Effect of Methylated Mercury on the Diving Frequency of the Common Loon

• Brian Olsen

  Juniata College

  Author

• Dave Evers

  Juniata College

  Author

• Christopher DeSorbo

  Juniata College

  Author

Rising levels of atmospherically deposited mercury and its incorporation into aquatic food webs have long been a topic of concern for threatened populations of the common loon, Gavia immer, in the northeast. Although little is known about the effect of mercury on adult loon behavior, it has been shown that mercury inhibits heme production, and may affect the oxygen carrying capacity of loon blood. We examined the relationship between diving frequency and mercury concentration in common loons. We found a significant difference among the frequency of foraging dives in loons with different mercury burdens (H = 8.75, df = 3, p = 0.033) and a significant correlation between dive frequency and mercury level (r = 0.136, N = 249, p = 0.032). Additionally, the effect increased at higher concentrations (H = 7.48 df = 1, p = 0.006). This result prompts concern over contaminated loons' ability to forage for themselves and their offspring, especially in populations that are already stressed due to other anthropogenic disturbances.

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