Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms
The response of N<sub>2</sub> (dinitrogen) fixation to contrasted (wet and dry) Saharan dust deposition was studied in the framework of the DUNE project (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) during which realistic simulations of dust deposition (10 g m<sup&g...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2013-11-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/10/7333/2013/bg-10-7333-2013.pdf |
| _version_ | 1818994840888672256 |
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| author | C. Ridame C. Guieu S. L'Helguen |
| author_facet | C. Ridame C. Guieu S. L'Helguen |
| author_sort | C. Ridame |
| collection | DOAJ |
| description | The response of N<sub>2</sub> (dinitrogen) fixation to contrasted (wet and dry) Saharan dust
deposition was studied in the framework of the DUNE project (a DUst
experiment in a low-Nutrient, low-chlorophyll Ecosystem) during which
realistic simulations of dust deposition (10 g m<sup>−2</sup>) into large mesocosms
(52 m<sup>3</sup>) were performed. Three distinct experimental dust additions were
conducted in June 2008 (DUNE-1-P: simulation of a wet deposition, DUNE-1-Q:
simulation of a dry deposition) and 2010 (DUNE-2-R: simulation of 2
successive wet depositions) in the northwestern oligotrophic Mediterranean
Sea. Here we show that wet and dry dust deposition induced a rapid (24 h or
48 h after dust additions), strong (from 2- to 5.3-fold) and long (at least 4–6 days duration) increase in N<sub>2</sub> fixation, indicating that
both wet and dry Saharan dust deposition was able to relieve efficiently the
nutrient limitation(s) of N<sub>2</sub> fixation. This means in particular that
N<sub>2</sub> fixation activity was not inhibited by the significant input of
nitrate associated with the simulated wet deposition (~ 9 mmol NO<sub>3</sub><sup>−</sup> m<sup>−2</sup>). The input of new nitrogen associated with
N<sub>2</sub> fixation was negligible relative to the atmospheric NO<sub>3</sub><sup>−</sup>
input associated with the dust. The contribution of N<sub>2</sub> fixation to
primary production was negligible (≤ 1%) before and after dust
addition in all experiments, indicating that N<sub>2</sub> fixation was a poor
contributor to the nitrogen demand for primary production. Despite the
stimulation of N<sub>2</sub> fixation by dust addition, the rates remained low,
and did not significantly change the contribution of N<sub>2</sub> fixation to new
production since only a maximum contribution of 10% was observed. The
response of N<sub>2</sub> fixation by diazotrophs and CO<sub>2</sub> fixation by the
whole phytoplankton community suggests that these metabolic processes were
limited or co-limited by different nutrients. With this novel approach, which
allows us to study processes as a function of time while atmospheric particles
are sinking, we show that new atmospheric nutrients associated with Saharan
dust pulses do significantly stimulate N<sub>2</sub> fixation in the Mediterranean
Sea and that N<sub>2</sub> fixation is not a key process in the carbon cycle in
such oligotrophic environments. |
| first_indexed | 2024-12-20T21:04:21Z |
| format | Article |
| id | doaj.art-ea3b1bee0dee467b9b05cad4dc568b90 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-20T21:04:21Z |
| publishDate | 2013-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-ea3b1bee0dee467b9b05cad4dc568b902022-12-21T19:26:39ZengCopernicus PublicationsBiogeosciences1726-41701726-41892013-11-0110117333734610.5194/bg-10-7333-2013Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosmsC. Ridame0C. Guieu1S. L'Helguen2CNRS-INSU/IRD/MNHN/UPMC, LOCEAN: Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, UMR7159, 4 Place Jussieu – 75252 Paris Cedex 05, FranceLOV: Laboratoire d'Océanographie de Villefranche/Mer, CNRS-INSU UMR7093, Observatoire Océanologique, 06230 Villefranche-sur-Mer, FranceUniversité de Brest, CNRS/IRD, UMR6539, Laboratoire des Sciences de l'Environnement Marin, OSU-IUEM, 29280 Plouzané, FranceThe response of N<sub>2</sub> (dinitrogen) fixation to contrasted (wet and dry) Saharan dust deposition was studied in the framework of the DUNE project (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) during which realistic simulations of dust deposition (10 g m<sup>−2</sup>) into large mesocosms (52 m<sup>3</sup>) were performed. Three distinct experimental dust additions were conducted in June 2008 (DUNE-1-P: simulation of a wet deposition, DUNE-1-Q: simulation of a dry deposition) and 2010 (DUNE-2-R: simulation of 2 successive wet depositions) in the northwestern oligotrophic Mediterranean Sea. Here we show that wet and dry dust deposition induced a rapid (24 h or 48 h after dust additions), strong (from 2- to 5.3-fold) and long (at least 4–6 days duration) increase in N<sub>2</sub> fixation, indicating that both wet and dry Saharan dust deposition was able to relieve efficiently the nutrient limitation(s) of N<sub>2</sub> fixation. This means in particular that N<sub>2</sub> fixation activity was not inhibited by the significant input of nitrate associated with the simulated wet deposition (~ 9 mmol NO<sub>3</sub><sup>−</sup> m<sup>−2</sup>). The input of new nitrogen associated with N<sub>2</sub> fixation was negligible relative to the atmospheric NO<sub>3</sub><sup>−</sup> input associated with the dust. The contribution of N<sub>2</sub> fixation to primary production was negligible (≤ 1%) before and after dust addition in all experiments, indicating that N<sub>2</sub> fixation was a poor contributor to the nitrogen demand for primary production. Despite the stimulation of N<sub>2</sub> fixation by dust addition, the rates remained low, and did not significantly change the contribution of N<sub>2</sub> fixation to new production since only a maximum contribution of 10% was observed. The response of N<sub>2</sub> fixation by diazotrophs and CO<sub>2</sub> fixation by the whole phytoplankton community suggests that these metabolic processes were limited or co-limited by different nutrients. With this novel approach, which allows us to study processes as a function of time while atmospheric particles are sinking, we show that new atmospheric nutrients associated with Saharan dust pulses do significantly stimulate N<sub>2</sub> fixation in the Mediterranean Sea and that N<sub>2</sub> fixation is not a key process in the carbon cycle in such oligotrophic environments.http://www.biogeosciences.net/10/7333/2013/bg-10-7333-2013.pdf |
| spellingShingle | C. Ridame C. Guieu S. L'Helguen Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms Biogeosciences |
| title | Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| title_full | Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| title_fullStr | Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| title_full_unstemmed | Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| title_short | Strong stimulation of N<sub>2</sub> fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| title_sort | strong stimulation of n sub 2 sub fixation in oligotrophic mediterranean sea results from dust addition in large in situ mesocosms |
| url | http://www.biogeosciences.net/10/7333/2013/bg-10-7333-2013.pdf |
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