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| Titel |
Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific |
| VerfasserIn |
R. Sempéré, M. Tedetti, C. Panagiotopoulos, B. Charrière, F. Wambeke |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2008-08-25), S.1165-1173 |
| Datensatznummer |
250002686
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| Publikation (Nr.) |
 copernicus.org/bg-5-1165-2008.pdf |
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| Zusammenfassung |
| The distribution and bacterial availability of dissolved neutral sugars were
studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise.
Four contrasting stations were investigated: Marquesas Islands (MAR), the
hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre
(EGY), and the coastal waters associated to the upwelling area off Chile
(UPW). Total (free and combined) dissolved neutral sugar (TDNS)
concentrations were in the same order of magnitude at MAR (387±293 nM),
GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with
the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY
(250 m, 58 nM), respectively. Their contribution to dissolved organic carbon
(TDNS-C×DOC−1%) was generally low for all sites varying
from 0.4% to 6.7% indicating that South East Pacific surface waters
were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS;
e.g. sugars analyzed without hydrolysis) concentrations were very low within
the detection limit of our method (5–10 nM) accounting for <5% of the
TDNS. In general, the predominant sugars within the TDNS pool were glucose,
xylose, arabinose, and galactose, while in the FDNS pool only glucose was
present. TDNS stock to bacterial production ratios (integrated values from
the surface to the deep chlorophyll maximum) were high at GYR with respect
to the low primary production, whereas the opposite trend was observed in
the highly productive area of UPW. Intermediate situations were observed for
MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to
natural solar radiation was also experimentally studied and compared to dark
treatments. Our results showed no or little detectable effect of sunlight on
DOM bacterial assimilation in surface waters of UPW and GYR, while a
significant stimulation was found in MAR and EGY. The overall results
clearly suggest that DOM is less labile at GYR compared to UPW, which is
consistent with the observed accumulation of dissolved organic carbon and
the elevated C/N ratios reported by Raimbault et al. (2008). |
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