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| Titel |
Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different pCO2 levels in a mesocosm study |
| VerfasserIn |
T. Tanaka, T. F. Thingstad, T. Løvdal, H.-P. Grossart, A. Larsen, M. Allgaier, M. Meyerhöfer, K. G. Schulz, J. Wohlers, E. Zöllner, U. Riebesell |
| 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. 3 ; Nr. 5, no. 3 (2008-05-06), S.669-678 |
| Datensatznummer |
250002513
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| Publikation (Nr.) |
 copernicus.org/bg-5-669-2008.pdf |
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| Zusammenfassung |
| Availability of phosphate for phytoplankton and bacteria and of glucose for
bacteria at different pCO2 levels were studied in a mesocosm experiment
(PeECE III). Using nutrient-depleted SW Norwegian fjord waters, three
different levels of pCO2 (350 μatm: 1×CO2; 700 μatm:
2×CO2; 1050 μatm: 3×CO2) were set up, and nitrate and
phosphate were added at the start of the experiment in order to induce a
phytoplankton bloom. Despite similar responses of total particulate P concentration and phosphate turnover time at the three different pCO2
levels, the size distribution of particulate P and 33PO4 uptake
suggested that phosphate transferred to the >10 μm fraction was
greater in the 3×CO2 mesocosm during the first 6–10 days when phosphate
concentration was high. During the period of phosphate depletion (after Day
12), specific phosphate affinity and specific alkaline phosphatase activity
(APA) suggested a P-deficiency (i.e. suboptimal phosphate supply) rather
than a P-limitation for the phytoplankton and bacterial community at the
three different pCO2 levels. Specific phosphate affinity and specific
APA tended to be higher in the 3×CO2 than in the 2×CO2 and
1×CO2 mesocosms during the phosphate depletion period, although no
statistical differences were found. Glucose turnover time was correlated
significantly and negatively with bacterial abundance and production but not
with the bulk DOC concentration. This suggests that even though constituting
a small fraction of the bulk DOC, glucose was an important component of
labile DOC for bacteria. Specific glucose affinity of bacteria behaved
similarly at the three different pCO2 levels with measured specific
glucose affinities being consistently much lower than the theoretical
maximum predicted from the diffusion-limited model. This suggests that
bacterial growth was not severely limited by the glucose availability.
Hence, it seems that the lower availability of inorganic nutrients after the
phytoplankton bloom reduced the bacterial capacity to consume labile DOC in
the upper mixed layer of the stratified mesocosms. |
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