Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein.
Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany;Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany;Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany;Department of Biological Sciences, University of Aarhus, Aarhus, Denmark;Institute for General Microbiology, Christian Albrechts University Kiel, Kiel, Germany;Institute for General Microbiology, Christian Albrechts University Kiel, Kiel, Germany;GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany;GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;Institute for General Microbiology, Christian Albrechts University Kiel, Kiel, Germany;Dirección de Investigaciones Oceanográficas, Instituto del Mar del Perú, Lima, Peru;Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany
Recommended Citation:
Tim Kalvelage,Gaute Lavik,Marlene M. Jensen,et al. Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones[J]. PLOS ONE,2015-01-01,10(7)