MS Thesis Defense


Felicia Williamson
Masters Student, Water Resources Science

August 17, 2017


Thesis Title
Role of Invasive Mussels (Dreissena polymorpha) in the Biogeochemical Cycling of Carbon, Nitrogen, and Phosphorus in Minnesota Lakes

Dreissenid (zebra and quagga) mussels were introduced to North America in the 1980s, and have colonized numerous freshwater systems since then, causing major ecological changes, including restructuring of nutrient dynamics. Although work has been done on dreissenid effects on elemental cycling, most studies are limited to a single system or single aspect of dreissenid effects, making it difficult to make general statements about dreissenid effects on nutrients in invaded systems. The goal of this research was to quantify and provide an integrated view of the role of invasive dreissenid mussels in biogeochemical dynamics through the development of nutrient budgets for dreissenid populations in 8 Minnesota lakes spanning large gradients of size and trophic status. We measured dreissenid living biomass, discarded shell mass, tissue and shell nutrient composition (C, N, and P), and excretion and biodeposition rates of C, N and P. Nutrient budgets were constructed for dreissenids in different types of lakes in the context of ecological stoichiometry and homeostasis theory. The results provide new insights and a more holistic understanding of the role of dreissenid invaders in varying lake systems, which allows better prediction of dreissenid impacts on biogeochemistry of different lakes.