Ecological effects of an invasive mud snail and its body-snatching parasites: Implications for organic matter cycling in a eutrophic estuary

In this dissertation, I address the implications of a poly-species invasion consisting of a mud snail (Batillaria attramentaria) and the novel trematode parasite that uses the snail as a host, and I characterize the effects of this invasion on organic matter cycling in Elkhorn Slough. In Chapter 1, I used field transect surveys and a mark-recapture experiment to show that trematodes induced snails to increase growth and alter their habitat use. In Chapter 2, I used a field enclosure experiment to investigate the effects of parasitic modifications to Batillaria on the snail’s food resources and on sediment chemistry, showing that parasitic effects on snails have profound effects on benthic community structure and function. In Chapter 3, I investigated Batillaria’s interactions with a bloom-forming macroalga. I used a laboratory experiment to show that the snail could facilitate the algae by increasing its growth in nutrient-replete water, and allowing it to persist in low-nutrient water, potentially exacerbating blooms that cause hypoxia and other ecological problems. My dissertation underscores the context-dependency of ecological interactions, and highlights interactions that should be more widely recognized in forward-thinking ecosystem management