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Egg Mercury Levels Tied to Ice Cover

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Mercury isotopes in the flora and fauna of the Arctic may be linked to the amount of ice cover present, a team of scientists from the National Institute of Standards and Technology (NIST) announced last week.

An international research team studied seabird eggs to track pollutant trends and found a correlation between the latitude of the nesting murre and the type of mercury found in its eggs, the NIST said. Mercury levels have been documented in northern environments for 20 or so years, but this was the first time that tracking has involved analyzing mercury isotopes combined with an effect called “mass-independent fractionation,” or MIF, which measures the degree of which sunlight has broken down the mercury (in a process called photodegradation) into forms that can travel up the food chain from plankton to fish to seabirds to eggs.

For the study, Native Alaskans and biologists went out in field groups to collect the eggs of the murres, a bird that nests year-round in three coastal Alaskan regions. They then analyzed the mercury isotopes present. Eggs from the northernmost nesting areas, which are covered year-round with sea ice, showed a lower amount of mercury isotopes than did eggs from southern Alaska, where there is no ice cover, the NIST said.

“The mercury in eggs from nests near ice-free seas reflected significantly greater effects of mass-independent fractionation,” the press release said. “The researchers believe that ice prevents UV light from reaching the mercury, effectively suppressing photodegradation.”

The study was a joint effort between the NIST, the U.S. Fish and Wildlife Service, the U.S. Geological Survey and the Alaskan Bureau of Indian Affairs. Next on tap: The researchers will use the same system to differentiate the sources of mercury in coastal areas from those that originate in oceanic waters. The team will collect eggs along Alaska's Norton Sound, which receives runoff from the Yukon River (including high concentrations of cinnabar, the ore from which mercury is derived), and compare it to eggs from remote island colonies that are more influenced by atmospheric and oceanic mercury sources, the NIST said.

“With the potential for global warming to dramatically reduce Arctic sea ice in the future, the relationship between ice cover and distribution of mercury in the environment is obviously an important one to investigate further,” the NIST concluded.