Investigating Freshwater Mussel Disease and Mortality in the Clinch River Within a Population Ecology Framework

Freshwater mussels (order Unionida) play an important role in aquatic ecosystems, providing essential ecosystem services to humans and wildlife. The United States harbors the highest diversity of mussels globally, yet nearly 70% of known species are considered imperiled. The Clinch River, a major biodiversity hotspot for mussels in the Unites States, has experienced recent mass mortality events (MMEs) dramatically affecting multiple species. Studying MMEs is inherently challenging due to their unpredictability and the frequent scarcity of reference data on mortality dynamics of affected populations. In this dissertation, we fill knowledge gaps by elucidating patterns, processes, and factors influencing mortality within mussel populations in the Clinch River. We use a combination of pathological, toxicological, microbiological, and ecological assessments to identify potential causal agents, detect environmental risk factors, and characterize demographic structure of affected individuals. We also apply epidemiological concepts to analyze archived shells and gain etiological insights into past MMEs. This research provides critical insights into the disease and mortality dynamics influencing mussel populations. Lastly, we discuss lessons learned from historical mortality events and propose strategies to enhance response to future MMEs.