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| Titel |
CO2 increases 14C primary production in an Arctic plankton community |
| VerfasserIn |
A. Engel, C. Borchard, J. Piontek, K. G. Schulz, U. Riebesell, R. Bellerby |
| 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. 3 ; Nr. 10, no. 3 (2013-03-01), S.1291-1308 |
| Datensatznummer |
250018124
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| Publikation (Nr.) |
 copernicus.org/bg-10-1291-2013.pdf |
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| Zusammenfassung |
Responses to ocean acidification in plankton communities were studied during
a CO2-enrichment experiment in the Arctic Ocean, accomplished from June
to July 2010 in Kongsfjorden, Svalbard (78°56′ 2′′ N, 11°53′ 6′′ E). Enclosed in 9 mesocosms (volume: 43.9–47.6 m3),
plankton was exposed to CO2 concentrations, ranging from glacial to
projected mid-next-century levels. Fertilization with inorganic nutrients at
day 13 of the experiment supported the accumulation of phytoplankton
biomass, as indicated by two periods of high chl a concentration.
This study tested for CO2 sensitivities in primary production (PP) of
particulate organic carbon (PPPOC) and of dissolved organic carbon
(PPDOC). Therefore, 14C-bottle incubations (24 h) of
mesocosm samples were performed at 1 m depth receiving about 60% of
incoming radiation. PP for all mesocosms averaged 8.06 ± 3.64 μmol C L−1 d−1 and was slightly higher than in the outside fjord
system. Comparison between mesocosms revealed significantly higher
PPPOC at elevated compared to low pCO2 after nutrient addition.
PPDOC was significantly higher in CO2-enriched mesocosms before as
well as after nutrient addition, suggesting that CO2 had a direct
influence on DOC production. DOC concentrations inside the mesocosms
increased before nutrient addition and more in high CO2 mesocosms.
After addition of nutrients, however, further DOC accumulation was
negligible and not significantly different between treatments, indicating
rapid utilization of freshly produced DOC. Bacterial biomass production (BP)
was coupled to PP in all treatments, indicating that 3.5 ± 1.9% of
PP or 21.6 ± 12.5% of PPDOC provided on average sufficient carbon for
synthesis of bacterial biomass. During the later course of the
bloom, the response of 14C-based PP rates to CO2 enrichment
differed from net community production (NCP) rates that were also determined
during this mesocosm campaign. We conclude that the enhanced release
of labile DOC during autotrophic production at high CO2 exceedingly stimulated activities of heterotrophic microorganisms.
As a consequence, increased PP induced less NCP, as suggested earlier for
carbon-limited microbial systems in the Arctic. |
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