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| Titel |
Photosynthate translocation increases in response to low seawater pH in a coral–dinoflagellate symbiosis |
| VerfasserIn |
P. Tremblay, M. Fine, J. F. Maguer, R. Grover, C. Ferrier-Pagès |
| 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. 6 ; Nr. 10, no. 6 (2013-06-18), S.3997-4007 |
| Datensatznummer |
250018297
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| Publikation (Nr.) |
 copernicus.org/bg-10-3997-2013.pdf |
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| Zusammenfassung |
| This study has examined the effect of low seawater pH values (induced by an
increased CO2 partial pressure) on the rates of photosynthesis, as well
as on the carbon budget and carbon translocation in the scleractinian coral
species Stylophora pistillata, using a new model based on
13C labelling of the photosynthetic products. Symbiont photosynthesis
contributes to a large part of the carbon acquisition in tropical coral
species, and it is thus important to know how environmental changes affect
this carbon acquisition and allocation. For this purpose, nubbins of
S. pistillata were maintained for six months at two pHTs (8.1
and 7.2, by bubbling seawater with CO2). The lowest pH value was used to
tackle how seawater pH impacts the carbon budget of a scleractinian coral.
Rates of photosynthesis and respiration of the symbiotic association and of
isolated symbionts were assessed at each pH. The fate of
13C photosynthates was then followed in the symbionts and the coral host
for 48 h. Nubbins maintained at pHT 7.2 presented a lower areal
symbiont concentration, and lower areal rates of gross photosynthesis and
carbon incorporation compared to nubbins maintained at pHT 8.1. The
total carbon acquisition was thus lower under low pH. However, the total
percentage of carbon translocated to the host as well as the amount of
carbon translocated per symbiont cell were significantly higher under
pHT 7.2 than under pHT 8.1 (70% at pHT 7.2 vs.
60% at pHT 8.1), such that the total amount of photosynthetic carbon
received by the coral host was equivalent under both pHs (5.5 to
6.1 μg C cm−2 h−1). Although the carbon budget of the
host was unchanged, symbionts acquired less carbon for their own needs (0.6
compared to 1.8 μg C cm−2 h−1), explaining the overall
decrease in symbiont concentration at low pH. In the long term, such decrease
in symbiont concentration might severely affect the carbon budget of the
symbiotic association. |
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