Cooperative Fish and Wildlife Research Units Program: Maine
Education, Research and Technical Assistance for Managing Our Natural Resources

Mercury (Hg) contamination in the northeastern United States, including Acadia National Park (ANP), is well documented and continues to be a public health issue of great concern. Hg contamination of wild amphibians has received little attention despite mounting evidence and reports of worldwide population declines. Here we report total Hg and methyl Hg concentrations for water, sediment, and green frog and bullfrog tadpoles (~ 1 year of age) from ANP, Maine, USA. Average total Hg concentrations in green frog and bullfrog tadpoles were 25.1+1.5 and 19.1+0.8 Hg ng/g wet wt, respectively. Average total Hg was highest for green frog tadpoles sampled from the Schooner Head site, a small semi-permanent pond where Ranavirus was detected during the summer 2003 sampling period. Methyl Hg comprised 7.6-40% of the total Hg in tadpole tissue (wet wt. basis), and average total Hg levels in tadpoles were significantly different (P < 0.05) among pond sites (n = 9). Total Hg in pond water was a significant predictor of tadpole total Hg levels (P < 0.05). Dissolved organic carbon was a significant predictor of both total Hg (P < 0.05) and Methyl Hg (P < 0.05) in water, and total Hg in water was also strongly correlated with Methyl Hg in water (P < 0.05). The methylation efficiency (ME) rates defined as total Hg:Methyl Hg ratio in pond waters sampled at ANP were higher than the reported ME for national parks located in the western region of the United States. Of the 9 ponds we sampled at ANP, 44% had ME greater than 10% suggesting that wetland food webs in the park are likely susceptible to high levels of total Hg bioaccumulation. These findings may be important to National Park Service resource managers especially considering the Class I airshed status of ANP and the strong potential for negative effects to aquatic ecosystem structure and function from Hg pollution.