Anaerobic nitrification-denitrification mediated by Mn-oxides in meso-tidal sediments: Implications for N-2 and N2O production

作者：Fernandes Sheryl Oliveira; Javanaud Cedric; Aigle Axel; Michotey Valerie D; Guasco Sophie; Deborde Jonathan; Deflandre Bruno; Anschutz Pierre; Bonin Patricia C^*

来源：Journal of Marine Systems, 2015, 144: 1-8.

DOI：10.1016/j.jmarsys.2014.11.011

• Anaerobic
• Anammox
• Denitrification
• Manganese oxides
• Nitrification
• Nitrous oxide
• Sediments

Field measurements in the Arcachon Bay (southwest France) indicated anaerobic production of NOx via nitrification, which was coupled to the reduction of Mn-oxides. To prove the occurrence of this process, laboratory microcosm experiments were set up. A N-15 tracer-based approach was used to track if NOx produced through Mn-oxide-mediated anaerobic nitrification would be reduced to N-2 via denitrification or anammox. We also hypothesized the generation of the potent greenhouse gas nitrous oxide (N2O) during nitrification-denitrification in the presence of Mn-oxides. The microcosms were prepared using sediment sectioned at varying depths (0-2.5, 2.5-4.5, 4.5-8.5, 8.5-12 and 12-17 cm) during two sampling campaigns in October (fall) and January (winter). Labeling with (NO3-)-N-15 revealed low N-2 production originating from NO3- in the water column (P-w), which did not increase significantly on amendment with Mn-oxides during both sampling periods. However, for both seasons, a significant increase of N-2 produced via nitrification (P-n) was observed upon addition of Mn-oxides reaching 76-fold enhancement at <= 2.5 cm. To support these results, sediment slurries of October were subjected to amendment of (NH4+)-N-15, (NO3-)-N-14 with or without addition of Mn-oxides. A substantial production of P15 (N-2 production from (NH4+)-N-15) within 0-17 cm provided further evidence on nitrification-denitrification mediated by Mn-oxides probably with minimal intervention of anammox. In organically rich sediments, anaerobic nitrification-denitrification mediated by Mn-oxides could play an important role in lowering re-mineralized NH4+ levels in the benthic system. As hypothesized, significant production of N2O through the pathway was observed revealing newer mechanisms leading to the generation of the radiative gas.

• 出版日期2015-4