Assessing the Impact of Long-term Mercury Contamination on Wildlife Health in New York, Using the Common Loon as a Sentinel Species

Dr. Nina Schoch1, Dr. David Evers1, Dr. Keith Grasman2 and Dr. Stephanie James3,

This study utilizes the common loon (Gavia immer) as a sentinel species for aquatic ecosystems to assess the effect of long-term mercury accumulation on wildlife health in New York’s Adirondack Park. Exposure of loons to mercury through atmospheric deposition and biomagnification is a concern throughout the upper Midwestern and Northeastern US and Canada due to depositional, geological, and pedological characteristics of the area. In the laboratory, mercury suppresses immune function in young loons. By evaluating the immune function of loons in relation to their mercury burden, this project will lead to an increased scientific knowledge of the (possibly synergistic) interactions between multiple stressors on the health of wildlife. Loons were captured using nightlighting and playback techniques. Blood samples were collected for evaluation of mercury levels, health parameters, and immune function. Birds were banded with USFWS bands and a unique color combination of plastic bands to facilitate subsequent observations to determine reproductive success and long-term survival/site fidelity. Loon immune function was measured by adapting in-vitro methods using cryopreserved lymphocytes. Lymphocytes were isolated using a slow spin technique that worked well for loons, although thrombocyte and heterophil contamination was higher than in other species. Lymphocyte samples were frozen in culture medium containing 10% DMSO. The samples were then thawed, and lymphocyte proliferation was induced via mitogens. Proliferation was assessed by an ELISA measuring the incorporation of Bromodeoxyuridine into newly synthesized DNA. These cryopreservation and cell culture methods will be used in future studies on the immunotoxicity of mercury in wild loons. The results of this project will address a primary data gap of how mercury interacts with other stressors by suppressing the immune system and increasing the susceptibility of birds to other stressors, thus contributing to an improved understanding of potential causes of population changes. In addition, this research will contribute to the management of wildlife populations and regulation of environmental pollutants by providing a direct measure of evaluating the risks contaminants pose to wildlife health. The results of this project will provide policy-makers with essential scientific information for making informed decisions about critical environmental protections, including monitoring and regulating emissions of anthropogenic pollutants, based on the health and reproductive impacts to common loons, a top piscivorous predator, and an iconic representative of freshwater ecosystems in North America.

1 BioDiversity Research Institute, Gorham, ME
2 Calvin College, Grand Rapids, MI,
3 Wildlife Conservation Society’s Global Health Program, Bronx, NY, Current affiliation is Pittsburgh Zoo, Pittsburgh, PA