Behold the unassuming mussel. Freshwater mussels move along in Minnesota rivers, not too fast, sometimes burrowing down into the sand. They siphon in nutrients from the water around them. Their larvae attach to fish as parasites, dropping off weeks later, sinking to the bottom to begin an independent life. Mussels can live for decades, even a century.

Mussels also serve as the aquatic equivalent of the canary in the coal mine, “clamming up,” if they detect contaminants in their watery homes. In fact, the City of Minneapolis places mussels near the intake for city water as a sort of early warning system.

Brooke Hunter ’17 (Stillwater, Minn.) and Lea Davidson ’18 (Walla Walla, Wash.) spent the summer at the University of Minnesota’s St. Anthony Falls Lab on the Mississippi River as part of a team studying how these critical stream-team members fare under conditions of flood or increased sediment load.

Although the mussels you eat are almost certainly marine mussels, freshwater mussels play an important role in the lives of fish, acting as biofilters, feeding on bacteria and algae, effectively cleaning the rivers they inhabit.

Investigating mussels’ response to changes in their environment was a team including Davidson, Hunter, Mac professors Kelly MacGregor, a geomorphologist; Dan Hornbach, an aquatic ecologist; biology staffer Mark Hove, two National Science Foundation student grantees, and researchers from the University of Minnesota.

Mussels were collected from the Mississippi River by scuba diving. Their shells were painted for ease of identification and they were placed in a stream where they could be monitored, often by Hunter or Davidson lying balanced on a plank above the stream. Other measurements were made in the indoor portion of the lab, where mussels were tagged with ‘gape’ sensors. Open shells generally mean a happy mussel; closed, increased stress.

What researchers learn about the stress levels of mussels has implications for river health, land use practices, buffer strips on farms, and—most important to Minnesota anglers—the lives of fish.

October 10 2016

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