Water and sediment act as reservoirs for microbial taxa associated with invasive dreissenid mussels

Zebra mussels (Dreissena polymorpha) are invasive, filter-feeding, bivalves that have disrupted the ecology of thousands of freshwater biomes across North America. Due to their efficient filter-feeding activity, zebra mussels (ZMs) and other bivalves are extensively used to detect chemical contamination in waterways. In this study, we evaluated whether water and sediment serve as major sources of ZM tissue-associated microbiota, and whether ZMs serve as a reservoir for potentially pathogenic microbes in aquatic systems. High-throughput DNA sequencing of 16S rRNA gene was done to characterize the microbial community structure in 472 environmental samples, comprising ZMs, sediment, and the water column, collected from 15 lakes during the summer and fall months. Sequence analyses, done using the SourceTracker program, predicted that water and sediment contributed up to 91 and 86%, respectively, to the structure of microbiota within ZMs, and that mussels from the same site showed nearly identical source microbiota profiles. The relatively high local source contribution suggests that the microbiota in ZM tissue has the potential to reflect biological contamination and this phenomenon can be used to monitor microbial water quality. A preferential enrichment of several taxa was also observed in ZM tissues, including potential pathogenic groups such as Aeromonas, Enterobacteriaceae, and Pseudomonas. Taken together, our results contribute to an improved understanding of ZMs as a sentinel species in aquatic habitats and its potential impact to water quality management.