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| Titel |
High temperature decreases the PIC / POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta) |
| VerfasserIn |
A. C. Gerecht, L. Šupraha, B. Edvardsen, I. Probert, J. Henderiks |
| 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 ; 11, no. 13 ; Nr. 11, no. 13 (2014-07-03), S.3531-3545 |
| Datensatznummer |
250117503
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| Publikation (Nr.) |
 copernicus.org/bg-11-3531-2014.pdf |
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| Zusammenfassung |
| Rising ocean temperatures will likely increase stratification of the water
column and reduce nutrient input into the photic zone. This will increase the
likelihood of nutrient limitation in marine microalgae, leading to changes in
the abundance and composition of phytoplankton communities, which in turn
will affect global biogeochemical cycles. Calcifying algae, such as
coccolithophores, influence the carbon cycle by fixing CO2 into
particulate organic carbon through photosynthesis (POC production) and into
particulate inorganic carbon through calcification (PIC production). As
calcification produces a net release of CO2, the ratio of PIC to POC
production determines whether coccolithophores act as a source (high PIC / POC)
or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of
phosphorus (P-) limitation and high temperature on the physiology and the
PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large
and heavily calcified species is a major contributor to calcite export from
the photic zone into deep-sea reservoirs. Phosphorus limitation did not
influence exponential growth rates in either subspecies, but P-limited cells
had significantly lower cellular P-content. One of the subspecies was
subjected to a 5 °C temperature increase from 10 °C to
15 °C, which did not affect exponential growth rates either, but
nearly doubled cellular P-content under both high and low phosphate
availability. This temperature increase reduced the PIC / POC ratio by
40–60%, whereas the PIC / POC ratio did not differ between P-limited and
nutrient-replete cultures when the subspecies were grown near their
respective isolation temperature. Both P-limitation and elevated temperature
significantly increased coccolith malformations. Our results suggest that a
temperature increase may intensify P-limitation due to a higher P-requirement
to maintain growth and POC production rates, possibly reducing abundances in
a warmer ocean. Under such a scenario C. pelagicus may decrease its
calcification rate relative to photosynthesis, thus favouring
CO2 sequestration over release. It seems unlikely that P-limitation by
itself causes changes in the PIC / POC ratio in this species. |
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