Keywords
Abstract
Permafrost regions store 1400-1600 Pg of soil organic carbon, increasingly vulnerable to climate change. This study investigated microbial succession during permafrost thaw in Siberia using integrated metagenomic-metabolomic approaches. Samples spanned a thaw gradient: intact permafrost (-2.1°C), transitional zones (1.8°C), and thawed thermokarst (6.4°C). Metagenomic analysis showed 4.5-fold increase in methanogenesis genes versus 1.8-fold for methane oxidation. Methane emissions increased 240-fold (0.02±0.01 to 4.8±0.7 mg m⁻² h⁻¹), CO₂ fluxes rose from 12.3±2.1 to 89.6±12.4 mg m⁻² h⁻¹. Temperature sensitivity (Q10) for methane production increased from 2.8 to 4.2. Metabolomics identified methylamine/trimethylamine accumulation in transitional zones, indicating methanogenic bottlenecks. Enhanced syntrophic partnerships between fermentative bacteria and methanogens emerged in thawed environments. Microbial metabolic restructuring amplifies greenhouse gas emissions beyond temperature effects, suggesting climate models underestimate permafrost carbon-climate feedbacks.