Reduction of the Powerful Greenhouse Gas N2O in the South-Eastern Indian Ocean

Eric J Raes; Levente Bodrossy; Jodie Van de Kamp; Bronwyn Holmes; Nick Hardman-Mountford; Peter A Thompson; Allison S McInnes; Anya M Waite

doi:10.1371/journal.pone.0145996

Reduction of the Powerful Greenhouse Gas N2O in the South-Eastern Indian Ocean

PLoS One. 2016 Jan 22;11(1):e0145996. doi: 10.1371/journal.pone.0145996. eCollection 2016.

Authors

Eric J Raes^{1

2}, Levente Bodrossy³, Jodie Van de Kamp³, Bronwyn Holmes³, Nick Hardman-Mountford^{1

2}, Peter A Thompson³, Allison S McInnes⁴, Anya M Waite⁵

Affiliations

¹ The Oceans Institute, University of Western Australia, M047 35 Stirling Hwy Crawley, 6009 WA, Australia.
² CSIRO Oceans and Atmosphere Flagship, Private Bag 5, Wembley, 6913 WA, Australia.
³ CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, 7001 TAS, Australia.
⁴ University of Technology, Sydney, Plant Functional Biology & Climate Change, City campus 15 Broadway Ultimo NSW 2007, Australia.
⁵ Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.

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.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Denitrification
Greenhouse Effect / prevention & control*
Indian Ocean
Nitrous Oxide*
Oxidoreductases / genetics*
Rhodobacteraceae / genetics
Seawater / microbiology*
Tropical Climate
Water Microbiology

Substances

Oxidoreductases
nitrous oxide reductase
Nitrous Oxide

Grants and funding

E. J. Raes received an Australian Postgraduate scholarship from the University of Western Australia and a CSIRO Wealth from Oceans postgraduate top-up scholarship.