Scarborough students test mercury levels in Millbrook, Nonesuch

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SCARBOROUGH — Ninth-graders Evon Li and Sorenda Muth fell into the mud for science.

The two girls were part of a class trip into the Millbrook and Nonesuch watersheds to test the mercury levels of various animal and soil samples in the area. While they did find high levels of mercury in a few samples, the conclusion the class made was that there simply weren’t enough samples.

“We tried to cross a stream by walking on a fallen tree,” said Muth. “We fell in and got stuck in the mud.”

Despite the messy challenges, the class was able to collect 10 samples – seven dragonfly larvae and three clams – and send them to the University of Maine to be tested.

That was where Dr. Sarah Nelson came in. Nelson has been working with students all over Maine to teach them how to collect clean samples that can actually be used for scientific research. She works with interested teachers, explaining scientific process and what they can do with their classes to gather data for scientists.

“I teach them how the professional scientists do it, and show them how they can do real research in the classrooms,” Nelson said.

This is the second year freshman science teacher Emily Sherman has taken her class out to collect samples as part of the science curriculum at Scarborough High School.

“They study how toxins travel through water and accumulate through organisms,” Sherman said.

After studying the scientific process, the students developed hypotheses of the levels of mercury present in organisms from the two watersheds.

“I thought the dragonflies at Millbrook would have more mercury,” Gabby Christian said.

She said she developed that hypothesis based on the knowledge that there were more trees in Millbrook than Nonesuch.

“The leaves collect mercury,” she said.

Turns out, Christian was right. The average of the samples from Millbrook was 69.8 parts per billion, while the average of samples from Nonesuch was 31 parts per billion.

However, she was quick to point out that the range within their samples was large and that they should take more samples before coming to any conclusions.

Sherman said next year’s class would build on the findings of this year’s class.

“Next year’s students will review this data. That’s what scientists do — they build upon other researchers,” she said.

Nelson said the data she has received from Sherman’s class and other classes across the state has helped her with her research on bio-accumulation, or the process of mercury accumulating in larger and larger animals as it moves up the food chain to humans.

“I did a presentation of the students’ data at this year’s water conference,” Nelson said.

While mercury levels are too expensive for the students to test themselves, the partnership with the University of Maine allows the students to see the results of their research, something they would not be able to do by themselves.

“I think the bugs are a great indicator and that in a few years we’re going to be able to see patterns across the landscape,” Nelson said.

Emily Parkhurst can be reached at 781-3661 ext. 125 or

Sidebar Elements

Scarborough High School freshman Gabby Christian shows off her poster depicting the mercury levels of dragonfly larvae in the Millbrook and Nonesuch watersheds. Christian and other students tested clams, dragonflies and mud samples to determine if the levels of mercury in Scarborough’s watershed are dangerous.