A comprehensive synthesis of mussel-driven ecosystem processes and their role in freshwater sustainability. Freshwater mussels are among the most endangered animals on the planet--and some of the most ecologically important. As powerful filter feeders and ecosystem engineers, mussels influence everything from water clarity and nutrient cycling to the structure of entire aquatic communities. In The Functional Ecology of Freshwater Mussels, Caryn C. Vaughn offers the most comprehensive synthesis to date of how mussels shape the ecosystems they inhabit. Integrating more than 30 years of original field and laboratory research with a rapidly expanding global literature, Vaughn examines how mussels support water quality, contribute to biogeochemical processes, influence food web dynamics, and enhance biodiversity across aquatic and adjacent terrestrial environments. Chapters detail the biology and life history of mussels, the complex interactions within their communities, and the environmental conditions that influence their performance. Vaughn shows how species-specific traits and environmental context shape the magnitude of diverse mussel functions. With attention to the consequences of species composition, habitat variation, and climate stressors, the book shows how mussel-driven processes scale from individual organisms to entire river systems. Vaughn presents practical strategies for conservation and explains how effective restoration requires linking mussel biology with the goals of broader ecosystem management. The Functional Ecology of Freshwater Mussels is an essential reference for ecologists, conservation professionals, aquatic resource managers, and policymakers concerned with the sustainability of freshwater systems.