Fig 1. N–cycle emphasising the production of N₂O through denitrification (grey arrows) and nitrification (red arrows).

The production of N₂ through anammox is presented with green arrows. Arrow width indicates suggested pathway importance in the south-eastern Indian Ocean. Marker genes for the different steps of the nitrogen cycle are in italics. The nitrous oxide reductase gene (nosZ) is highlighted with a dashed blue circle. Heterotrophic denitrification (nir/nor genes) is highlighted as a C source while the autotrophic anammox process (hzsA genes) is highlighted as a C sink. Note: dissimilatory reduction of NO₂⁻ to NH₄⁺ and N₂O is not presented on this figure. Figure adapted from Throbäck et al. [53]