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| Titel |
Effects of the pH/pCO2 control method on medium chemistry and phytoplankton growth |
| VerfasserIn |
D. Shi, Y. Xu, F. M. M. Morel |
| 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 ; 6, no. 7 ; Nr. 6, no. 7 (2009-07-17), S.1199-1207 |
| Datensatznummer |
250003909
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| Publikation (Nr.) |
 copernicus.org/bg-6-1199-2009.pdf |
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| Zusammenfassung |
| The control of key chemical parameters in phytoplankton cultures, such as
pCO2, pH and Ω (the saturation state of calcium carbonate), is
made difficult by the interdependence of these parameters and by the changes
resulting from the growth of the organisms, such as CO2 fixation,
nutrient uptake and, for coccolithophores, calcite precipitation. Even in
cultures where pCO2 or pH is maintained constant, other chemical
parameters change substantially at high cell densities. Experimentally we
observed that various methods of adjustment of pCO2/pH – acid or base
addition, use of buffers or pH-stats, or bubbling of CO2-enriched air
– can be used, the choice of one or the other depending on the goals of the
experiments. At seawater pH, we measured the same growth rates in cultures
of the diatom Thalassiosira weissflogii where the pCO2/pH was controlled by these different
methods. The pH/pCO2 control method also did not affect the rates of
growth or calcification of the coccolithophore Emiliania huxleyi at seawater pH. At lower
pH/higher pCO2, in the E. huxleyi strain PLY M219, we observed increases in rates
of carbon fixation and calcification per cell, along with a slight increase
in growth rate, except in bubbled cultures. In our hands, the bubbling of
cultures seemed to induce more variable results than other methods of
pCO2/pH control. While highly convenient, the addition of pH buffers to
the medium apparently induces changes in trace metal availability and cannot
be used under trace metal-limiting conditions. |
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