When people see mild-mannered freshwater mussels (clams) in a river, they don't think of them as being heroic. However, for a second year the freshwater mussels that Genoa National Fish Hatchery has produced are protecting countless citizens against potentially harmful chemicals or environmental factors. The Environmental Protection Agency is testing Genoa NFH mussels in water that comes from Minnesota water-treatment plants that rely on surface-water sources. Mussels make ideal organisms to test river-water quality: They remain relatively immobile in aquatic systems; and in their quest for food, they filter large volumes of water, and possibly pollutants.

In 2007, Minneapolis Waterworks installed an EPA bio-monitoring system at its treatment plant in Minneapolis, Minn., using freshwater mussels to monitor raw water. The EPA system connects mussels that are receiving Mississippi River water from the treatment plant’s influent to sensors that send signals to a computer. If the mussels were to show coordinated shell-closure activity, an indication of poor water quality, the system would sound an alarm. Waterworks’ personnel would then further test the safety of the water.

This year Genoa NFH shipped 144 black sandshell mussels to St. Cloud, Minn., for the startup of two additional EPA bio-monitoring sites. The first is located at the St. Cloud Waterworks; the second, at the Excel energy plant in Sherburne County, Minn. Genoa NFH is one of a very few select mussel-culture facilities that can supply mussels greater than two inches in size, the size monitoring systems such as these require. With the addition of these two new monitoring sites, EPA is testing the mussels’ abilities to monitor water quality in more than 60 miles of the Upper Mississippi River.

So I ask, rocks with guts or superheroes in training?  You decide.