The St. Croix River contains a diverse and abundant group of freshwater mussels. The St. Croix is one of the few rivers in the Midwest not substantially affected by the invasion of the exotic zebra mussel, which encrusts and kills native freshwater mussels. Increased concentrations of ammonia in river sediments, however, poses a significant threat to mussels.

• Center Fact Sheets
  
  

Project page
Effects of Ammonia on Unionid Mussels: A Potential Threat to Their Biodiversity in the St. Croix National Scenic Riverway