Oil exposure has been associated with devastating infectious disease outbreaks in wild populations of fish. The links between these outbreaks and the oil exposure are circumstantial but they suggest an associated perturbation of fishes' immune systems. In Phase 1 of our research we validated the use of the flowcytometer as a high-throughput, sensitive method for evaluating fish immune cell profiles. We sampled oil-exposed alligator gar and killifish near Terrebonne Bay in August.
Using methods proposed in this study, we found that exposed killifish had higher numbers of phagocytes and lymphocytes in their spleens. These cells also appeared more activated than the same cells in control killifish, which had not been exposed to oil. These findings suggest the fishes immune system was responding to an immunological threat. We have also collected blood and tissue from off-shore red snapper.
Our proposed study will integrate immunology, physiology and toxicology in direct exposure trials that will evaluate how exposure to oil affects fish physiology and the functions of the immune system by evaluating immunological and physiological changes in alligator gar and Gulf killifish. The alligator gar and Gulf killifish will be experimentally exposed and evaluated for changes in blood ions (osmoregulation), changes in metabolites (metabolomic analysis), changes in abilities of leukocytes to clear pathogens (macrophage phagocytosis and killing and natural killer cell activity) and changes in liver enzymes that are associated with oil exposure over time. The changes that occur in the experimentally exposed fish will be related to our findings from the fish that had been exposed to the Macondo 252 oil spill. These data will provide experimental validation of inferred changes found in field samples.
This integrated study will evaluate the degree to which the cellular components of the immune system are perturbed by oil exposure and related physiological changes that will help us determine how this exposure may result in increased disease susceptibility. This research will be conducted with cooperation between the National Science Foundation RAPID Oil Response funding mechanism, the College of Veterinary Medicine and the Department of Wildlife, Fisheries and Aquaculture at Mississippi State University, University of Southern Mississippi Gulf Coast Research Laboratory, the National Oceanographic and Atmospheric Administration, Nicholls State University and the University of Alabama at Birmingham.