Heavy metal movers

February 12, 2013

Juvenile wood frogs emigrating from their birthplaces in vernal pools into the terrestrial ecosystem may transfer mercury they accumulated during larval development into the food web, according to a team of University of Maine researchers.

The team, led by U.S. Geological Survey and UMaine wildlife ecologist Cynthia Loftin, conducted its study at four short-hydroperiod (likely to dry by mid-June) seasonal woodland pools in Acadia National Park on Mount Desert Island, Maine.

The researchers found in the 1- to 2-week-old embryos were near or below detectable amounts, indicating that transfer of mercury from mother to eggs was absent or minimal. However, mercury accumulated rapidly in the 6- to 8-week-old tadpoles.

Mercury, a heavy, toxic metal, occurs naturally and is introduced into the environment by metal processing, coal burning and mining. People are exposed to mercury by eating contaminated fish and wildlife. Over time, low-grade in people can impact cognitive thinking and fine motor skills.

While concentrations of total mercury differed among the pools and were greatest in the unburned softwood-dominated setting, the levels increased in all pools throughout the season. The pools dried in June and refilled with September and October rain.

Wood frogs can travel some distance from their natal pools. During summer, fall and winter, they live in wetlands and on land. In the winter, they hibernate underneath leaf litter, and soil. They return to pools in the spring to mate.

For a better understanding of the transport of this contaminant from seasonal pools into the surrounding environment and potential for uptake into the terrestrial food web, future studies should focus on the ratio of total to methylmercury (produced by burning of fossil fuels) in embryos, tadpoles and juvenile frogs leaving natal ponds, according to the research team, writing in the journal Northeastern Naturalist.

Explore further: Mercury concentrations in fish respond quickly to increased deposition

Related Stories

U.N. seeks global pact to curb mercury

November 13, 2007

Worldwide government leaders meeting in Bangkok have been asked to step up efforts to develop an international agreement curbing mercury.

Engineered bacteria mop up mercury spills

August 12, 2011

Thousands of tonnes of toxic mercury are released into the environment every year. Much of this collects in sediment where it is converted into toxic methyl mercury, and enters the food chain ending up in the fish we eat. ...

Recommended for you

Can Paris pledges avert severe climate change?

November 26, 2015

More than 190 countries are meeting in Paris next week to create a durable framework for addressing climate change and to implement a process to reduce greenhouse gases over time. A key part of this agreement would be the ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.