological responses is a valuable approach to studying the biological impacts of natural and anthropogenic stressors in biota. By measuring fluctuations in multiple physiological characteristics, we are able to predict the impact that exogenous stressors may have on organismal health. Laboratory studies are useful in studying the effects of a single or multiple stressor interactions in a controlled environment, although field-based studies allow for the understanding of how fish are affected in situ, where multiple natural and anthropogenic stressors exist. Using laboratory and field-based experimental design, physiological indices of fish health were measured in fish exposed to natural and anthropogenic stressors in two unique incidences. First, controlled laboratory-based studies were performed where fish were exposed to larval freshwater mussels, a natural stressor found in North American freshwater environments. Unionid freshwater mussel larvae, called glochidia, must attach to a host fish in order to metamorphose into their juvenile state. This obligate stage in the unionid freshwater mussel life-cycle was found to cause a stress response in fish infected at high concentrations, where elevated cortisol in stressed fish was found to be coincident with an increase in glochidia metamorphosis to the juvenile stage. Second, both laboratory and field studies were conducted to understand the effects of the Deepwater Horizon oil spill on populations of Gulf killifish (Fundulus grandis) in oil-impacted areas in Louisiana, compared to reference sites in Louisiana, Mississippi, and Alabama. We show evidence of exposure to crude oil coincident with contamination from the Deepwater horizon oil spill in field-collected fish collected in 2010 and 2011 from oil-impacted sites, which had divergent gene and protein expression patterns compared to fish from unoiled locations. Further, controlled laboratory exposures of Gulf killifish embryos to field-collected sediments from oiled locations revealed that fish exposed to heavily oiled sediments as embryos had reduced cardiovascular defects, delayed hatching, reduced overall hatching success, pericardial edema, and were smaller at hatch. Together, these data suggest that fish were exposed to toxins in crude oil for two successive breading seasons, indicating, that contaminating oil from the Deepwater Horizon oil spill impacts organismal fitness, which may be predictive of long-term effects on Gulf killifish populations, and other biota that inhabit these areas, and also highlights the utility of combining laboratory and field-based techniques to predict the effects of natural and anthropogenic stressors on fish.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Galvez, Fernando