As an aquatic ecologist, Professor Hornbach’s research focuses on the factors that influence the distribution and abundance of organisms in river systems. He has focused his research on a group of highly endangered animals, freshwater mussels. Over 70% of mussel species in North America are considered extinct, imperiled or vulnerable to population decline. Some of the major factors influencing the status of mussels are poor water quality, increasing sediment due to increased erosion and the restriction of fish migrations due to the construction of dams (fish act as hosts for mussel larvae). Prof. Hornbach and his students have worked with the National Park Service, Minnesota Department of Natural Resources, and other agencies to provide information that will assist them in development management plans for mussels in MN. Their work has been presented at a number of regional and national meetings and has resulted in co-authored publications in the peer-reviewed literature.