Preprints
https://doi.org/10.5194/bg-2020-20
https://doi.org/10.5194/bg-2020-20

  31 Jan 2020

31 Jan 2020

Review status: this preprint was under review for the journal BG but the revision was not accepted.

Oxygen and light determine the pathways of nitrate reduction in a highly saline lake

Nicolás Valiente1,2, Franz Jirsa3,4, Thomas Hein5,6, Wolfgang Wanek7, Patricia Bonin8, and Juan José Gómez-Alday2 Nicolás Valiente et al.
  • 1Centre for Biogeochemistry in the Anthropocene, Department of Biosciences, Section for Aquatic Biology and Toxicology, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway
  • 2Biotechnology and Natural Resources Section, Institute for Regional Development (IDR), University of Castilla–La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain
  • 3Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria
  • 4Department of Zoology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006 Johannesburg, South Africa
  • 5WasserCluster Lunz – Inter-university Center for Aquatic Ecosystem Research, Lunz am See, Dr. Carl Kupelwieser Prom. 5, 3293 Lunz/See, Austria
  • 6Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Gregor-Mendel-Str. 33, 1180 Vienna, Austria
  • 7Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
  • 8Aix-Marseille Université, CNRS, Université de Toulon, IRD, MIO UMR 110, 13288 Marseille, France

Abstract. Nitrate (NO3) removal from aquatic ecosystems involves several microbially mediated processes including denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonium oxidation (anammox) regulated by slight changes in environmental gradients. Saline lakes are prone to the accumulation of anthropogenic contaminants, making them highly vulnerable environments to NO3 pollution. We investigated nitrate removal pathways in mesocosm experiments using lacustrine, undisturbed, organic-rich sediments from Pétrola Lake (Spain), a highly saline waterbody subject to anthropogenic NO3 pollution. We used the revised 15N-isotope pairing technique (15N-IPT) to determine NO3 sink processes. Our results demonstrate the coexistence of denitrification, DNRA, and anammox processes, and their contribution was determined by environmental conditions (oxygen and light). DNRA and N2O-denitrification were the dominant nitrogen (N) removal pathways when oxygen and/or light were present (up to 82 %). In contrast, anoxia and darkness promoted NO3 reduction by DNRA (52 %) and N loss by anammox (28 %). Our results highlight the role of coupled DNRA-anammox, as yet has never been investigated in hypersaline lake ecosystems. We conclude that anoxia and darkness favored DNRA and anammox processes over denitrification and therefore reduce N2O emissions to the atmosphere.

Nicolás Valiente et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Nicolás Valiente et al.

Nicolás Valiente et al.

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Short summary
Saline lakes are prone to the accumulation of anthropogenic contaminants, making them highly vulnerable environments to nitrate pollution. We used the revised 15N-isotope pairing technique with sediments from a eutrophic hypersaline lake to unravel the nitrate removal pathways carrying on. Our work shows for the first time the coexistence of denitrification, DNRA and anammox in a highly saline/hypersaline lake, with extraordinarily high rates of coupled DNRA-anammox.
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