Award: OCE-1737368

Invasive species are a key threat to the health of earth’s ecosystems. The main goal of our research was to measure the effects of one of the world’s most aggressive freshwater invasive species, the quagga mussel, on carbon (C), nitrogen (N), and phosphorus (P) cycling in the Laurentian Great Lakes (LGL). The five LGL are the largest freshwater ecosystem on the planet, and provide drinking water, recreation, and fish to millions of people in the US and Canada. The amount and movement of C, N, and P in lakes have large effects on their productivity and water quality. Because of this, it is important to understand how quagga mussels affect the dynamics of these elements in the LGL and other lakes. To address our research questions, we combined field sampling, experiments, and modeling. We surveyed the distribution of quagga mussels in Lakes Michigan and Huron, and collected samples of mussels to measure the rates at which mussels store and recycle C, N, and P. We also collected sediment samples to measure the exchange of C, N, and P between the water column on the lake bottom at places with different numbers of mussels and types of sediment. We took quagga mussels and native sediment-dwelling animals to the lab to make long term studies of how environmental conditions affect the biology of these organisms and how they interact with water and sediments. The results of our experiments and field observations helped build computer models of how the quagga mussel invasion changed the balance of C, N, and P in the Great Lakes. Our results show that quagga mussel populations are expanding and moving to deeper water in Lake Michigan. This means their impacts on the lake are likely to keep getting stronger. Lab experiments showed that quagga mussels are extremely tolerant of starvation, and their effects on the movement and storage of C, N, and P change depending on the environmental conditions they are exposed to. We also found that quagga mussels interact with sediments in different ways than native sediment animals, which can affect how much C, N, and P is stored in the sediments and how much is released into the water column. Our models show that, because of their enormous population, quagga mussels are the main controller on phosphorus cycling in the LGL. This means that changes in their abundance will have large impacts on water quality and productivity. All together, this research is helping to understand the biogeochemistry of nutrient cycling, how invasions affect aquatic ecosystems, and how the LGL, and other lakes, will respond to future environmental change. Broader impacts of this work focused on training and education and science outreach to the public. This project supported training of six undergraduate and three graduate students and one postdoctoral researcher. During our research cruises aboard the research vessel Blue Heron we visited the Milwaukee Discovery World Science and Technology Museum and Chicago’s Navy Pier. There, hundreds of visitors came aboard the Blue Heron to tour the vessel and learn about the ecology of the Great Lakes. Members of our research team also participated in two documentary films. One was produced by Minnesota’s Bell Museum (Stories Aboard the Blue Heron) and another is currently in production and slated to be released in 2024 (All Too Clear). Last Modified: 02/27/2023 Submitted by: Tedy Ozersky