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| Titel |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
| VerfasserIn |
L. Tremblay, J. Caparros, K. Leblanc, I. Obernosterer |
| 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. 2 ; Nr. 12, no. 2 (2015-01-30), S.607-621 |
| Datensatznummer |
250117793
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| Publikation (Nr.) |
 copernicus.org/bg-12-607-2015.pdf |
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| Zusammenfassung |
| Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters
induces annually occurring spring phytoplankton blooms off the Kerguelen Islands
(Southern Ocean). To examine the origin and fate of particulate and dissolved
organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at
bloom and HNLC stations. Total hydrolyzable AA accounted for 21–25% of
surface particulate organic carbon (%POCAA) at the bloom sites,
but for 10% at the HNLC site. A marked decrease in %POCAA
with depth was observed at the most productive stations leading to values
between 3 and 5% below 300 m depth. AA contributed to only
0.9–4.4% of dissolved organic carbon (%DOCAA) at all
stations. The only consistent vertical trend was observed at the most
productive station (A3-2) where %DOCAA decreased from ~
2% in the surface waters to 0.9% near 300 m. These AA yields
revealed that POM and DOM were more rapidly altered or mineralized at the
bloom sites compared to the HNLC site. Alteration state was also assessed by
trends in C / N ratio, %D-AA and degradation index. Different
molecular markers indicated that POM mostly originated from diatoms and
bacteria. The estimated average proportion of POM from intact phytoplankton
cells in surface waters was 45% at the bloom station A3-2, but 14%
at the HNLC site. Estimates based on D-AA yields indicated that ~
15% of POM and ~ 30% of DOM was of bacterial origin (cells
and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters
appeared less altered than the DOM from the bloom, had slightly higher
dissolved AA concentrations, and showed no sign of alteration within the
water column. Unfavorable conditions for bacterial degradation in HNLC
regions can explain these findings. In contrast, large inputs of labile
organic molecules and iron likely stimulate the degradation of organic
matter (priming effect) and the production of more recalcitrant DOM
(microbial carbon pump) during iron-fertilized blooms. |
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