RESOURCE PARTITIONING AMONG FRESHWATER MUSSELS

Cara Weggler, Department of Environmental Studies, Macalester College, St. Paul MN
Daniel J. Hornbach, Departments of Environmental Studies and Biology, Macalester College, St. Paul MN
Kelly R. MacGregor, Department of Geology, Macalester College, St. Paul MN
Mark C. Hove, Department of Biology, Macalester College, St. Paul MN

Studies have shown Bivalves, particularly mussels are an important part of freshwater ecosystems (Strayer et al. 2004, Vaughn, Nichols, & Spooner 2008). As benthic filter feeders, mussels help to complete the nutrient cycle within rivers by transferring the nutrients and energy in the water to the sediment. However due to their sedentary nature, mussels are particularly vulnerable to human activity like the impoundment of rivers and agricultural and urban runoff. Even though North America has the most freshwater mussel species in the world, 43% of the taxa are now extinct, endangered, or threatened (Hornbach et al. 1996). Therefore in order to help conserve freshwater mussels species and also freshwater ecosystems it is important to investigate mussels and their interaction within the aquatic community (Vaughn, Nichols, & Spooner 2008). This study investigates whether mussels differ in habitat by examining sediment size, an indicator of sedimentation and quality of mussel habitat (Box & Mossa 1999). Six freshwater mussel species were analyzed: Actinonaias ligamentina (Mucket), Amblema plicata (Threeridge), Elliptio dilatata (Spike), Fusconaia flava (Wabash pigtoe), Quadrula pustulosa (Wartyback), and Truncilla truncata (Deertoe). Mussels and their surrounding sediment were quantitatively sampled at twelve sites along the St. Croix and Mississippi rivers. Sediment size was analyzed with the phi scale. Using ANOVA, three species (A. ligamentina, A. plicata, and E. dilatata) were found to significantly differ by age in habitat preferences within species (p= .05, p= .03, p= .02). Using the Tukey's HSD test, significant differences in habitat were found among all juveniles (p < .0001) and adults (p < .00001). Although for two species, E. dilatata and A. ligamentina, there was no significant difference. Overall, results indicate mussels at least partially apportion habitat spaces by sediment size.

References:

Box, J.B. & Mossa, J. (1999). "Sediment, land use, and freshwater mussels: prospects and problems." Journal of the North American Benthological Society. 18(1): 99-117.

Hornbach, D., et al. (1996). "Factors Influencing the Distribution and Abundance of the Endangered Winged Mapleleaf Mussel Quadrula fragosa in the St. Croix River, Minnesota and Wisconsin." American Midland Naturalist. 136(2): 278-286.

Strayer, D.L., et al. (2004). "Changing Perspectives on Pearly Mussels, North America's Most Imperiled Animals." Bioscience. 54(5): 429-439.

Vaughn, C.C., Nichols, S. J. & Spooner, D. E. (2008). "Community and Foodweb Ecology of Freshwater Mussels." Journal of the North American Benthological Society. 27(2): 409-423.