Thermal Rearrangement of Dissolved Organic Matter-Microbe Interactions Magnifies the Climate Forcing Potential of Northern Lakes

Dissolved organic matter (DOM) represents one of Earth’s largest and most reactive carbon pools, with its molecular composition influencing its environmental persistence and ecosystem function. Anthropogenic warming, which is most pronounced in northern ecosystems, is rapidly altering the dynamics of DOM production, export, and processing in aquatic systems. Here, we present a large scale (1600 km) space-for-time substitution across a boreal-to-temperate gradient to test the hypothesis that warming fundamentally reworks the relationships between DOM composition, microbial community function, and carbon emissions. We sampled 40 lakes over all seasons, integrating molecular-level DOM characterization, shotgun metagenomics sequencing of microbial communities, in situ measurements of GHG fluxes, and assessments of lake metabolism. We found that warming moves lakes along a continuum from CO₂-dominated systems to potent CH4 emitters, driven by a thermal reorganization of both DOM composition and microbial community structure. By linking high-resolution chemodiversity data with microbial taxonomy and ecosystem function, this research provides a mechanistic framework to predict how climate-driven shifts in ecosystem function and structure will alter the role of northern lakes in the global carbon cycle. These findings are critical for informing models of future atmospheric carbon loading and guiding climate mitigation and freshwater resource protection policy.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Sommer Starr, Trent University (sommerfaithstarr@gmail.com)

Authors:

Sommer Starr, Trent University  (sommerfaithstarr@gmail.com)

Michael Eckert, Trent University  (mikeeckert@trentu.ca)

Vincent Lau, Trent University  (vincentlau@trentu.ca)

Celeste Milli, Trent University  (celestemilli@trentu.ca)

Marissa Ingratta, Trent University  (marissaingratta@trentu.ca)

Teya Helae, Trent University  (teyahelae@trentu.ca)

Andrew Tanentzap, Trent University  (atanentzap@trentu.ca)