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| Titel |
Effects of iron on the elemental stoichiometry during EIFEX and in the diatoms Fragilariopsis kerguelensis and Chaetoceros dichaeta |
| VerfasserIn |
L. J. Hoffmann, I. Peeken, K. Lochte |
| 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 ; 4, no. 4 ; Nr. 4, no. 4 (2007-08-01), S.569-579 |
| Datensatznummer |
250001854
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| Publikation (Nr.) |
 copernicus.org/bg-4-569-2007.pdf |
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| Zusammenfassung |
| The interaction between iron availability and the phytoplankton elemental
composition was investigated during the in situ iron fertilization experiment EIFEX
and in laboratory experiments with the Southern Ocean diatom species
Fragilariopsis kerguelensis and Chaetoceros dichaeta.
Contrary to other in situ iron fertilization experiments we observed an
increase in the BSi:POC, BSi:PON, and BSi:POP ratios within the iron
fertilized patch during EIFEX. This is possibly caused by a relatively
stronger increase in diatom abundance compared to other phytoplankton groups
and does not necessarily represent the amount of silicification of single
diatom cells. In laboratory experiments with F. kerguelensis and C. dichaeta no changes in the POC:PON,
PON:POP, and POC:POP ratios were found with changing iron
availability in both species. BSi:POC, BSi:PON, and BSi:POP ratios
were significantly lower in the high iron treatments compared to the
controls. In F. kerguelensis this was caused by a decrease in cellular BSi concentrations
and therefore possibly less silicification. In C. dichaeta no change in cellular BSi
concentration was found. Here lower BSi:POC, BSi:PON, and BSi:POP
ratios were caused by an increase in cellular C, N, and P under high iron
conditions. These results indicate that iron limitation does not always
increase silicification in diatoms and that changes in the BSi:POC, BSi:PON,
and BSi:POP ratios under iron fertilization in the field are caused
by a variety of different mechanisms. Our results therefore imply that
simple cause-and-effect relationships are not always applicable for modeling
of elemental ratios. |
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