Role Of Invasive Dreissenid Mussels In The Biogeochemical Cycling Of Carbon, Nitrogen And Phosphorus In Minnesota Lakes

Abstract

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 research 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. In the context of ecological stoichiometry and homeostasis theory we examined mussel C:N:P tissue and shell content, excretion and biodeposition rates finding that mussels of different sizes and in different lakes store and remineralize different amounts of nutrients. This information is presented in Chapter 1 of the thesis. We also measured dreissenid living biomass and discarded shell mass and used the results from chapter 1 (tissue and shell nutrient composition (C, N, and P), and excretion and biodeposition rates) to construct nutrient budgets for dreissenids in different types of lakes. Variation in the total and relative biomass of soft tissues, live shell and discarded shell material resulted in different contribution of dreissenid populations to nutrient and carbon cycling. 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.