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Citizen Scientists Study Mercury in Dragonfly Larvae

Dragonfly Icons show what is measured when sampling mercury from dragonfly flies. Water, dragonfly larvae, and sediment. After up to 5 years in the water, a dragonfly larvae emerges as an adult, leaving behind the “exuviae�, Acadia NP, Maine.  Photo courtesy of the SERC institute. Volunteers at Cape Cod NS, Massachusetts, collect dragonfly larvae at Ryder Pond. Photo by Ken Shea. Gomphid, the most common dragonfly larvae family collected. Photo courtesy of the University of Maine. A students searches for dragonfly larvae during the Bioblitz at Rocky Mountain NP, Colorado. Photo courtesy of the National Geographic Society.
Students, teachers, park visitors, "BioBlitz'ers," and other citizen scientists collect dragonfly larvae samples in national parks for mercury analysis.

Dragonfly larvae are currently being sampled for mercury levels in national parks. Mercury is a toxic pollutant that can harm human and wildlife health, threatening the natural resources the NPS is charged with protecting. The main source of human-caused mercury in remote national park environments is atmospheric deposition from coal-burning power plants.

The larval stage of the dragonfly lives in the water, and individuals are collected from river or lake bottoms with nets. Dragonflies spend most of their life in the larval form and eventually morph to the fast-flying aerial predator in the adult phase.

The "Dragonfly Mercury Project" (DMP) engages citizen scientists such as students and visitors in national parks to collect dragonfly larvae from distinct sampling sites. The samples are then sent to laboratories at the US Geological Survey or Dartmouth College for mercury analyses. The study connects people to parks and provides baseline data to better understand the spatial distribution of mercury contamination in national parks.

National parks from Alaska to Florida and Maine to Colorado participated in studies, starting in 2011. Data are available and results allow comparisons between parks. Sampling continued in 2017, and planning is in place for future years of the DMP. The final data will shed light on ecosystem health by characterizing the risk and potential transfer of mercury around food webs.

Participating national park units, 2017. (Click map to enlarge)

Why Dragonfly Larvae?

Diagram illustrating that levels of mercury increase in concentration along the food chain.
The toxic form of mercury, methylmercury, increases in concentration in the food chain.

Dragonfly larvae build-up higher levels of mercury than other types of water-dwelling insects for two reasons. First, they are predators that eat a lot of smaller insects and are relatively high in the food chain. Second, they live a long time in the larval stage (up to 7–9 years!), eating and accumulating mercury as they grow and develop.

Levels of mercury in dragonfly larvae are important to understand because dragonfly larvae are also a food source for many types of fish. Fish are higher on the food chain and accumulate even more mercury. Fish are then eaten by birds and mammals, including humans, posing an even greater risk to health. Fish are more difficult to sample, particularly because they can move faster and are much bigger than dragonfly larvae.

On-site with DMP 2015

Rocky Mountain National Park and Great Sand Dunes National Park & Preserve were featured as just two of over 50 parks that participated in the Dragonfly Mercury Project in 2015. Experience the DMP by watching this short video, the second episode of Outside Science (inside parks)!

For more information, or if interested in participating, contact us or phone Colleen Flanagan Pritz, Ecologist, at 303-969-2806.

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This project began as part of Acadia Learning, a collaboration with the Schoodic Institute at Acadia National Park, the University of Maine, and Maine Sea Grant. The project was funded in large part by the NOAA B–WET (Bay Watershed Education and Training) Program and the University of Maine through Faculty Research Funds and High End Instrumentation Research. Key personnel who are contributing include:

Last Updated: September 12, 2017