title: Reduction of the Powerful Greenhouse Gas N2O in the South-Eastern Indian Ocean.
abstract: Nitrous oxide (N2O) is a powerful greenhouse gas and a key catalyst of stratospheric ozone depletion. Yet, little data exist about the sink and source terms of the production and reduction of N2O outside the well-known oxygen minimum zones (OMZ). Here we show the presence of functional marker genes for the reduction of N2O in the last step of the denitrification process (nitrous oxide reductase genes; nosZ) in oxygenated surface waters (180-250 O2 μmol.kg(-1)) in the south-eastern Indian Ocean. Overall copy numbers indicated that nosZ genes represented a significant proportion of the microbial community, which is unexpected in these oxygenated waters. Our data show strong temperature sensitivity for nosZ genes and reaction rates along a vast latitudinal gradient (32°S-12°S). These data suggest a large N2O sink in the warmer Tropical waters of the south-eastern Indian Ocean. Clone sequencing from PCR products revealed that most denitrification genes belonged to Rhodobacteraceae. Our work highlights the need to investigate the feedback and tight linkages between nitrification and denitrification (both sources of N2O, but the latter also a source of bioavailable N losses) in the understudied yet strategic Indian Ocean and other oligotrophic systems.
authors.affiliation: The Oceans Institute, University of Western Australia, M047 35 Stirling Hwy Crawley, 6009 WA, Australia.|CSIRO Oceans and Atmosphere Flagship, Private Bag 5, Wembley, 6913 WA, Australia.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Raes
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, 7001 TAS, Australia.
authors.forename: Levente
authors.initials: L
authors.lastname: Bodrossy
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, 7001 TAS, Australia.
authors.forename: Jodie
authors.initials: J
authors.lastname: Van de Kamp
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, 7001 TAS, Australia.
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Holmes
authors.affiliation: The Oceans Institute, University of Western Australia, M047 35 Stirling Hwy Crawley, 6009 WA, Australia.|CSIRO Oceans and Atmosphere Flagship, Private Bag 5, Wembley, 6913 WA, Australia.
authors.forename: Nick
authors.initials: N
authors.lastname: Hardman-Mountford
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, 7001 TAS, Australia.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Thompson
authors.affiliation: University of Technology, Sydney, Plant Functional Biology & Climate Change, City campus 15 Broadway Ultimo NSW 2007, Australia.
authors.forename: Allison S
authors.initials: AS
authors.lastname: McInnes
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Anya M
authors.initials: AM
authors.lastname: Waite
mesh_terms: D058440:Denitrification; D017752:Greenhouse Effect / Q000517:prevention & control*; D019156:Indian Ocean; D009609:Nitrous Oxide; D010088:Oxidoreductases / Q000235:genetics*; D041902:Rhodobacteraceae / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D014329:Tropical Climate; D014871:Water Microbiology
chemical_list: D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009609:Nitrous Oxide