ABSTRACT

The Laurentian Great Lakes hold 20% of our planet's surface freshwater and 84% of US surface freshwater, comprising the largest freshwater ecosystem on Earth. They provide critical ecosystem services such as fisheries and recreation, and serve as the drinking water source to 40 million people. In recent decades, the Great Lakes have experienced significant environmental changes, such as nutrient pollution and invasive species, that have altered water chemistry and food web structure. In particular, the base of the food web has changed dramatically. Annual spring phytoplankton blooms have largely disappeared in Lakes Michigan and Huron, while toxic cyanobacterial blooms have increased in Lake Erie. The microorganisms that make up the base of the food web in the Great Lakes are poorly understood and play critical roles in regulating water quality and ecosystem productivity. This project characterizes single-celled cyanobacteria across the Laurentian Great Lakes to understand their genetic diversity and ecology. The investigators are working with local high schools on Chicago's south side to develop teaching modules about the role of microorganisms in the health of the Great Lakes. Local high school teachers will be engaged to design lessons about aquatic microbial ecology, with the goal of increasing Great Lakes literacy and STEM participation in Chicago's impoverished and diverse south side communities.

Picocyanobacteria contribute up to 50% of primary production in some portions of the Laurentian Great Lakes. However, little is known about their population structure and dynamics, or about factors shaping their abundance and activity. Understanding controls on picocyanobacterial diversity and function is crucial for developing predictive biogeochemical models for the Great Lakes in the face of rapid environmental change. Multiple phylogenetic groups of coexisting picocyanobacteria in the Great Lakes have recently been identified, and this project characterizes their genetic, physiological, and ecological diversity. Using a combination of flow cytometry and molecular sequencing approaches, distinct populations are being quantified across lakes, depths, and seasons, and comparative genomics is being used to reveal how pathways and genes are distributed across taxa and habitats. Quantitative transcriptomics and proteomics are being used to diagnose environmental controls on gene expression and to assess the relative activity of distinct populations. Ongoing time series data and archived samples are being combined with targeted sampling aboard the R/V Blue Heron. This project advances our knowledge of the Great Lakes microbial food web by generating the first systematic picture of picocyanobacterial diversity in this ecosystem.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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