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Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones.

Kalvelage T, Lavik G, Jensen MM, Revsbech NP, Löscher C, Schunck H, Desai DK, Hauss H, Kiko R, Holtappels M, LaRoche J, Schmitz RA, Graco MI, Kuypers MM - PLoS ONE (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany.

ABSTRACT
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.

No MeSH data available.


Physicochemical zonation and rates of microbial respiration in the OMZs off Namibia and Peru.(a-c) Namibian shelf (station 252, 111m). (d-f) Peruvian coastal OMZ (station 807, 115 m). (g-i) Offshore Peruvian OMZ (station 3, 4697 m). Dashed lines indicate the upper OMZ boundary (O2 ≤15 μmol l-1). Previously determined rates of aerobic and anaerobic NH4+ oxidation [14,24,25] are tenfold magnified. Please note the differences in scale between stations. *Chlorophyll a concentrations in panel b in relative units.
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pone.0133526.g001: Physicochemical zonation and rates of microbial respiration in the OMZs off Namibia and Peru.(a-c) Namibian shelf (station 252, 111m). (d-f) Peruvian coastal OMZ (station 807, 115 m). (g-i) Offshore Peruvian OMZ (station 3, 4697 m). Dashed lines indicate the upper OMZ boundary (O2 ≤15 μmol l-1). Previously determined rates of aerobic and anaerobic NH4+ oxidation [14,24,25] are tenfold magnified. Please note the differences in scale between stations. *Chlorophyll a concentrations in panel b in relative units.

Mentions: The stations investigated on the Namibian shelf (19°S-23°S) were characterized by high surface chlorophyll a concentrations, i.e. high primary productivity, at the time of sampling [25]. Oxygen concentrations in the surface waters ranged from ~150 to 250 μmol l-1 and gradually declined to ≤15 μmol l-1 (here used as a cut-off for the upper OMZ boundary) at ~65–85 m depth (Fig 1a and S1 Fig). At two sampling sites (station 225 and 252), steep O2 gradients in the upper OMZ as well as non-detectable levels of O2 (≤100 nmol l-1) by STOX sensor measurements in the lower OMZ (S1 Table), indicated apparently anoxic conditions over the shelf. In contrast, O2 concentrations in the lower micromolar range (~2–6 μmol l-1) persisted throughout the OMZ at nearby stations (231 and 243). Both O2 and density gradients indicated a rather weak stratification of the Namibian shelf waters, facilitating vertical mixing of more oxygenated surface waters into the OMZ.


Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones.

Kalvelage T, Lavik G, Jensen MM, Revsbech NP, Löscher C, Schunck H, Desai DK, Hauss H, Kiko R, Holtappels M, LaRoche J, Schmitz RA, Graco MI, Kuypers MM - PLoS ONE (2015)

Physicochemical zonation and rates of microbial respiration in the OMZs off Namibia and Peru.(a-c) Namibian shelf (station 252, 111m). (d-f) Peruvian coastal OMZ (station 807, 115 m). (g-i) Offshore Peruvian OMZ (station 3, 4697 m). Dashed lines indicate the upper OMZ boundary (O2 ≤15 μmol l-1). Previously determined rates of aerobic and anaerobic NH4+ oxidation [14,24,25] are tenfold magnified. Please note the differences in scale between stations. *Chlorophyll a concentrations in panel b in relative units.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4507870&req=5

pone.0133526.g001: Physicochemical zonation and rates of microbial respiration in the OMZs off Namibia and Peru.(a-c) Namibian shelf (station 252, 111m). (d-f) Peruvian coastal OMZ (station 807, 115 m). (g-i) Offshore Peruvian OMZ (station 3, 4697 m). Dashed lines indicate the upper OMZ boundary (O2 ≤15 μmol l-1). Previously determined rates of aerobic and anaerobic NH4+ oxidation [14,24,25] are tenfold magnified. Please note the differences in scale between stations. *Chlorophyll a concentrations in panel b in relative units.
Mentions: The stations investigated on the Namibian shelf (19°S-23°S) were characterized by high surface chlorophyll a concentrations, i.e. high primary productivity, at the time of sampling [25]. Oxygen concentrations in the surface waters ranged from ~150 to 250 μmol l-1 and gradually declined to ≤15 μmol l-1 (here used as a cut-off for the upper OMZ boundary) at ~65–85 m depth (Fig 1a and S1 Fig). At two sampling sites (station 225 and 252), steep O2 gradients in the upper OMZ as well as non-detectable levels of O2 (≤100 nmol l-1) by STOX sensor measurements in the lower OMZ (S1 Table), indicated apparently anoxic conditions over the shelf. In contrast, O2 concentrations in the lower micromolar range (~2–6 μmol l-1) persisted throughout the OMZ at nearby stations (231 and 243). Both O2 and density gradients indicated a rather weak stratification of the Namibian shelf waters, facilitating vertical mixing of more oxygenated surface waters into the OMZ.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Biogeochemistry Department, Max Planck Institute for Marine Microbiology, Bremen, Germany.

ABSTRACT
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.

No MeSH data available.