Dragonfly larvae are excellent indicators of mercury risk because they can live in the same place, underwater, for years, eating insects and even small fish. Once in water and in their prey, mercury can build up inside the larvae and give scientists insight into the health of the waters in which they live. The larvae are part of a food chain in their respective ecosystems and may be eaten by fish, passing along the mercury contamination, and those fish might be eaten by people, putting both humans and animals at risk. 

The Dragonfly Mercury Project (DMP) is a national-scale monitoring, research, education, and public engagement initiative. The project is currently (since 2020) managed by the National Park Service and U.S. Geological Survey, in collaboration with the Appalachian Mountain Club and Dartmouth College. The project began with students and teachers in Maine working with the University of Maine and Schoodic Institute at Acadia National Park. Over the past 10 years, the DMP assessed the mercury levels of more than 500 water bodies in more than 100 U.S. national parks and other federal, state, and local protected areas – including Lowell National Historical Park. The project engaged more than 5,000 public participants in collecting dragonfly larvae from national parks across the country to measure the amounts of mercury contamination, assess the potential risk to other animals, and evaluate how well efforts to reduce mercury (in the U.S. and internationally) are working.