2025 Midwest Fish & Wildlife Conference

AUTHORS:  Madison Dunlap, Central Michigan University Biology Department and Institute for Great Lakes Research; Daelyn Woolnough, Central Michigan University Biology Department and Institute for Great Lakes Research

ABSTRACT:  Unionids (i.e., native freshwater mussels) provide essential ecosystem services to other benthic macroinvertebrates by concentrating nutrients as well as stabilizing substrate. Research has indicated that different unionid species may contribute unequally to ecosystem services which may be particularly important to epizoic macroinvertebrates living on live unionids. This research sought to understand what ecosystem factors or unionid traits contribute to structuring the epizoic assemblage and how epizoic assemblages relate to the larger benthic macroinvertebrate assemblage. Metadata was collected from unionid surveys between 2015-2023 from across the Chippewa River, Michigan USA. Macroinvertebrate and epizoite data, as well as additional data to fill in data gaps from metadata analyses, were collected during the summer of 2024 at 12 Chippewa River sites. Questions we ask include: 1) What macroinvertebrate assemblages are using live unionids as habitat, 2) Do different traits of unionid shells (e.g., smooth, bumpy, size) contribute to different epizoic assemblages and, 3) How does the epizoic assemblage on unionids compare to traditional D-net macroinvertebrate assemblages? This study considered 5 species of unionids. Analyses is ongoing but will include a comparison of epizoite and benthic macroinvertebrate data across biotic and environmental factors, a prediction of the epizoite density and species richness of epizoite macroinvertebrates based on unionid host traits, and a comparison of epizoic assemblage metrics. Overall, we predict that macroinvertebrate epizoic assemblage will differ from the surrounding benthic macroinvertebrate assemblage and will be structured based on unionid traits. Results give insight into how changes in unionid assemblages, like species extinction and declines, may impact ecosystem services and how data on benthic macroinvertebrates can inform this research. This work is the first to quantify epizoic organisms across multiple species of unionid hosts and compare epizoic macroinvertebrate assemblage to the surrounding macroinvertebrate assemblage.