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| Titel |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N2O and CH4 in an upwelling ecosystem |
| VerfasserIn |
L. Farías, C. Fernández, J. Faúndez, M. Cornejo, M. E. Alcaman |
| 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 ; 6, no. 12 ; Nr. 6, no. 12 (2009-12-17), S.3053-3069 |
| Datensatznummer |
250004230
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| Publikation (Nr.) |
 copernicus.org/bg-6-3053-2009.pdf |
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| Zusammenfassung |
| The high availability of electron donors occurring in coastal
upwelling ecosystems with marked oxyclines favours chemoautotrophy,
in turn leading to high N2O and CH4 cycling associated
with aerobic NH4+ (AAO) and CH4 oxidation (AMO). This
is the case of the highly productive coastal upwelling area off
central Chile (36° S), where we evaluated the importance of
total chemolithoautotrophic vs. photoautotrophic production, the
specific contributions of AAO and AMO to chemosynthesis and their
role in gas cycling. Chemolithoautotrophy was studied at a
time-series station during monthly (2007–2009) and seasonal cruises
(January 2008, September 2008, January 2009) and was assessed in
terms of the natural C isotopic ratio of particulate organic carbon
(δ13POC), total and specific (associated with AAO and
AMO) dark carbon assimilation (CA), and N2O and CH4
cycling experiments. At the oxycline, δ13POC averaged
−22.2‰; this was significantly lighter compared to the
surface (−19.7‰) and bottom layers (−20.7‰). Total
integrated dark CA in the whole water column fluctuated between 19.4
and 2.924 mg C m−2 d−1, was higher during active
upwelling, and contributed 0.7 to 49.7% of the total integrated
autotrophic CA (photo plus chemoautotrophy), which ranged from 135
to 7.626 mg C m−2 d−1, and averaged 20.3% for the
whole sampling period. Dark CA was reduced by 27 to 48% after
adding a specific AAO inhibitor (ATU) and by 24 to 76% with GC7,
a specific archaea inhibitor. This indicates that AAO and AMO
microbes (most of them archaea) were performing dark CA through the
oxidation of NH4+ and CH4. Net N2O cycling rates
varied between 8.88 and 43 nM d−1, whereas net CH4
cycling rates ranged from −0.41 to −26.8 nM d−1. The
addition of both ATU and GC7 reduced N2O accumulation and
increased CH4 consumption, suggesting that AAO and AMO were
responsible, in part, for the cycling of these gases. These findings
show that chemically driven chemolithoautotrophy (with NH4+
and CH4 acting as electron donors) could be more important than
previously thought in upwelling ecosystems, raising new questions
concerning its relevance in the future ocean. |
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