Impacts of Terrestrial Organic Matter on Methanogenic Archaea in Littoral and Pelagic Sediments of the Mississippi River Headwaters from June to September 2020 (Cyanos Great Lakes Project)

Terrestrial organic matter (tOM) plays a key role in aquatic ecosystems, influencing carbon cycling and greenhouse gas emissions. Here, we investigate how tOM affects methane production in littoral and pelagic sediments from the Mississippi River headwaters using a controlled microcosm approach. Contrary to expectations, tOM additions consistently enhanced methane production across both sediment types, with no significant differences between littoral and pelagic zones. Methane generation was mediated by specific sediment microorganisms—primarily methanogens and lignocellulose-degrading bacteria—which exhibited similar responses across habitats.

Sequencing data associated with this paper is available on NCBI through the project PRJNA1164797: Impacts of Terrestrial Organic Matter on Methanogenic Archaea in Littoral and Pelagic Sediments of the Mississippi River Headwater.

Our results highlight the contribution of cytochrome-containing methanogens and their syntrophic interactions with fermentative bacteria, underscoring the importance of microbial community composition in regulating sediment methane dynamics. These findings suggest that increasing tOM loads to freshwater systems could have broader implications for methane emissions, driven by specific microbial interactions.