Researcher Uses Insects to Test Ecosystem Health

“We want to determine what happens when our streams and rivers are screwed up.”

Image Jeff Wesner USD researcher Jeff Wesner next to water tanks containing insects that offer clues about the ecosystem.

VERMILLION, S.D. -- Tucked away on a field just north of the University of South Dakota, 24 large water tanks hold tiny bugs that tell a story about what’s going on in the environment.

These so-called aquatic mesocosms were set up about a year ago by Jeff Wesner, Ph.D., assistant professor in USD's biology department, sustainability program and Missouri River Institute. The experiment was designed to study streams and rivers on a smaller scale.

Millions of insects are hidden beneath the water, all with one purpose: to sprout wings and find a mate. That process, called emergence, happens every day in rivers and lakes throughout the world. Wesner’s research largely focuses on capturing those emerging adults and determining what they suggest about the health of the aquatic ecosystem where they’ve spent most of their life.

“We want to determine what happens when our streams and rivers are screwed up,” Wesner said. “Most of what we study are insects. We use those insects to tell us how healthy the ecosystem is. What we’re trying to do is take what we know about all the things that happen in the water and combine those with the flux of bugs out of the water. When we say a stream is polluted, that means one thing for the stream and another for birds around it. So we try to understand how the ecosystems are connected.”

One of the major research interests is measuring how emerging insects respond to extinction or invasion of fishes like Asian carp, which are competitors and predators of juvenile aquatic insects. Another research emphasis is measuring the amount of nutrients and contaminants that these insects export from the water.

“We want to be able to scale up from these little manageable systems to understand how miles of a real river have been affected by fish invasion or pollution,” Wesner said. “Can what we learn here be used to predict what actually happens in a real system?”

Wesner’s work reveals intimate connections between the water and the land. Changes to aquatic ecosystems can cascade beyond the water-land boundary, a connection that was largely unstudied until about 15 years ago.

“These are little puzzles to solve, and I like solving puzzles,” Wesner said. “This has applied aspects because we’re going to know something about contamination in our water, but it’s also this really complex puzzle to solve and figure out if we know something about how the world works.”

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