PCB Exposure And Channel Catfish: An Analysis Of Immune Response And PCB Dynamics In The Presence Of Food Deprivation

Open Access
Author:
Demario, Devin Anne
Graduate Program:
Wildlife and Fisheries Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 27, 2012
Committee Members:
  • Tyler Wagner, Thesis Advisor
Keywords:
  • catfish
  • fisheries
  • polychlorinated biphenyls
  • toxicology
  • fish
  • contaminants
  • environmental contaminant
  • environmental toxicant
  • bayesian analysis
  • fish health
  • innate immune function
Abstract:
Polychlorinated biphenyls (PCBs) have adverse health effects on organisms, including disruption of the immune, reproductive, endocrine, and nervous systems. Although banned in the United States in the late 1970s, PCBs are persistent in the environment due to their propensity to bioaccumulate, thus remaining a threat to environmental and human health. Even though PCBs have been extensively studied over the past several decades, there remains uncertainty regarding the dynamics of specific PCB congeners in aquatic organisms. Much of this uncertainty stems from earlier studies relying on measures of total PCBs to assess health effects instead of evaluating individual congener dynamics. To reduce this uncertainty, I performed an experiment to examine the effects of food deprivation on congener dynamics and immune function in channel catfish (Ictalurus punctatus). I exposed channel catfish to PCBs using a short-term dietary exposure until fish attained an approximate 5 ppm body burden. The PCB exposure period was followed by a 7 week food deprivation period. Total PCB (TPCB), homolog groups, and congener concentrations were quantified in whole body, fillet and liver tissue prior to the PCB exposure period and 4, and 7 weeks post-PCB exposure. Numerous biomarkers of immune function were assessed at these time points. Results from this research revealed that TPCB concentrations in fillet and whole body tissue decreased over the duration of the post-PCB exposure period and the rate of depuration was slightly less in fish that were food deprived. Further, whole body TPCB concentrations continued to decrease in both fed and food deprived fish after 4 weeks post-PCB exposure, whereas concentrations in fillet tissue remained stable from 4 weeks post-exposure to 7 weeks post-exposure. Results from the homolog analyses revealed similar patterns when compared to TPCB and provided evidence that PCB homolog groups did not appear to depurate from liver, fillet, or whole body tissues differentially after 7 weeks post-PCB exposure. Analysis of individual congeners over time also revealed little, to no, congener-specific activity in liver, fillet, or whole body tissues. Fish health assays showed that the environmentally relevant concentration of PCBs did affect mechanisms of innate immune function, specifically bactericidal activity, and affected the fish’s ability to respond chemically (i.e. cortisol production) to the presence of stress (i.e. food deprivation). Results from this study suggested that food deprivation had a large effect on the immune function of channel catfish, with PCB-exposed fish demonstrating a slight decrease in immune function immediately post PCB exposure. Further, PCB exposed fish showed an increase in innate immune function after being fed clean feed and control fish (i.e., not PCB exposure) that were deprived of food showed an appreciable decline in immune function. The bactericidal activity assay revealed the most definitive negative response to PCB exposure and could potentially be a more sensitive indicator of immune health compared to the other assays examined. Further, bactericidal activity also responded more definitively in response to the treatment of feed deprivation. Results from this research confirm that PCBs alone are indeed modulators of the immune and endocrine system in two-year old (sub-adult/adult) channel catfish and depurate non-preferentially from tissues at a slow rate directly after removal of exposure to the toxicant. This research further suggests that food deprivation is not an effective method to utilize when attempting to increase rates of PCB depuration in channel catfish, and may actually further enhance the toxicity by decreasing immune function. Management agencies should continue to monitor PCB concentrations in aquatic systems and consider PCB exposure as a potential factor influencing the overall health of a fishery. Furthermore, because channel catfish are well researched, have a relatively long lifespan, occupy the food chain as a benthic oriented predator, depurate PCBs (and potentially other organochlorines) slowly, and are non-migratory by nature, they could prove to be a valuable species for fisheries managers to utilize in long-term assessments of ecosystem health.