Wildfire-Derived Pyrogenic Dissolved Organic Matter (pyDOM) Enhances Riverine DOM Reactivities and Nitrogen...

Area of Science:

• Environmental Chemistry
• Microbial Ecology
• Biogeochemistry

Background:

• Wildfires significantly alter soil organic matter, impacting global carbon cycling.
• The effects of pyrogenic dissolved organic matter (pyDOM) on riverine dissolved organic matter (DOM) reactivity and microbial metabolism are not well understood.

Purpose of the Study:

• To investigate the molecular transformations of DOM and microbial responses in river water amended with pyDOM.
• To assess the impact of pyDOM on DOM reactivity, microbial diversity, and metabolic pathways.

Main Methods:

• Controlled incubation of river water with DOM from wildfire-affected and undisturbed soils.
• High-resolution mass spectrometry and substrate-explicit modeling for DOM analysis.
• Reactomics analysis and PICRUSt2 for microbial response and genomic insights.

Main Results:

• PyDOM introduction increased refractory DOM components with high aromaticity and double bond equivalents.
• PyDOM enhanced DOM reactivity and altered microbial communities, increasing filamentous cyanobacteria and boosting nitrogen metabolism.
• Genomic analysis revealed pyDOM-driven enrichment of denitrification pathways, particularly aerobic denitrification.

Conclusions:

• PyDOM acts as a biogeochemical vector, transferring terrestrial carbon into aquatic ecosystems.
• Findings highlight the need to incorporate pyDOM fluxes into climate-relevant biogeochemical frameworks.
• PyDOM influences riverine microbial metabolism and nitrogen cycling, with implications for carbon sequestration.