by Harry Vogel, Executive Director, Loon Preservation Committee
of the Audubon Society of New Hampshire

Background

Methyl mercury is one of the most toxic and biologically active forms of mercury and is readily taken up by fish, loons, other wildlife, and humans. Significant exposure of wildlife to mercury is almost exclusively from the consumption of methyl mercury in fish. On many lakes in New Hampshire, fish mercury levels are higher than those thought to cause impaired reproduction in loons (Barr 1986).

With a diet that consists almost entirely of fish, loons are extremely valuable indicators of the health of our environment and the threat that elevated mercury poses. Because they are long-lived, high-trophic-level predators (McIntyre 1988), loons are at risk from mercury and other contaminants that bioaccumulate over time and biomagnify up the food chain. Individual loons and potentially entire breeding populations are impacted by elevated levels of mercury in the environment.

The Loon Preservation Committee, BioDiversity Research Institute, and other members of the Northeast Loon Study Working Group have conducted research over the past six years to determine the threat that mercury poses to loons in New Hampshire. This research has included collecting inviable loon eggs to determine causes of egg inviability and to measure mercury concentrations in eggs; capturing loons to sample mercury and other contaminants in feathers and blood; and sampling loons over successive years to determine the rate at which mercury is accumulating in loons.

New Hampshire Research Findings

Preliminary results of cooperative studies in New Hampshire and Maine have shown that loons with high mercury levels demonstrate abnormal behaviors that affect their abilities to defend a territory and raise young (Burgess et al. 1998; Nocera and Taylor 1998; Evers et al. 1999). Specifically, studies by the Loon Preservation Committee and other members of the Northeast Loon Study Working Group have revealed the following:

• 52% of 197 loon eggs tested in New Hampshire were found to have mercury concentrations over 0.5 parts per million (ppm), a level high enough to potentially affect reproductive success in birds (Thompson 1996; Evers et al. 1998a; Taylor and Vogel 1999).
• 18% of 135 adult loons sampled in New Hampshire were found to have blood mercury levels above 3 ppm, the established risk threshold for adults (Evers et al. 1998c).
• 53% fewer young were fledged from birds with blood levels above 3 ppm compared to below 3ppm (D. Evers pers. comm.);
• the highest mercury levels in loon eggs and blood ever discovered in the United States were found in New Hampshire (3.9 ppm egg, 8.1 ppm blood) (LPC/BRI).
• While individual loons in other states have maintained constant mercury levels over time, individual loons captured during successive years in New Hampshire and Maine have shown an average 9.6% yearly increase in mercury levels (D. Evers pers. comm.).

These findings suggest that mercury could be affecting the longevity and productivity of loons in New Hampshire. A population model jointly developed by the BioDiversity Research Institute in Maine and the Environmental Protection Agency demonstrates that mercury is a significant contributing factor in a decline in productivity for loons in New Hampshire. If the current trend is not reversed, it will result in negative population growth for loons, a threatened species in New Hampshire. In addition to loons, mercury poses a risk to other wildlife species that live in aquatic habitats or prey on fish, including mink, otter, Belted Kingfishers and Bald Eagles.

Concerns over Local Mercury Emissions

Concentrations of mercury in loon eggs and in adult loons, and the accumulation of mercury in individual loons over time, suggest that current levels of mercury emissions are high enough to pose a threat to loons and other wildlife in New Hampshire (Evers et al. 1998c). The United States Environmental Protection Agency=s Mercury Study Report to Congress (1997) indicates direct links between local mercury emissions and high levels of mercury in fish. Although mercury can be transported over long distances in the atmosphere, the majority of airborne mercury deposition is thought to be from local or regional sources (NESCAUM 1998). Therefore, a reduction in mercury from these sources would reduce the amount of mercury in New Hampshire=s environment, to the benefit of loons, other wildlife, and people.

LPC strongly supports any initiative to reduce mercury emissions into the atmosphere from point sources in New Hampshire.

Literature Cited

Barr, J. F. 1986. Population dynamics of the common loon (Gavia immer) associated with mercury-contaminated waters in northwestern Ontario. Can. Wildl. Serv. Occas. Pap. 56.

Burgess, N.M., D.C. Evers, J.D. Kaplan, M. Duggan, and J. J. Kerekes. 1998. Mercury and reproductive success of common loons breeding in the Maritimes. In N. Burgess et al. (ed.). Mercury in Atlantic Canada: A progress report. Environment Canada, Atlantic Region, Sackville, NB. 104-109.

Evers, D.C., P.S. Reaman, D. Major, B. Hanson and R. Poppenga. 1998a. AAssessing the risk of mercury in a breeding population of common loons in New England@ presented at the regional mercury conference in Fredericton, N.B.

Evers, D.C., J.D. Kaplan, W.M. Meyer, P.S. Reaman, A. Major, N. Burgess, and W.E. Braselton. 1998b. Geographic trends of mercury measured in Common Loon feathers and blood across North America. Environ. Tox. Chem. 17:173-183.

Evers, D.C., P.S. Reaman, O. Lane and B. Mower. 1998c. Determining mercury exposure in Maine's fish-eating birds. Report submitted to The Maine Outdoor Heritage Fund from BioDiversity Research Institute, Freeport, Maine and MEDEP, Augusta, ME.

Evers, D.C., P.S. Reaman, C. DeSorbo, and B. Mower. 1999. Assessing the effects of mercury in Maine's Common Loons. Submitted to MEDEP by BioDiversity Research Institute, Freeport, Maine.

McIntyre, J.W. 1988. The Common Loon: Spirit of Northern Lakes. University of Minnesota.

NESCAUM. 1998. Northeast states and eastern Canadian Provinces Mercury Study: A Framework for Action. NESCAUM/NEWMOA/NEIWPCC/EMAN.

Nocera, J.J. and P. Taylor. 1998. In situ behavioral response of common loons associated with elevated mercury (Hg) exposure. Conservation Ecology (online) 2(2): 10. http://www.consecol.org/vol2/iss2/art10

Taylor, K.M. and H.S. Vogel. 1999. Mercury exposure as measured through abandoned common loon eggs in New Hampshire, 1998. Report submitted to USFWS, Concord, NH by Loon Preservation Committee.

Thompson, D. R. 1996. Mercury in birds and terrestrial mammals. In Beyer, W.N., G.H. Heinz, and A.W. Redman-Norwood (eds.). Environmental contaminants in wildlife: interpreting tissue concentrations. Lewis Publ., Boca Raton, FL. 341-356.

USEPA (U.S. Environmental Protection Agency) 1997. Mercury study report to Congress. Vol. V: An ecological assessment of anthropogenic mercury emissions in the United States. USEPA- 452/R-97-003. Office of Air Quality Planning and Standards, Office of Research and Development, Washington, DC.