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| Titel |
Response of Nodularia spumigena to pCO2 – Part 2: Exudation and extracellular enzyme activities |
| VerfasserIn |
S. Endres, J. Unger, N. Wannicke, M. Nausch, M. Voss, A. Engel |
| 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. 1 ; Nr. 10, no. 1 (2013-01-29), S.567-582 |
| Datensatznummer |
250017490
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| Publikation (Nr.) |
 copernicus.org/bg-10-567-2013.pdf |
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| Zusammenfassung |
| The filamentous and diazotrophic cyanobacterium Nodularia
spumigena plays a major role in the productivity of the Baltic Sea
as it forms extensive blooms regularly. Under phosphorus limiting conditions
Nodularia spumigena have a high enzyme affinity for
dissolved organic phosphorus (DOP) by production and release of alkaline
phosphatase. Additionally, they are able to degrade proteinaceous compounds
by expressing the extracellular enzyme leucine aminopeptidase. As atmospheric
CO2 concentrations are increasing, we expect marine phytoplankton to
experience changes in several environmental parameters, including pH,
temperature, and nutrient availability. The aim of this study was to
investigate the combined effect of CO2-induced changes in seawater
carbonate chemistry and of phosphate deficiency on the exudation of organic
matter, and its subsequent recycling by extracellular enzymes in a
Nodularia spumigena culture. Batch cultures of
Nodularia spumigena were grown for 15 days under aeration
with low (180 μatm), medium (380 μatm), and high
(780 μatm) CO2 concentrations. Obtained pCO2 levels in
the treatments were on median 315, 353, and 548 μatm CO2,
respectively. Extracellular enzyme activities as well as changes in organic
and inorganic compound concentrations were monitored. CO2
treatment–related effects were identified for cyanobacterial growth, which
in turn influenced the concentration of mucinous substances and the recycling
of organic matter by extracellular enzymes. Biomass production was increased
by 56.5% and 90.7% in the medium and high pCO2 treatment,
respectively, compared to the low pCO2 treatment. In total,
significantly more mucinous substances accumulated in the high pCO2
treatment, reaching 363 μg Xeq L−1 compared to
269 μg Xeq L−1 in the low pCO2 treatment. However,
cell-specific rates did not change. After phosphate depletion, the
acquisition of P from DOP by alkaline phosphatase was significantly enhanced.
Alkaline phosphatase activities were increased by factor 1.64 and 2.25,
respectively, in the medium and high compared to the low pCO2
treatment. We hypothesise from our results that Nodularia
spumigena can grow faster under elevated pCO2 by enhancing
the recycling of organic matter to acquire nutrients. |
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