The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate

Peter K Swart, S. Evans, T. Capo, M. A. Altabet

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

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 -.

Original languageEnglish (US)
Pages (from-to)6147-6157
Number of pages11
JournalBiogeosciences
Volume11
Issue number21
DOIs
StatePublished - Nov 13 2014

Fingerprint

nitrogen isotope
oxygen isotope
macroalgae
isotopes
fractionation
nitrates
nitrate
oxygen
algae
nitrogen
Agardhiella
experiment
isotope fractionation
alga
syringes
Ulva
pumps
stable isotopes
assimilation
pump

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes

Cite this

The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate. / Swart, Peter K; Evans, S.; Capo, T.; Altabet, M. A.

In: Biogeosciences, Vol. 11, No. 21, 13.11.2014, p. 6147-6157.

Research output: Contribution to journalArticle

Swart, Peter K ; Evans, S. ; Capo, T. ; Altabet, M. A. / The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate. In: Biogeosciences. 2014 ; Vol. 11, No. 21. pp. 6147-6157.
@article{b2ebb7deb6e84a169374fd5724e61dd5,
title = "The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate",
abstract = "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 -.",
author = "Swart, {Peter K} and S. Evans and T. Capo and Altabet, {M. A.}",
year = "2014",
month = "11",
day = "13",
doi = "10.5194/bg-11-6147-2014",
language = "English (US)",
volume = "11",
pages = "6147--6157",
journal = "Biogeosciences",
issn = "1726-4170",
publisher = "European Geosciences Union",
number = "21",

}

TY - JOUR

T1 - The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate

AU - Swart, Peter K

AU - Evans, S.

AU - Capo, T.

AU - Altabet, M. A.

PY - 2014/11/13

Y1 - 2014/11/13

N2 - 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 -.

AB - 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 -.

UR - http://www.scopus.com/inward/record.url?scp=84961291541&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84961291541&partnerID=8YFLogxK

U2 - 10.5194/bg-11-6147-2014

DO - 10.5194/bg-11-6147-2014

M3 - Article

AN - SCOPUS:84961291541

VL - 11

SP - 6147

EP - 6157

JO - Biogeosciences

JF - Biogeosciences

SN - 1726-4170

IS - 21

ER -