WHY ARE MUSSELS LARGER IN THE SUNRISE RIVER THAN IN THE ST. CROIX RIVER?

Elise Griffin, Macalester College
Daniel J Hornbach, Macalester College
Mark C. Hove, Macalester College
Kelly R. MacGregor, Macalester College

Evidence suggests that some small low-head dams benefit and increase growth rates for downstream filter-feeding guilds (Singer, 2010). The purpose of this study was to study why mussels of the species, Actinonaias ligamentina are larger in the Sunrise River below a small low-head dam than above and below the larger hydroelectric dam on the Saint Croix River at St. Croix Falls, WI. We addressed this question by collecting water samples to determine total suspended solids of organic matter, inorganic matter, and chlorophyll levels (indicators of food quantity and quality) above and below the Kost Dam on the Sunrise River and the St. Croix Falls Dam on the St. Croix River. We found that mussels in the Sunrise River below the Kost Dam are growing at a faster rate than mussels on the St. Croix; however, there is no statistically significant difference in food available or quality between locations. We continue to seek temperature data for the Sunrise River to examine whether temperature differences are important. It is essential to understand how dams may benefit, degrade and alter river mechanisms and habitat characteristics that determine the well being of mussel communities in Minnesota and globally so that we can better make intelligent and informed decisions about dam construction and removal where mussels and other aquatic species reside.

Suggestions for Reading

Singer, E. E. 2010. Mill dam effects on freshwater mussel growth in a small Alabama (USA) stream. Master’s Thesis, Appalachian State University,40 p.

Feminella, J., M. Gangloff, E.Hartfield, Brian Helms, David Werneke, Kevin White, and Jack W. Feminella. 2009. Alabama Mill Dam Inventory Final Report. Appalachian State University, Auburn University, Appalachian State Univeristy, 24 p.