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| Titel |
Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the KEOPS2 survey |
| VerfasserIn |
F. Carlotti, M.-P. Jouandet, A. Nowaczyk, M. Harmelin-Vivien, D. Lefèvre, P. Richard, Y. Zhu, M. Zhou |
| 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 ; 12, no. 14 ; Nr. 12, no. 14 (2015-07-31), S.4543-4563 |
| Datensatznummer |
250118044
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| Publikation (Nr.) |
 copernicus.org/bg-12-4543-2015.pdf |
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| Zusammenfassung |
This paper presents results on the spatial and temporal distribution
patterns of mesozooplankton in the naturally fertilized region to the east
of the Kerguelen Islands (Southern Ocean) visited at early bloom stage
during the KEOPS2 survey (15 October to 20 November 2011). The aim of this
study was to compare the zooplankton response in contrasted environments
localized over the Kerguelen Plateau in waters of the east shelf and shelf
edge and in productive oceanic deep waters characterized by conditions of
complex circulation and rapidly changing phytoplankton biomass.
The mesozooplankton community responded to the spring bloom earlier on the
plateau than in the oceanic waters, where complex mesoscale circulation
stimulated initial more or less ephemeral blooms before a broader bloom
extension. Taxonomic compositions showed a high degree of similarity across
the whole region, and the populations initially responded to spring bloom
with a large production of larval forms increasing abundances, without
biomass changes. Taxonomic composition and stable isotope ratios of
size-fractionated zooplankton indicated the strong domination of herbivores,
and the total zooplankton biomass values over the survey presented a
significant correlation with the integrated chlorophyll concentrations in
the mixed layer.
The biomass stocks observed at the beginning of the KEOPS2 cruise were around
1.7 g C m−2 above the plateau and 1.2 g C m−2 in oceanic
waters. Zooplankton biomass in oceanic waters remained on average below
2 g C m−2 over the study period, except for one station in the Polar
Front zone (F-L), whereas zooplankton biomasses were around 4 g C m−2
on the plateau at the end of the survey. The most remarkable feature during
the sampling period was the stronger increase in abundance in the oceanic
waters (25 × 103 to 160 × 103 ind m−2)
than on the plateau (25 × 103 to
90 × 103 ind m−2). The size structure and taxonomic
distribution patterns revealed a cumulative contribution of various larval
stages of dominant copepods and euphausiids particularly in the oceanic
waters, with clearly identifiable stages of progress during a Lagrangian time
series survey. The reproduction and early stage development of dominant
species were sustained by mesoscale-related initial ephemeral blooms in
oceanic waters, but growth was still food-limited and zooplankton biomass
stagnated. In contrast, zooplankton abundance and biomass on the shelf were
both in a growing phase, at slightly different rates, due to growth under
sub-optimal conditions. Combined with our observations during the KEOPS1
survey (January–February 2005), the present results deliver a consistent
understanding of patterns in mesozooplankton abundance and biomass from early
spring to summer in the poorly documented oceanic region east of the
Kerguelen Islands. |
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