Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem
The high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N<sub>2</sub>O and CH<sub>4</sub> cycling associated with aerobic NH<sub>4</sub><sup>+</sup> (AAO)...
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2009-12-01
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doaj-79547cbd048f4c7bb3984726514cce1d2020-11-24T21:12:12ZengCopernicus PublicationsBiogeosciences1726-41701726-41892009-12-0161230533069Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystemM. E. AlcamanM. CornejoJ. FaúndezC. FernándezL. FaríasThe high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N<sub>2</sub>O and CH<sub>4</sub> cycling associated with aerobic NH<sub>4</sub><sup>+</sup> (AAO) and CH<sub>4</sub> 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 (δ<sup>13</sup>POC), total and specific (associated with AAO and AMO) dark carbon assimilation (CA), and N<sub>2</sub>O and CH<sub>4</sub> cycling experiments. At the oxycline, δ<sup>13</sup>POC 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<sup>−2</sup> d<sup>−1</sup>, 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<sup>−2</sup> d<sup>−1</sup>, 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 NH<sub>4</sub><sup>+</sup> and CH<sub>4</sub>. Net N<sub>2</sub>O cycling rates varied between 8.88 and 43 nM d<sup>−1</sup>, whereas net CH<sub>4</sub> cycling rates ranged from −0.41 to −26.8 nM d<sup>−1</sup>. The addition of both ATU and GC7 reduced N<sub>2</sub>O accumulation and increased CH<sub>4</sub> consumption, suggesting that AAO and AMO were responsible, in part, for the cycling of these gases. These findings show that chemically driven chemolithoautotrophy (with NH<sub>4</sub><sup>+</sup> and CH<sub>4</sub> acting as electron donors) could be more important than previously thought in upwelling ecosystems, raising new questions concerning its relevance in the future ocean. http://www.biogeosciences.net/6/3053/2009/bg-6-3053-2009.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
M. E. Alcaman M. Cornejo J. Faúndez C. Fernández L. Farías |
spellingShingle |
M. E. Alcaman M. Cornejo J. Faúndez C. Fernández L. Farías Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem Biogeosciences |
author_facet |
M. E. Alcaman M. Cornejo J. Faúndez C. Fernández L. Farías |
author_sort |
M. E. Alcaman |
title |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem |
title_short |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem |
title_full |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem |
title_fullStr |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem |
title_full_unstemmed |
Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem |
title_sort |
chemolithoautotrophic production mediating the cycling of the greenhouse gases n<sub>2</sub>o and ch<sub>4</sub> in an upwelling ecosystem |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2009-12-01 |
description |
The high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N<sub>2</sub>O and CH<sub>4</sub> cycling associated with aerobic NH<sub>4</sub><sup>+</sup> (AAO) and CH<sub>4</sub> 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 (δ<sup>13</sup>POC), total and specific (associated with AAO and AMO) dark carbon assimilation (CA), and N<sub>2</sub>O and CH<sub>4</sub> cycling experiments. At the oxycline, δ<sup>13</sup>POC 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<sup>−2</sup> d<sup>−1</sup>, 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<sup>−2</sup> d<sup>−1</sup>, 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 NH<sub>4</sub><sup>+</sup> and CH<sub>4</sub>. Net N<sub>2</sub>O cycling rates varied between 8.88 and 43 nM d<sup>−1</sup>, whereas net CH<sub>4</sub> cycling rates ranged from −0.41 to −26.8 nM d<sup>−1</sup>. The addition of both ATU and GC7 reduced N<sub>2</sub>O accumulation and increased CH<sub>4</sub> consumption, suggesting that AAO and AMO were responsible, in part, for the cycling of these gases. These findings show that chemically driven chemolithoautotrophy (with NH<sub>4</sub><sup>+</sup> and CH<sub>4</sub> acting as electron donors) could be more important than previously thought in upwelling ecosystems, raising new questions concerning its relevance in the future ocean. |
url |
http://www.biogeosciences.net/6/3053/2009/bg-6-3053-2009.pdf |
work_keys_str_mv |
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