Year

2011

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Arts in Biology (MA)

Department

Biology

First Advisor

Dr. James J. Gelsleichter

Second Advisor

Dr. Judy Ochrietor

Third Advisor

Doug Adams

Abstract

Many hydrophobic environmental pollutants have been shown to bioaccumulate and biomagnify at high levels in sharks due to their high liver lipid content, high trophic level, and life history characteristics. Studies have demonstrated that the levels of pollutants present in shark tissues can not only exceed the recommended levels for human consumption, but that, in some cases, they are also greater than the threshold for physiological effect in other aquatic species. However, few studies to date have investigated the biological effect of environmental exposure to contaminants in sharks. Therefore, the goal of this study was to investigate, through the use of biomarkers, if sharks are experiencing physiological effects due to exposure to 1) methylmercury (MeHg) and 2) polycyclic aromatic hydrocarbons (PAHs). The results of the first part of the study indicated that total mercury (THg) concentrations (μg/g w.w.) in Sphyrna tiburo muscle tissue were positively correlated with size of the animals, but that metallothionein (MT), a commonly used biomarker for toxic metal exposure, was not a valid biomarker for Hg exposure in this species, as no correlation between MT in muscle or liver and THg was found. The later portion of the study demonstrated that sharks off the coast of Alabama that were exposed to oil from the Deepwater Horizon oil spill (DHOS) in 2010 are exhibiting biochemical effects in the form of induced activity of the Phase I biotransformation enzyme, cytochrome P4501A1 (CYP1A1). Further research on the effects of both MeHg and PAH exposure in sharks should focus on the effects experienced by larger species and those at higher trophic levels, which are known to harbor higher levels of contaminants, and therefore be affected to a greater extent, than the species analyzed in this study (i.e. small species occupying lower trophic levels).

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