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Airborne element enters food chain
Herald Staff Writer
The methyl mercury is passed along to fish-eating animals such as raccoons and aquatic birds, said Kate Williams, an ecological analyst from the BioDiversity Research Institute in Gorham, Maine, who participated recently in an examination of songbirds for mercury in Mancos Canyon.
"Investigation in the Northeast and around the Great Lakes regarding mercury and its effect on wildlife indicates that mercury has (wildlife) population impacts," Williams said. "The common loon, a high-level predator, has been the subject of numerous studies that show how mercury has effected behavioral changes in the species.
"Adult loons become lethargic and so they fish less," Williams said. "Consequently they bring fewer fish to their chicks, which show less success in fledging. Loons and other aquatic birds also may show feather asymmetry, changes in brain chemistry and endocrine disruptions of reproductive hormones."
Songbird studies are more recent, but a theory gaining acceptance is that spiders are the link between mercury in aquatic life and songbirds, said Koren Nydick, director of the Mountain Studies Institute, based in Silverton. Spiders eat aquatic animals which have been contaminated with mercury and songbirds feed on spiders.
"Wetland-dependent songbirds were chosen for study - in addition to fish and crayfish - because research is showing that they accumulate methyl mercury," Nydick said. "It appears that they are accumulating methyl mercury from prey such as spiders that serve as a link between the aquatic and terrestrial food webs. This is why we collect samples of invertebrates, soil and dead foliage to analyze for mercury, too.
"Mesa Verde National Park may seem an unlikely spot to study the ecological effects of mercury," Nydick said. "But mercury concentrations in wet deposition there are among the highest in the United States."
The findings of the songbird study will help determine if a full-blown study of methyl mercury accumulation in wildlife is warranted, Nydick said.
In Southwest Colorado, five reservoirs - McPhee, Narriguinnep, Totten, Vallecito and Navajo - are posted with Colorado State Department of Public Health and Environment advisories to limit consumption of certain fish species because of high levels of mercury.
Seven reservoirs in northwest New Mexico also have fish
advisories.
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