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| Titel |
Lack of P-limitation of phytoplankton and heterotrophic prokaryotes in surface waters of three anticyclonic eddies in the stratified Mediterranean Sea |
| VerfasserIn |
T. Tanaka, T. F. Thingstad, U. Christaki, J. Colombet, V. Cornet-Barthaux, C. Courties, J.-D. Grattepanche, A. Lagaria, J. Nedoma, L. Oriol, S. Psarra, M. Pujo-Pay, F. Wambeke |
| 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 ; 8, no. 2 ; Nr. 8, no. 2 (2011-02-28), S.525-538 |
| Datensatznummer |
250005457
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| Publikation (Nr.) |
 copernicus.org/bg-8-525-2011.pdf |
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| Zusammenfassung |
| We investigated the identity of the limiting nutrient of the pelagic
microbial food web in the Mediterranean Sea using nutrient manipulated
microcosms during summer 2008. Experiments were carried out with surface
waters at the center of anticyclonic eddies in the Western Basin, the Ionian
Basin, and the Levantine Basin. In situ, the ratio of N to P was always
higher in both dissolved and particulate organic fractions compared to the
Redfield ratio, suggesting a relative P-starvation. In each experiment, four
different treatments in triplicates (addition of ammonium, phosphate, a
combination of both, and the unamended control) were employed and chemical
and biological parameters monitored throughout a 3–4 day incubation.
Temporal changes of turnover time of phosphate and ATP, and alkaline
phosphatase activity during the incubation suggested that the phytoplankton
and heterotrophic prokaryotes (Hprok) communities were not P-limited at the
sites. Furthermore, statistical comparison among treatments at the end
of the incubation did not support a hypothesis of P-limitation at the three
study sites. In contrast, primary production was consistently limited by N,
and Hprok growth was not limited by N nor P in the Western Basin, but
N-limited in the Ionian Basin, and N and P co-limited in the Levantine Basin.
Our results demonstrated the gap between biogeochemical features (an apparent
P-starved status) and biological responses (no apparent P-limitation). We
question the general notion that Mediterranean surface waters are limited by
P alone during the stratified period. |
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