Issue Date: August 1, 2011
Archaea May Be Key Nitrous Oxide Source
The large quantities of the ozone-destroying greenhouse gas nitrous oxide (N2O) released from Earth’s oceans into the atmosphere may be generated by single-celled archaea, rather than bacteria, scientists report (Science, DOI: 10.1126/science.1208239). Although oceanic bacteria had been thought to produce most of Earth’s marine N2O via oxidation of ammonia and reduction of nitrogen oxides, that idea never jibed with isotopic N2O studies that compared the microbially produced gas with N2O in the atmosphere. Karen L. Casciotti and Alyson E. Santoro of Woods Hole Oceanographic Institution and their colleagues now show that cultures of marine archaea produce N2O via ammonia oxidation. In addition, they found that the isotope ratios of oxygen and nitrogen in the archaea-produced N2O and in atmospheric N2O contributed by the ocean are similar. The results “suggest that ammonia-oxidizing archaea likely play an important role in N2O production in the near-surface ocean,” the researchers write.
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