Scientists have found a novel way to trace the path of mercury in the environment — through dragonflies.
Mercury is a dangerous pollutant that accumulates in the bodies of animals. It can fall to the ground in raindrops or snowflakes or, in vapor form, stick to leaves that shower to the earth in autumn. Scientists often track it through fish, which are sensitive to mercury.
But dragonfly larvae, known as nymphs, are much easier to collect and can be found all over the world, even in deserts where fish are rare. They’re also very loyal to their creek, pond or wetland, so they reveal what’s happening right in their local area.
The Dragonfly Mercury Project, run by the U.S. Geological Survey and the National Park Service, recruits volunteers nationwide to collect dragonfly larvae from parks, wildlife refuges and other protected lands. Frozen larvae are sent to a research laboratory for testing. Scientists can tell how much mercury is in their tissues and also sleuth out how that mercury arrived in the ecosystem.
The project has gathered a decade’s worth of data from 150 national parks, including Grand Canyon, Zion and Death Valley. It’s involved an estimated 7,000 community volunteers.
The work has turned up some surprises, like high levels of mercury in arid regions of the Southwest. Deserts were long overlooked in mercury testing, and now it’s clear they need more attention. A day catching dragonflies can offer vital insights into the changing chemistry of the planet.
This Earth Note was written by Melissa Sevigny and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
