A seasonal source and sink of nitrous oxide in mangroves: Insights from concentration, isotope, and isotopomer measurements. (1st October 2018)

• Record Type: Journal Article
• Authors: Murray, Rachel; Erler, Dirk; Rosentreter, Judith; Maher, Damien; Eyre, Bradley
• Is Part Of: Geochimica et cosmochimica acta. Volume 238(2018)
• Page Start: 169
• Page End: 192
• Publication Date: 2018-10-01
• Subjects: Nitrous oxide -- Mangrove -- Estuary -- Isotope -- Isotopomer -- Fungal denitrification -- Nitrogen; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2018.07.003
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: Mangrove forests can be a source or a sink of nitrous oxide (N2 O) to the atmosphere, but seasonal mangrove N2 O dynamics are not well understood. We used continuous high-resolution N2 O concentration data to construct seasonal budgets of N2 O in two tropical mangrove-lined creeks for both the wet and dry seasons. Furthermore we used N stable isotope analysis to constrain the pathways of N2 O production and consumption within these creeks. Calculated water-air fluxes were within a range typical of undisturbed mangroves, however obvious seasonal differences in N2 O dynamics were observed at the two sites. The mangrove systems were a net source of N2 O to the atmosphere during the dry season and a net sink during the wet season. In the wet season we propose that increased allochthonous carbon enhances N2 O consumption by denitrification. Combining the seasonal fluxes, the Fitzroy mangrove system, which received a continual input of allochthonous nitrate (NO3 − ), was a net source of N2 O, while the Burdekin mangrove system was close to a net N2 O balance. Interpreted in the context of DIN and N2 O concentrations, the N2 O isotopic values observed in the dry season point to fungal denitrification as the most likely pathway of N2 O production. This study shows that subtle shifts in seasonal nutrient supply regulate mangrove N2 O production and consumption.