Metagenomic and metatranscriptomic insights into the metabolic capabilities of sediment microbial communities in oligotrophic Lake Superior

Sediment microbes drive many core ecosystem functions and influence the fate of contaminants in freshwater ecosystems. Despite their importance, the interactions within these diverse assemblages remain underexplored, especially in oligotrophic lakes such as the Laurentian Great Lake Superior. As part of the Great Lakes Sediment Surveillance Program, we examined the abundance, diversity, and metabolic pathways of microbial communities in surface sediments of oligotrophic Lake Superior. Using metagenomic and metatranscriptomic approaches, we identified patterns and mechanisms of carbon, nitrogen, and sulfur cycling across the lake’s sediments. Our results show that Lake Superior sediments harbor aerobic, catalase- and oxidase-positive genera including nitrifiers, ammonia oxidizers, sulfur oxidizers, and methanotrophs. These findings align with the predominance of aerobic chemoheterotrophic, methylotrophic, and methanotrophic metabolisms that would be expected considering the sediment’s electron-accepting conditions. While abundances for different metabolic pathways did not significantly differ across offshore sediments, photosynthetic and oxidative phosphorylation genes were expressed in sediments collected near river mouths, which also exhibited unique community structures compared to offshore sediments. This study improves our understanding of metabolic capabilities of sediment microbial communities in low-nutrient lakes, serving as baseline information for assessing how microbially driven biogeochemical processes respond to anthropogenic stressors in Lake Superior and potentially across the Laurentian Great Lakes.

Presentation Preference: Oral

Primary Presenter: Chan Lan Chun, University of Minnesota Duluth (chun0157@d.umn.edu)

Authors:

Andrew Wood, University of Minnesota Duluth / Natural Resources Research Institute  (wood0795@d.umn.edu)

Britta Larson, University of Minnesota Duluth / Natural Resources Research Institute  (lars5859@d.umn.edu)

Christopher Filstrup, University of Minnesota Duluth / Natural Resources Research Institute  (filstrup@d.umn.edu)

Molly Mikan, University of Minnesota Duluth / Natural Resources Research Institute  (mpmikan@gmail.com)