Mercury Levels Greatest Among Marine Birds in Western North America

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Map showing blood-equivalent total mercury (THg) concentrations in birds across western North America using original data (n=27,629 individual samples). Map: Ackerman et. al, 2016.

Map showing blood-equivalent total mercury (THg) concentrations in birds across western North America using original data (n=27,629 individual samples). Map: Ackerman et. al, 2016.

We know that mercury often ends up in the seafood we like to eat, so eating too much of a good thing can turn out to be a bad thing. Mercury by-products in the water that leech into the marine life is something that we can’t always avoid, but other animals are beginning to be affected by mercury as well.

The USGS partnered with organizations in the United States and Canada to study birds in the western part of North America. They were able to identify areas that were mercury hotspots and then began to study the amount of mercury that can be found in birds living in these areas. Some birds in mercury rich areas had a high exposure to mercury, causing this chemical to accumulate in their bodies. This process is similar to that of fish, where the fish’s body has absorbed harmful levels of mercury that could potentially be ingested by humans.

This is the first study that has researched toxicity and mercury’s risk to birds as it specifically affects the tissues located in different bird’s bodies. The study researched the levels of mercury that can be toxic to birds and how much mercury stays in their systems when they are exposed to different levels of the chemical.

The study found that mercury levels depended on the birds’ locations, migratory habits, diet, species, and habitats, among other factors. There was a greater exposure to mercury in ocean and salt marsh habitats than there was in freshwater habitats or terrestrial habitats. Birds that had a diet of fish or marine plants were more likely to have a higher concentration of mercury in their bodies. Birds that consumed plants or seeds as their primary diet were less likely to have a high mercury concentration in their bodies.

Blood-equivalent total mercury concentrations in birds among habitats in western North America (n=27,629 individual samples; data shows least squares means ± standard errors). Graph: Ackerman et. al, 2016.

Blood-equivalent total mercury concentrations in birds among habitats in western North America (n=27,629 individual samples; data shows least squares means ± standard errors). Graph: Ackerman et. al, 2016.

The study created a new model by which to convert mercury toxicity levels into blood-equivalent mercury concentrations. The scientists involved in the study were able to identify four general toxicity levels, or benchmarks, that described the different concentrations of mercury in birds’ bodies. Researchers analyzed 30,000 samples from 225 different bird species in various habitats. The study was supported by 200 scientific publications that included 20,000 more samples over 176 different bird species.

The study’s goal was to see how mercury is impacting birds in the western part of North America, as birds are an important bio-indicator of the health of the environment around them.

More:

Ackerman, J.T., Eagles-Smith, C.A., Herzog, M.P., Hartman, C.A., Peterson, S.H., Evers, D.C., Jackson, A.K., Elliott, J.E., Vander Pol, S.S., Bryan, C.E., 2016, Avian mercury exposure and toxicological risk across western North America—A synthesis: Science of The Total Environment, doi: 10.1016/j.scitotenv.2016.03.071.

Mercury Found in Birds Across Western North America, USGS

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