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| Titel |
Size distribution of particles and zooplankton across the shelf-basin system in southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows |
| VerfasserIn |
A. Forest, L. Stemmann, M. Picheral, L. Burdorf, D. Robert, L. Fortier, M. Babin |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2012-04-10), S.1301-1320 |
| Datensatznummer |
250006944
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| Publikation (Nr.) |
 copernicus.org/bg-9-1301-2012.pdf |
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| Zusammenfassung |
| The size distribution and mean spatial trends of large particles (>100 μm, in equivalent spherical diameter, ESD) and mesozooplankton were
investigated across the Mackenzie Shelf (southeast Beaufort Sea, Arctic
Ocean) in July–August 2009. Our main objective was to combine results from
an Underwater Vision Profiler 5 (UVP5) and traditional net tows (200 μm
mesh size) to characterize the structural diversity and functioning of the
Arctic shelf-basin ecosystem and to assess the large-scale correspondence
between the two methodological approaches. The core dataset comprised 154
UVP5 profiles and 29 net tows conducted in the shelf (<100 m isobath),
slope (100–1000 m) and basin (>1000 m) regions of the study area. The mean
abundance of total particles and zooplankton in the upper water column
(<75 m depth) declined exponentially with increasing distance from shore.
Vertical and latitudinal patterns in total particle concentration followed
those of chlorophyll a (chl a) concentration, with maximum values between 30
and 70 m depth. Based on the size-spectra derived from the UVP5 dataset,
living organisms (0.1–10 mm ESD) accounted for an increasingly large
proportion of total particle abundance (from 0.1 % to >50 %) when
progressing offshore and as the ESD of particles was increasing. Both the
UVP5 and net tows determined that copepods dominated the zooplankton
community (~78–94 % by numbers) and that appendicularians were
generally the second most abundant group (~1–11 %). The vertical
distribution patterns of copepods and appendicularians indicated a close
association between primary production and the main grazers. Manual
taxonomic counts and ZooScan image analyses shed further light on the
size-structure and composition of the copepod community – which was
dominated at ~95 % by a guild of 10 typical taxa. The size
distributions of copepods, as evaluated with the 3 methods (manual counts,
ZooScan and UVP5), showed consistent patterns co-varying in the same order
of magnitude over the upper size range (>1 mm ESD). Copepods <1 mm were
not well quantified by the UVP5, which estimated that only ~13–25 %
of the assemblage was composed of copepods <1 mm ESD compared with ~77–89 %
from the net tow estimates. However, the biovolume of copepods
was overwhelmingly dominated (~93–97 %) by copepods >1 mm ESD. Our
results illustrate that the combination of traditional sampling methods and
automated imaging techniques is a powerful approach that enabled us to
conclude on the prevalence of a relatively high productivity regime and
dominant herbivorous food web over the shelf when compared with the
low-productive recycling system detected offshore. |
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