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Abstract 

Whirling disease is on the rise since its introduction in the United States in 1958 and is a health problem both in fisheries and in wild populations of salmonids. Prevalence of the disease is dependent on ecological context and interactions among multiple other species, including algal species such as the also invasive diatom Didymosphenia geminata, the oligochaete worm Tubifex tubifex, and the myxozoan parasite Myxobolus cerebralis that is the causative agent of whirling disease in salmonid fishes. D. geminata, a stalk-producing diatom has increased in frequency worldwide and is now invasive across the United States. The stalks of D. geminata create an environment suitable for oligochaetes such as T. tubifex. Based on existing data oligochaete abundance is higher in areas with higher percent cover of D. geminata, and whirling disease prevalence in trout is 3X higher in streams with blooms. My research further examined why oligochaetes are more abundant specifically in streams with D. geminata blooms focusing on the mechanisms that might promote T. tubifex density increases, including predator release. The results provide some new insights into the multifaceted and complex ecological interactions that can promote increased amounts of whirling disease in ecologically and economically important salmonid fishes. I attempt to place these results in the context of a larger collection of ecological drivers that explain interactions among all the actors involved.