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| Titel |
Ecosystem function and particle flux dynamics across the Mackenzie Shelf (Beaufort Sea, Arctic Ocean): an integrative analysis of spatial variability and biophysical forcings |
| VerfasserIn |
A. Forest, M. Babin, L. Stemmann, M. Picheral, M. Sampei, L. Fortier, Y. Gratton, S. Bélanger, E. Devred, J. Sahlin, D. Doxaran, F. Joux, E. Ortega-Retuerta, J. Martin, W. H. Jeffrey, B. Gasser, J. Carlos Miquel |
| 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 ; 10, no. 5 ; Nr. 10, no. 5 (2013-05-02), S.2833-2866 |
| Datensatznummer |
250018225
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| Publikation (Nr.) |
 copernicus.org/bg-10-2833-2013.pdf |
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| Zusammenfassung |
| A better understanding of how environmental changes affect organic matter
fluxes in Arctic marine ecosystems is sorely needed. Here we combine
mooring times series, ship-based measurements and remote sensing to assess
the variability and forcing factors of vertical fluxes of particulate
organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a
geospatial model of these fluxes to proceed to an integrative analysis of
their determinants in summer. Flux data were obtained with sediment traps
moored around 125 m and via a regional empirical algorithm applied to
particle size distributions (17 classes from 0.08–4.2 mm) measured by an
Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy
particles) derived from the algorithm (1.26 ± 0.34) and the dominance
(~ 77%) of rapidly sinking small aggregates (< 0.5
mm) in total fluxes suggested that settling material was the product of
recent aggregation processes between marine detritus, gel-like substances,
and ballast minerals. Modeled settling velocity of small and large
aggregates was, respectively, higher and lower than in previous studies
within which a high fractal dimension (i.e., more compact particles) was
consequential of deep-trap collection (~400–1300 m).
Redundancy analyses and forward selection of abiotic/biotic parameters,
linear trends, and spatial structures (i.e., principal coordinates of
neighbor matrices, PCNM) were conducted to partition the variation of the
17 POC flux size classes. Flux variability was explained at 69.5% by the
addition of a temporal trend, 7 significant PCNM, and 9 biophysical
variables. The first PCNM canonical axis (44.5% of spatial variance)
reflected the total magnitude of POC fluxes through a shelf-basin gradient
controlled by bottom depth and sea ice concentration (p < 0.01). The
second most important spatial structure (5.0%) corresponded to areas
where shelf break upwelling is known to occur under easterlies and where
phytoplankton was dominated by diatoms. Among biophysical parameters,
bacterial production and northeasterly wind (upwelling-favorable) were the
two strongest corollaries of POC fluxes (r2 cum. = 0.37). Bacteria
were correlated with small aggregates, while northeasterly wind was
associated with large size classes (> 1 mm ESD), but these two
factors were weakly related with each other. Copepod biomass was overall
negatively correlated (p < 0.05) with vertical POC fluxes, implying
that metazoans acted as regulators of export fluxes, even if their role was
minor given that our study spanned the onset of diapause. Our results
demonstrate that on interior Arctic shelves where productivity is low in
mid-summer, localized upwelling zones (nutrient enrichment) may result in
the formation of large filamentous phytoaggregates that are not
substantially retained by copepod and bacterial communities. |
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