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| Titel |
Activity and abundance of denitrifying bacteria in the subsurface biosphere of diffuse hydrothermal vents of the Juan de Fuca Ridge |
| VerfasserIn |
A. Bourbonnais, S. K. Juniper, D. A. Butterfield, A. H. Devol, M. M. M. Kuypers, G. Lavik, S. J. Hallam, C. B. Wenk, B. X. Chang, S. A. Murdock, M. F. Lehmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-22), S.4661-4678 |
| Datensatznummer |
250007403
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| Publikation (Nr.) |
 copernicus.org/bg-9-4661-2012.pdf |
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| Zusammenfassung |
| Little is known about fixed nitrogen (N) transformation and elimination at
diffuse hydrothermal vents where anoxic fluids are mixed with oxygenated
crustal seawater prior to discharge. Oceanic N sinks that remove
bio-available N ultimately affect chemosynthetic primary productivity in
these ecosystems. Using 15N paired isotope techniques, we determined
potential rates of fixed N loss pathways (denitrification, anammox) and
dissimilatory nitrate reduction to ammonium (DNRA) in sulfidic hydrothermal
vent fluids discharging from the subsurface at several sites at Axial Volcano
and the Endeavour Segment on the Juan de Fuca Ridge. We also measured
physico-chemical parameters (i.e., temperature, pH, nutrients, H2S and
N2O concentrations) as well as the biodiversity and abundance of
chemolithoautotrophic nitrate-reducing, sulfur-oxidizing γ-proteobacteria (SUP05 cluster) using sequence analysis of amplified small
subunit ribosomal RNA (16S rRNA) genes in combination with taxon-specific
quantitative polymerase chain reaction (qPCR) assays. Denitrification was the
dominant N loss pathway in the subsurface biosphere of the Juan de Fuca
Ridge, with rates of up to ~1000 nmol N l−1 day−1. In
comparison, anammox rates were always < 5 nmol N l−1 day−1
and below the detection limit at most of the sites. DNRA rates were up to
~150 nmol N l−1 day−1. These results suggest that
bacterial denitrification out-competes anammox in sulfidic hydrothermal vent
waters. Taxon-specific qPCR revealed that γ-proteobacteria of the
SUP05 cluster sometimes dominated the microbial community (SUP05/total
bacteria up to 38%). Significant correlations were found between fixed
N loss (i.e., denitrification, anammox) rates and in situ nitrate and
dissolved inorganic nitrogen (DIN) deficits in the fluids, indicating that
DIN availability may ultimately regulate N loss in the subsurface. Based on
our rate measurements, and on published data on hydrothermal fluid fluxes and
residence times, we estimated that up to ~10 Tg N yr−1 could
globally be removed in the subsurface biosphere of hydrothermal vents
systems, thus, representing a small fraction of the total
marine N loss (~275 to > 400 Tg N yr−1). |
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