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| Titel |
Short scale (6 h) temporal variation of sinking fluxes of planktonic and terrigeneous lipids at 200 m in the NW Mediterranean Sea |
| VerfasserIn |
L. Méjanelle, J. Dachs |
| 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 (2009-12-15), S.3017-3034 |
| Datensatznummer |
250004228
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| Publikation (Nr.) |
 copernicus.org/bg-6-3017-2009.pdf |
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| Zusammenfassung |
Drifting sediment trap measurements were carried out at high temporal
frequency in the northwestern Mediterranean Sea in the course of the
DYNAPROC 2 campaign, during the transition between late summer to autumn
conditions. Molecular biomarkers were analyzed in selected subsets of
consecutive samples collected for 6 h at 200 m depth. Fluxes of
n-alkanes, long-chain alkenones, sterols and steroid ketones show high
variability between consecutive 6-h samples, comparable in range to
seasonal variability. n-Alkane export ranges from 1.4 to 29.7μg m−2 d−1,
fluxes of C37 alkenones varies from 0 to 14.2 μg m−2 d−1. Fluxes of sterols, steroid ketones and
C30 alkane diol respectively range from 31 to 377, 2.2 to 46 and 0.3 to
9.3 μg m−2 d−1. Biomarker flux ranges are coherent with the
relatively low primary production and the low export ratio encountered
during the study. Molecular characteristics of biomarker composition is
consistent with reworked algal and zooplanktonic organic matter. Lipid
biomarker composition points to the dominance of haptophytes over
dinoflagellates in the exported material, and to a minor contribution of
diatoms and eustigmatophytes. The intrusion of coastal water at the study
site was recorded by an enhanced imprint of higher plant n-alkanes.
Two processes can be responsible for the pulses in biomarker flux: changes
in the magnitude of particle flux (dry weight mass flux) and changes in the
concentration of biomarkers in the particles.
Concurrent variability in fluxes, significant Pearson correlations between
fluxes of biomarkers of haptophytes, dinoflagellates, eustigmatophytes,
zooplankton activity and higher plants (alkenones, dinosterol, alkyl diols,
dehydrocholesterol, steroid ketones, p<0.01, n=31, suggest that the short
term temporal variability of biomarker export fluxes depends primarily on
the intensity of particle dry weight flux. Biomarker concentrations vary on
a relatively narrower range than biomarker fluxes, indicating that changes
in particle composition (due to degradation or change in source
apportionment) has a weaker influence on flux variability. Thus, particle
aggregation and sinking are key processes to explain the dynamic of
biomarker export at a temporal scale of 6 h. None the less, abrupt
changes of OC-normalized concentrations of biomarkers, in the time scale of
6 h, indicate that the exported particles composition also show
short-time variability. Highest biomarker flux values recorded by the trap
samples from 27 to 29 September correspond to highest values
of zooplankton biomass integrated between the surface and 200 m. The decrease
in primary production after the October wind events is echoed by minima in
biomarker flux values. Despite these correspondences, the coupling between
primary production and biomarker export is complex. |
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