2025-11-03 マックス・プランク研究所
A CTD rosette on board RV Poseidon. With this device, scientists can measure environmental parameters and collect water samples from deep ocean layers.© MPI f. Marine Microbiology/ Jana Milucka
＜関連情報＞
- https://www.mpg.de/25651138/nitrous-oxide-is-trapped-in-the-black-sea
- https://aslopubs.onlinelibrary.wiley.com/doi/10.1002/lno.70182
黒海の亜酸素層における亜酸化窒素の循環 Nitrous oxide turnover in the suboxic zone of the Black Sea
Jan N. von Arx, Katharina Kitzinger, Hannah K. Marchant, Gaute Lavik, Joerdis Stuehrenberg, Jon S. Graf, Daan R. Speth, Marcel M. M. Kuypers, Jana Milucka
Limnology and Oceanography Published: 15 August 2025
DOI:https://doi.org/10.1002/lno.70182
Abstract
The Black Sea is the largest meromictic marine basin characterized by well-oxygenated surface waters and a deep sulfidic anoxic core, separated by a ca. 50-m-thick suboxic zone. Nitrogen cycling at oxic-anoxic boundaries of oxygen-depleted marine environments has been identified as a major source of nitrous oxide (N2O), a potent greenhouse gas. Contrary to this, previous work suggests that the Black Sea is considered only a minor N2O emitter. We measured persistent potential N2O formation from ammonia oxidation (up to 0.2 nmol N L−1 d−1) and sporadic rates of high N2O production from denitrification (up to 20 nmol N L−1 d−1) in the suboxic zone of the western Black Sea. Molecular analysis identified the Nitrososphaerales as the dominant ammonia oxidizers, while the genetic potential to form N2O from nitrite via denitrification was mainly encoded by Alpha- and Gammaproteobacteria. The measured potential N2O reduction rates (up to 24 nmol N L−1 d−1) could exceed N2O formation rates from both nitrite and ammonia, with the capacity for N2O reduction mainly encoded and expressed by presumably chemolithotrophic Gammaproteobacteria and Marinisomatia. Our results suggest that, despite the diverse pathways of N2O production operating in the Black Sea, the low emissions likely result from tight coupling of N2O production and consumption, facilitated by the presence and activity of organisms that seem to be specialized in N2O reduction.
