 |
| Titel |
Strong stimulation of N2 fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms |
| VerfasserIn |
C. Ridame, C. Guieu, S. L'Helguen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-15), S.7333-7346 |
| Datensatznummer |
250085418
|
| Publikation (Nr.) |
 copernicus.org/bg-10-7333-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| The response of N2 (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−2) into large mesocosms
(52 m3) 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 N2 fixation, indicating that
both wet and dry Saharan dust deposition was able to relieve efficiently the
nutrient limitation(s) of N2 fixation. This means in particular that
N2 fixation activity was not inhibited by the significant input of
nitrate associated with the simulated wet deposition (~ 9 mmol NO3− m−2). The input of new nitrogen associated with
N2 fixation was negligible relative to the atmospheric NO3−
input associated with the dust. The contribution of N2 fixation to
primary production was negligible (≤ 1%) before and after dust
addition in all experiments, indicating that N2 fixation was a poor
contributor to the nitrogen demand for primary production. Despite the
stimulation of N2 fixation by dust addition, the rates remained low,
and did not significantly change the contribution of N2 fixation to new
production since only a maximum contribution of 10% was observed. The
response of N2 fixation by diazotrophs and CO2 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 N2 fixation in the Mediterranean
Sea and that N2 fixation is not a key process in the carbon cycle in
such oligotrophic environments. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|