Date of Award

5-2012

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biochemistry and Molecular Biology

Advisor

John Pierse Wise

Second Committee Member

Ah-Kau Ng

Third Committee Member

Amy J. Davidoff

Abstract

Marine metal pollution is a health concern for marine mammals. Marine pollutants that pose health risks to humans were also shown to produce adverse health effects in marine mammals. Although metals can be potent human toxicants they are not commonly studied in great whales. Chromium (Cr) is a metal present in the marine environment but rarely studied in marine mammals. A few studies reported Cr levels in marine mammal tissue but its toxicological effect was not addressed. Cr exists in the marine environment in its trivalent [Cr(III)] and hexavalent [Cr(VI)] forms. Naturally occurring Cr exist mostly as Cr(III), a less potent toxicant than Cr(VI). Cr(VI) is mainly a product of human activities. Studies in humans and animal models show that Cr(VI) cause several adverse effects in multiple biological systems. Cr(VI)-induced health effects include respiratory effects, decreased fertility, depressed immune system and cancer. Underlying these health effects are mechanisms of cellular toxicity, which include cytotoxicity and genotoxicity. The presence of Cr in the marine environment is therefore a potential health concern for marine organisms. Our study investigates Cr (Cr(VI) and Cr(III)) as potential health concerns for marine mammals focusing on great whales. We begin our study with the North Atlantic right whale, a baleen whale with a limited distribution off the eastern coast of North America. Then, we extend our study to the sperm whale, a toothed whale, with a global distribution. We assess and contextualize the toxicity of Cr in these species with two approaches. One approach, direct assessment, involves investigating Cr levels in whale tissue and the cytotoxic and genotoxic effects of Cr in cultured whale cells. The other approach, contextualization, involves comparing our results in whales with those seen in humans. Our results show that the right whale and sperm whale are exposed to environmental Cr, and that Cr compounds can induce cellular toxicity. Although with some differences, this cellular toxicity is comparable to what is observed in human cells. As a consequence Cr is indeed a potential health concern for the whales and possibly for other marine mammal species as well.

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