Determining Mercury Levels through Dragonfly Nymphs


Mercury (Hg), a natural element, is held within rocks. However, it is released into the atmosphere primarily through human activities, such as burning coal. Mercury is then carried by winds, eventually returning to the earth's surface by gravity or rain.

When Mercury is deposited or flows into wetlands, it is converted by bacteria into a toxin. Over time, this toxin bioaccumulates in animals, reaching potentially deadly levels in top predators.


How much mercury exists within our national parks? First, researchers from the University of Maine determined that aquatic dragonfly nymphs, the juvenile stage of adult dragonflies, contain mercury levels representative of their wetland environments. The researchers then collaborated with scientists at the National Park Service Air Resources Division to create a citizen science program investigating mercury levels in the national parks. National park units recruited volunteers, known as citizen scientists, to collect dragonfly nymphs for analysis.

Eighth grade students busy collecting data.

At Big Cypress National Preserve, 8th grade students from Seacrest County Day School searched the swamp for samples. During the winter of 2012, 27 dragonfly nymphs from three sites within Big Cypress were collected and sent to the University of Maine for analysis. On average, Big Cypress dragonfly nymphs did contain elevated levels of mercury compared to other parks.

Mercury concentrations were found to vary from one National Park Service unit to another, with eastern units generally containing higher mercury levels than western units. Data from some units revealed high variability within parks as well.

Seacrest students continued the study, returning for its second year. They collected 54 dragonfly nymphs from four sites across Big Cypress National Preserve during the winter of 2013. Results from 2014 samples are expected in the spring.



For a downloadable PDF of the summary of results, click here.

For an informative YouTube video about this fascinating project, please click here.

For teachers interested in incorporating mercury into their curriculums, please click here for resources.

Last updated: April 14, 2015

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