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Tuesday, January 26 • 11:20am - 11:40am
Longitudinal Patterns of Freshwater Mussel Assemblage Structure in Rivers of Central Michigan, U.S.A

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AUTHORS: Amanda J. Chambers, Daelyn A. Woolnough – Department of Biology, Central Michigan University

ABSTRACT: A primary focus in the study of lotic ecosystems involves understanding the relationship between changes in the physical environment and corresponding changes in biota along a longitudinal gradient. Previous studies examining patterns in the downstream succession of riverine organisms, primarily fish, have noted two commonly occurring patterns: either the restriction of species to discrete zones (i.e., biotic zonation or species turnover) or the gradual addition of species with increasing distance from the headwaters (i.e., continual addition or nestedness). These patterns can be influenced by both natural variation in the landscape and by anthropogenic disturbances. Like other riverine organisms, freshwater mussels (Family: Unionidae) exhibit longitudinal patterns in distribution and abundance; however, the patterns and processes by which downstream succession occurs, and the environmental variables that structure mussel assemblages are poorly understood. This study examined patterns in the longitudinal distribution and abundance of freshwater mussel assemblages in the Pine and Chippewa rivers, Michigan. A stratified random design based on differences in surficial geology was used to sample mussels at 54 sites (28 in the Chippewa River, 26 in the Pine River). Timed-searches were used to semi-quantitatively assess differences in relative abundance and diversity among sites and between rivers. Preliminary results suggest that differences in mussel assemblage structure are consistent with upstream to downstream changes in surficial geology in both rivers. Certain species were found to be restricted to specific geologies suggesting that downstream succession of mussels may proceed primarily via biotic zonation. Given that both rivers exhibited similar patterns in terms of longitudinal assemblage structure, we expect that these patterns are likely to prevail in similar glaciated regions of the upper Midwest.

Tuesday January 26, 2016 11:20am - 11:40am EST
Vandenberg B