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| Titel |
The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate |
| VerfasserIn |
P. K. Swart, S. Evans, T. Capo, M. A. Altabet |
| 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. 21 ; Nr. 11, no. 21 (2014-11-13), S.6147-6157 |
| Datensatznummer |
250117672
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| Publikation (Nr.) |
 copernicus.org/bg-11-6147-2014.pdf |
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| Zusammenfassung |
| In order to determine and understand the stable isotope fractionation of
18O and 15N manifested during assimilation of NO3− in
marine macro-benthic algae, two species (Ulva sp. and
Agardhiella sp.) have been grown in a wide range of NO3−
concentrations (2–500 μM). Two types of experiments were
performed. The first was one in which the concentration of the NO3−
was allowed to drift downward as it was assimilated by the algae, between 24
hour replacements of media. These experiments proceeded for periods of
between 7 and 10 days. A second set of experiments maintained the
NO3− concentration at a low steady-state value by means of a syringe
pump. The effective fractionation during the assimilation of the NO3−
was determined by measuring the δ15N of both the (i) new algal
growth and (ii) residual NO3− in the free-drift experiments after 0,
12, 24 and 48 h. Modelling these data show that the fractionation during
assimilation is dependent upon the concentration of NO3− and is
effectively 0 at concentrations of less than ~2 μM. The
change in the fractionation with respect to concentration is the greatest at
lower concentrations (2–10 μM). The fractionation stablizes
between 4 and 6‰ at concentrations of between 50 and 500 μM.
Although the δ18O and δ15N values of NO3− in the
residual solution were correlated, the slope of relationship also varied with
respect to NO3− concentration, with slopes of greater than unity at
low concentration. These results suggest shifts in the dominant fractionation
mechanism of 15N and 18O between concentrations of 1 and
10 μM NO3−. At higher NO3− concentrations
(>10–50 μM), fractionation during assimilation will lead to
δ15N values in algal biomass lower than the ambient NO3−
and 15N enrichments in the residual NO3−. |
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