The objectives of this study are to determine the role that contaminants in Areas of Concern in the Great Lakes and adjacent areas with elevated persistent contaminants are having on the immunocompetence of lake trout (Salvelinus namaycush), a native top predator fish species and sentinel species for health of the oligotrophic upper Great Lakes.

Aquatic contaminants have been implicated in altering the physiology and biochemistry of Great Lakes fish. From studies on several vertebrate species, chemical contaminants are suspected of modulating immune system function via suppression and inhibition of immune competence, stimulation, and hypersensitivity, autoimmunity, and toxicity. At the population level, some immunobiologists hold that even rather modest immune suppression from contaminants contributes to severity of disease occurrence and ability to combat infection. Earlier studies by this research team* demonstrated that in vitro bioassays, adverse effects on normal programmed cell death (apoptosis) could be seen in thymocytes (T cells) of lake trout at concentrations representative of those to which lake trout are exposed in the Great Lakes, especially in an Area of Concern, Saginaw Bay. Two PBTs (persistent bioaccumulative toxics), mercury (total) and PCBs (80 congeners), were measured in whole fish and selected immune tissues of kidney, liver, and spleen. Comparison with toxicity benchmark values suggested that PCBs and Hg in older lake trout may present a risk of modulating selected immune system cells. Residues of not only these contaminants but of key metal species, organochlorine congeners, and emerging contaminants such as polybrominated fire retardants are needed to realistically put the risk in an environmental context of site specific levels in more highly contaminated Areas of Concern. Lake trout are exposed to these contaminants when in near shore areas. Further knowledge is needed regarding other immunological endpoints in lake trout and mechanistic explanations of other cell controlling factors impacting the response of immune cells. This knowledge can point to potential immunological impacts on human and wildlife consumers of fish containing these contaminants.

A research team of collaborators from the USGS Great Lakes Science Center; University of Michigan, School of Public Health, and Department of Biochemistry; and Ann Arbor VA Medical Center is conducting these investigations.