By Beth Staples
Special to The Weekly
OLD TOWN — Old Town High School senior Andrew Brothers said the dragonfly larvae and zooplankton in teacher Ed Lindsey’s science lab are even more fun than the ant farm he had as a kid.
But the project that Brothers is working on is far from child’s play.
Brothers, along with senior Samantha Emerson and sophomores Christine Pollard and Jaime Lemery, is collaborating with University of Maine researcher Sarah Nelson, who is using dragonfly larvae as bio-sentinels for mercury in wetlands, stream watersheds, and lakes across the Northeast.
In their classroom laboratory, the students have set up mesocosms: mini-ecosystems in the form of tanks of circulated stream water from Baker Brook in Sunkhaze Meadows National Wildlife Refuge in Milford, along with 300 dragonfly eggs that were gathered from captured adult dragonflies.
Now that the eggs have hatched and the dragonfly larvae are eating, growing, and molting, the students are collecting data to find out how, and at what rate, mercury accumulates as the dragonfly larvae grow.
The students periodically measure mercury in the water, zooplankton, larvae, and the exoskeletons the young dragonflies shed. UMaine’s Sawyer Environmental Chemistry Research Lab will analyze the samples with a direct mercury analyzer. The goal is to shed light on the patterns of mercury accumulation as dragonflies grow from egg to adult.
In humans, low-grade chronic mercury exposure can impair cognitive functions and diminish motor skills, says Nelson. People are predominantly exposed to mercury, a heavy, toxic metal, from eating contaminated fish.
This is an independent study project for the high school students, who are pioneers of sorts for building the mini-ecosystems and raising dragonflies. Nelson said one of the only reference materials they could locate about the topic was a book written in the 1920s.
The dragonfly larvae are fed zooplankton the students grow in tanks of Baker Brook water. The zooplankton is raised on neon green phytoplankton, grown in an apparatus that Brothers built.
“They’re cool little creatures,” Brothers said of the zooplankton, which are barely visible to the naked eye. “They corral around like dogs to a food bowl when they’re being fed.”
The dragonfly larvae also are interesting. Lemery calls them “tenacious and mobile little soldiers” that sometimes escape from their containers. Each larva is housed in a separate container in the water tanks. Nelson said they would devour each other if they were kept together. It typically takes one to five years for a dragonfly egg to become an adult, she said.
The science students are mentored by Lindsey, one of 18 educators nationwide who received the 2012 Presidential Innovation Award. Lindsey, who teaches earth science and chemistry at Old Town High School, purchased equipment, including microscopes, with the award money he received. He described the research project as authentic and a public service.
Nelson is a scientist with UMaine’s Sen. George J. Mitchell Center for Environmental and Watershed Research and School of Forest Resources. Her research interests are watershed geochemistry, atmospheric deposition, and mercury.