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SPECIATION CHIMIQUE DU FER DANS L'OCEAN : Les complexes fer-porphyrines, méthodes de détection et mécanismes de production

Abstract : Iron bioavailability is a limiting factor for phytoplankton production in many oceanic regions. Dissolved iron (<0.2 µm) consumed by micro-organisms is 99 % complexed by organic ligands whose chemical nature and origins remain poorly understood .

Porphyrins, ubiquist molecules synthetised by all organisms, can chelate iron into iron-porphyrin complexes. When organisms died , those complexes could be released in seawater as products from cellular degradation and could participate to organic complexation of iron. The objective of this work is to test the above hypothesis.

The first part consisted in the development of a first method using a flow injection analysis equipped with chemiluminescence detection (FIA-CL). A protocol was developed for the analysis of seawater samples. Tests of interferences suggested that FIA-CL is specific to iron-porphyrin complexes. Several tests to increase the analytical sensitivity allowed us to reach a detection limit of 0,11 nM equivalent of hemin (iron-porphyrin standard). Thus, first concentrations of iron-porphyrins have been determined in different types of natural environments (seawater, freshwater and intermediate water) rich in organic matter.

The second part consisted in the study of the release of iron-porphyrins in grazing experiments of phytoplankton by zooplankton. In this study, an interference with superoxide radicals generated by the growth of phytoplankton has been found when iron-porphyrins were measured. A protocol of elimination was therefore elaborated to suppress the interference with superoxide radicals. Using culture experiments with a simple model “phytoplankton-zooplankton”, the release of iron-porphyrins in seawater has been demonstrated.

This work will make it possible to study the fate of iron-porphyrins in seawater and their role in organic complexation of iron.
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Contributor : Lilita Vong <>
Submitted on : Wednesday, January 21, 2009 - 3:22:25 PM
Last modification on : Tuesday, October 20, 2020 - 3:10:22 AM
Long-term archiving on: : Tuesday, June 8, 2010 - 6:18:07 PM

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  • HAL Id : tel-00354951, version 1

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Lilita Vong. SPECIATION CHIMIQUE DU FER DANS L'OCEAN : Les complexes fer-porphyrines, méthodes de détection et mécanismes de production. Océan, Atmosphère. Université de la Méditerranée - Aix-Marseille II, 2008. Français. ⟨tel-00354951⟩

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