MCC crew members process larvae samples in the field, led by Scientist-in-Park Campbell.
On a warm and clear morning, a dedicated team assembles at the Howe Lake trailhead in Glacier National Park: Montana Conservation Corps members, wilderness rangers, and a research scientist. As they methodically pack their gear—nets, life jackets, and coolers—they prepare to track down one of the park’s most unassuming yet scientifically valuable creatures. While small and easily overlooked, these inhabitants of Glacier’s pristine waters hold crucial clues about the health of the wilderness ecosystem.
Mercury contamination remains a significant environmental concern, even in protected wilderness areas. Scientists are using an innovative approach to track this persistent pollutant across America’s national parks, including here in Glacier National Park.
Nets are used to fish dragonfly larvae from shallow mud.
Primarily released through industrial emissions, mercury can travel long distances through the atmosphere before being deposited in aquatic ecosystems. Once there, it can be converted to methylmercury, a toxic form that accumulates in food webs and poses risks to wildlife and ecosystem health. Tracking mercury levels in a vast and wild area like Glacier is difficult, but scientists came up with a very clever sampling method: dragonfly larvae.
Dragonfly larvae spend several years developing underwater before emerging as adults. During this aquatic phase, they accumulate mercury from their environment and diet, making them effective sentinels of mercury contamination in the ecosystem and food web. Research has shown that about most of the mercury in dragonfly larvae exists as methylmercury, the form that is important to measure because it poses risks to other wildlife.
Larvae are sorted by family to make sure a diversity of species are sampled.
Recent studies at Glacier National Park have provided important insights into mercury patterns in mountain ecosystems. In 2022, researchers sampled three sites within the park, finding mercury concentrations that ranged from low to moderate risk levels. These variations help park managers identify areas of potential concern and track changes over time.
Several characteristics make dragonfly larvae particularly useful for mercury monitoring. The larvae don’t move much, so we can be confident they represent the mercury levels at the exact site they’re collected from. Larvae have a consistent position within the food web, so the data is easy to interpret. They live in a huge number of bodies of water across different ecosystems. Finally, they can be sampled with lightweight equipment that can be carried far into the wilderness and with minimal training.
Ranger Jenny identifying the species of a larvae.
Research at Glacier and other parks has demonstrated that mercury levels in dragonfly larvae vary with habitat type, local conditions, and environmental factors. These patterns help scientists understand how mercury moves through ecosystems and potentially impacts wildlife populations. Dragonfly larvae mercury sampling is also part of the park’s wilderness character monitoring, helping managers quantify the effects of atmospheric pollution far from its sources.
The project serves as an effective platform for public, and especially youth, participation in scientific research. This year, MCC crews spent multiple days collecting dragonflies from different sampling locations. They operated like a well-oiled machine, carefully handling the larvae to avoid contaminating the samples with their skin, identifying the different species, and meticulously labeling each sample with the data the lab will need to process it. The students precisely followed the instructions of Scientist-in-Park Campbell, who made sure the collection procedures were followed to a T.
The team included a Montana Conservation Corps crew, wilderness rangers, Glacier’s volunteer office, a research scientist, and GNPC staff.
Through systematic monitoring using dragonfly larvae, researchers can better track mercury contamination in protected areas and assess the effectiveness of emission reduction efforts. This work provides crucial data for protecting the wilderness and wildlife of the park, while engaging young people in experiencing its wonder.
Learn more about dragonfly mercury monitoring on the National Park Service website.
How can you help wilderness monitoring in Glacier?
This project and many other critical projects and programs would not be possible without your donations to the Glacier Conservancy.
Donate now to support important work like this in Glacier National Park!
