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This is Scientific Americans 60-Second Science. I'm Burling McCoy.

Mercury pollution from power plants and mining operations can end up in our air and water,

but it's tricky to predict just how much of that environmental mercury will make its way

into our food and our bodies. We were working on developing a bio-indicator, a bioscentenol,

that could inform us of the levels of mercury contamination across the US.

Ecologist Colin Eagle-Smith of the United States Geological Survey. He and his colleagues

came up with a practical way to determine the scope of mercury contamination in an ecosystem

by measuring mercury levels in a single species. Their bio-indicator, juvenile dragonflies,

or larvae. Dragonfly larvae stay under water, don't move much, are easy to collect and live

long enough to accumulate significant amounts of mercury. If you have enough locations sampled

with dragonflies and you can develop an index of the relative amount of mercury in the biological

community. The team measured mercury concentrations in thousands of dragonfly larvae collected

from waterways in 100 national parks during a 10-year period. And to amass the large sample number,

they recruited volunteers through the Dragonfly Mercury project. The volunteers used dip nets to

collect dragonfly larvae from their aquatic abodes. National park staff then sent the larvae

to laboratories for processing. For comparison, the researchers also measured mercury concentrations

...