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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2017-129
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-2017-129
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Submitted as: research article 19 May 2017

Submitted as: research article | 19 May 2017

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Organic exudates promote Fe(II) oxidation in Fe limited cultures of Trichodesmium erythraeum

Hanieh T. Farid1, Kai G. Schulz2, and Andrew L. Rose1,3 Hanieh T. Farid et al.
  • 1Southern Cross Geoscience, Southern Cross University, Lismore 2480, Australia
  • 2Centre for Coastal Biogeochemistry, School of Environment, Science and Engineering, Southern Cross University, Lismore NSW, 2480, Australia
  • 3School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia

Abstract. A luminol chemiluminescence method was employed to study the oxidation kinetics of Fe(II) in both the absence and the presence of organic exudates released by the marine cyanobacterium Trichodesmium erythraeum. The apparent Fe(II) oxidation rate constant was studied for batch cultures grown with varying Fe' concentrations of 0.05–0.29 and 1.44–2.03 nmol L−1 at pH ranges from 8.1–8.6, corresponding to the change in pH in the cultures during the entire growth cycle. Fe(II) oxidation was accelerated when cells were growing exponentially and gradually decreased towards the stationary phase, consistent with the presence of organic exudates. The best fit of the kinetic model to the data also demonstrated clear differences in apparent Fe(II) oxidation rate constants during different growth phases. However, no significant difference was observed in oxidation rate constants between the two Fe' treatments. These findings suggest that Trichodesmium releases organic compounds into the extracellular environment that influence Fe redox chemistry, potentially affecting Fe bioavailability, and that the nature of the Fe(II) complexes formed is not influenced by Fe limitation of the organism's growth.

Hanieh T. Farid et al.
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Hanieh T. Farid et al.
Hanieh T. Farid et al.
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Short summary
This study provides new insights into: (a) how organic exudates from a marine cyanobacterium may influence iron speciation and bioavailability in the extracellular milieu; and (b) approaches for evaluating rate constants for Fe(II) oxidation in the presence of unknown organic ligands. Given that microorganisms play critical roles in biochemical cycling of trace metals in water systems, the findings are expected to improve nutrient uptake models and be of interest to broad range of readers.
This study provides new insights into: (a) how organic exudates from a marine cyanobacterium may...
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