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A dual-labeling method for the simultaneous measurement of dissolved inorganic carbon and phosphate uptake by marine planktonic species


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Titre de la revue : Limnology and Oceanography : Methods Volume : 4 Pagination : 416-425 Date de publication : 01/10/2006

Type de document > *Article de revue

Mots clés >

Unité de recherche > IRSN/DEI/SECRE/LRE

Auteurs > DUHAMEL Solange, MOUTIN Thierry, ZEMAN Florence

Date de publication > 01/12/2006

Résumé

The measurement of primary production is the foundation for aquatic biogeochemistry research. The biogeochemical cycles of phosphate (P) and other biolimiting elements are tightly linked to marine primary production. We have optimized an existing method of carbon (C) and P dual isotope labelling to study the simultaneous C and P uptake by plankton species in marine environments. The two main objectives of this study were (1) to test the preservation properties of the labelled samples and the calculation methods used in separating the signals of the different radionuclides, and (2) to adapt the method to marine environments. The procedure was successfully implemented in contrasting locations within the South East Pacific (between 146.36°W and 72.49°W). The uptake rates determined using this method ranged from 14 to 900 nM h-1 for dissolved inorganic C and from 0.03 to 4.5 nM h-1 for dissolved inorganic P in surface water. The detection limit found in ultraoligotrophic surface water was of 3.33 nM h-1 and 0.01 nM h-1 for C and P respectively. C and P assimilation fluxes in low and high productivity open-ocean systems may be studied using this sensitive method. We outline a protocol for marine environments that is appropriate for use under oceanographic cruise conditions. Results from the application of this method will lead to a better understanding of the interplay between carbon and phosphate biogeochemical cycles in the upper ocean.