Direct biological fixation provides a freshwater sink for N2O

• Published in: Nature communications 2023-10, Vol.14 (1), p.6775-6775, Article 6775
• Main Authors: Si, Yueyue, Zhu, Yizhu, Sanders, Ian, Kinkel, Dorothee B., Purdy, Kevin J., Trimmer, Mark
• Format: Article
• Language: English
• Subjects: 38/22; 38/23; 38/77; 704/172; 704/47/4112; Denitrification; Humanities and Social Sciences; multidisciplinary; Natural waters; Nitrates; Nitrogen fixation; Nitrogenase; Nitrogenation; Nitrous oxide; Ozone depletion; Ponds; Science; Science (multidisciplinary); Temperature
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-42481-2

Nitrous oxide (N 2 O) is a potent climate gas, with its strong warming potential and ozone-depleting properties both focusing research on N 2 O sources. Although a sink for N 2 O through biological fixation has been observed in the Pacific, the regulation of N 2 O-fixation compared to canonical N 2 -fixation is unknown. Here we show that both N 2 O and N 2 can be fixed by freshwater communities but with distinct seasonalities and temperature dependencies. N 2 O fixation appears less sensitive to temperature than N 2 fixation, driving a strong sink for N 2 O in colder months. Moreover, by quantifying both N 2 O and N 2 fixation we show that, rather than N 2 O being first reduced to N 2 through denitrification, N 2 O fixation is direct and could explain the widely reported N 2 O sinks in natural waters. Analysis of the nitrogenase ( nifH ) community suggests that while only a subset is potentially capable of fixing N 2 O they maintain a strong, freshwater sink for N 2 O that could be eroded by warming. Denitrification is still widely considered as the only natural sink for N 2 O here we show how direct biological fixation represents an alternative sink for this potent climate gas.