Article (Scientific journals)
Annual nitrogen budget of the seagrass Posidonia oceanica as determined by in situ uptake experiments
Lepoint, Gilles; Millet, S.; Dauby, Patrick et al.
2002In Marine Ecology. Progress Series, 237, p. 87-96
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Keywords :
seagrass; nitrogen uptake; N-15 tracer; NW Mediterranean
Abstract :
[en] The uptake of nitrate and ammonium by the roots and leaves of Posidonia oceanica were determined between February 1993 and June 1999 by in situ experiments using the isotope 15 of nitrogen (N-15) as a tracer in a nutrient-poor coastal zone of the NW Mediterranean Sea (Revellata Bay, Corsica). Nitrate and ammonium leaf uptakes are recorded at 0.05 and 0.1 muM respectively. The high variability observed cannot be explained solely by the variation of the substrate concentrations in the water column. For leaves, mean specific uptake rates were 43 +/- 45 and 43 +/- 64 mug N g N-1 h(-1). Nitrate and ammonium leaf uptake fluxes (g N m(-2) yr(-1)) seem to have the same importance on an annual basis. :Nitrate uptake occurs mainly in winter and early spring, when nitrate concentrations in the water column are highest. The uptake of N, and mainly of ammonium, is significant throughout the year with maxima at the beginning of spring, but it is insufficient to meet the annual N requirement of the plant. Posidonia root biomass was very high and corresponded to high specific N uptake rates by the roots. Ammonium was incorporated by the roots 6 times faster than nitrate. In the sediment, this uptake capacity is limited by the nutrient diffusion rate, and the root uptake is therefore insufficient to meet the N requirements of the plant. In fact, P. oceanica of Revellata Bay have a complex N budget involving uptake and recycling processes and allowing the plants to meet their N requirements in one of the most nutrient-poor areas of the NW Mediterranean Sea. We calculated that leaf and root would contribute to 40 and 60% of the annual N uptake, respectively, and 60% of the annual N requirement of the plant.
Research center :
MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
Disciplines :
Aquatic sciences & oceanology
Environmental sciences & ecology
Earth sciences & physical geography
Author, co-author :
Lepoint, Gilles  ;  Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Océanologie
Millet, S.
Dauby, Patrick ;  Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Systématique et diversité animale
Gobert, Sylvie  ;  Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Océanologie
Bouquegneau, Jean-Marie ;  Université de Liège - ULiège > Département des sciences et gestion de l'environnement > Océanologie
Language :
English
Title :
Annual nitrogen budget of the seagrass Posidonia oceanica as determined by in situ uptake experiments
Publication date :
18 July 2002
Journal title :
Marine Ecology. Progress Series
ISSN :
0171-8630
eISSN :
1616-1599
Publisher :
Inter-Research, Oldendorf Luhe, Germany
Volume :
237
Pages :
87-96
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
FRIA - Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture [BE]
FWB - Fédération Wallonie-Bruxelles [BE]
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since 25 November 2008

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