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| Titel |
The effects of nutrient additions on particulate and dissolved primary production and metabolic state in surface waters of three Mediterranean eddies |
| VerfasserIn |
A. Lagaria, S. Psarra, D. Lefèvre, F. Wambeke, C. Courties, M. Pujo-Pay, L. Oriol, T. Tanaka, U. Christaki |
| 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. 9 ; Nr. 8, no. 9 (2011-09-14), S.2595-2607 |
| Datensatznummer |
250006123
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| Publikation (Nr.) |
 copernicus.org/bg-8-2595-2011.pdf |
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| Zusammenfassung |
| We examined the effects of nutrient additions on rates of 14C-based
particulate and dissolved primary production as well as O2-based
metabolic rates in surface waters (8 m) of three anticyclonic eddies,
located in the Western, Central and Eastern Mediterranean. Ship-board
microcosm experiments employing additions of inorganic nitrogen (+N) and
phosphorus (+P), alone and in combination (+NP), were conducted in June/July
2008 during the BOUM (Biogeochemistry from the Oligotrophic to the
Ultra-oligotrophic Mediterranean) cruise. In all three experiments,
particulate primary production was significantly stimulated by the additions
of nitrogen (+N, +NP) while no effect was observed with the addition of
phosphorus alone (+P). Percent extracellular release of photosynthate (PER)
displayed the lowest values (4–8 %) in the +NP treatment. Among the three
treatments (+N, +P, +NP), the +NP had the strongest effect on oxygen
metabolic rates, leading to positive values of net community production
(NCP > 0). These changes of NCP were mainly due to enhanced gross primary
production (GPP) rather than reduced dark community respiration rates (DCR).
In all three sites, in +NP treatment autotrophic production (whether
expressed as GPP or PPtotal) was sufficient to fulfil the
estimated carbon requirements of heterotrophic prokaryotes, while addition
of nitrogen alone (+N) had a weaker effect on GPP, resulting in
metabolically balanced systems. At the three sites, in treatments with N
(+N, +NP), phytoplankton and heterotrophic prokaryote production were
positively correlated. Heterotrophic conditions were observed in the Control
and +P treatment at the central and eastern sites, and autotrophic
production was not sufficient to supply estimated bacterial carbon demand,
evidence of a decoupling of phytoplankton production and consumption by
heterotrophic prokaryotes. |
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