Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

M.S. in Biological Science

First Advisor

Colin Jackson

Second Advisor

Peter Zee

Third Advisor

Ryan Garrick

Relational Format



Freshwater mussels are important for nutrient cycling and ecosystem health, as they filter feed on their surrounding water column. This form of feeding makes these bivalves especially sensitive to conditions in their environment. Gut microbial communities (microbiomes) have been recognized as important to both host organism and ecosystem health; however, how microbiomes are organized and influenced is still unclear. In this study, the gut microbiomes of 58 individuals of the freshwater mussel Amblema plicata were compared across two river basins, five rivers, and nine sites in the southeastern USA. Planctomycetes, Firmicutes, and Cyanobacteria were the most common phyla within all mussels. However, the relative abundances of these major bacterial phyla were different in gut microbiomes of A. plicata taken from different rivers and river basins. The relative abundance of major bacterial operational taxonomic units (OTUs) also differed in mussels collected from different sites, rivers, and river basins Despite these differences, a core microbiome was identified across all mussels, with eight OTUs being consistent members of the A. plicata microbiome at all sites, the most abundant OTU identifying as a member of Planctomycetaceae. Distance between sites was not correlated to similarity in the gut microbiome, which was more related to site physicochemistry. These results suggest that while physicochemical conditions affect the composition of transient bacteria in the mussel gut microbiome, the core microbiome is largely unaffected, and a portion of the A. plicata microbiome is retained regardless of the river system.

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