Seasonal temperature rise influences nitrous oxide and methane accumulation in freshwater habitats via distinctive...

Under global warming, the microbial mechanism linking seasonal temperature rise to nitrous oxide (N₂O) and methane (CH₄) dynamics in freshwater habitats remains unclear. This study sampled water/sediment from 4 habitats in fragmented rivers (Liangtan River, Chongqing, China) in winter and summer, analyzing environmental parameters, N₂O/CH₄, and microbial communities. Results showed that seasonal temperature rise (winter: 8.3-12.1 °C; summer: 27.7-36.1 °C) was associated with increased CH₄ concentrations (0.049-2.40 vs 0.054-34.06 μmol/L) and decreased N₂O concentrations (0.022-0.112 vs 0.009-0.059 μmol/L) in water. Mechanistically, seasonal temperature rise was linked to the increased total particulate matter (a key substrate for methanogens) and the reduced abundance of Methylocystis (a dominant methane oxidizer), which may contribute to CH₄ accumulation. For N₂O, seasonal warming was associated with increased the relative abundance of Steroidobacteraceae and Dechloromonas (bacteria that are capable of complete denitrification). These findings improve the understanding of the mechanisms through which seasonal temperature rise influences greenhouse gas dynamics in freshwater habitats, and provides valuable insights for fragmented river management and greenhouse gas mitigation.