Response of N(2)O production rate to ocean acidification in the western North Pacific

Ocean acidification induced by the increase of anthropogenic CO(2) emissions has a profound impact on marine organisms and biogeochemical processes.(1) The response of marine microbial activities to ocean acidification might play a crucial role in the future evolution of air-sea fluxes of biogenic gases such as nitrous oxide (N(2)O), a strong greenhouse gas and the dominant stratospheric ozone-depleting substance.(2) Here, we examine the response of N(2)O production from nitrification to acidification in a series of incubation experiments conducted in subtropical and subarctic western North Pacific. The experiments show that, when pH was reduced, the N(2)O production rate during nitrification measured at subarctic stations increased significantly whereas nitrification rates remained stable or decreased. Contrary to what was previously thought, these results suggest that the effect of ocean acidification on N(2)O production during nitrification and nitrification rates are likely uncoupled. Collectively these results suggest that, if seawater pH continues to decline at the same rate, ocean acidification could increase the marine N(2)O production during nitrification in subarctic North Pacific by 185 to 491% by the end of the century.