Teresa J. Newton 2004 <p><span>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.</span></p> application/pdf 10.3133/fs20043046 en U.S. Geological Survey Effects of ammonia on freshwater mussels in the St. Croix River reports