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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-2020-187
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-187
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  23 Jul 2020

23 Jul 2020

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This preprint is currently under review for the journal BG.

Experimental evidence of the potential bioavailability for marine heterotrophic bacteria of aerosols organic matter

Kahina Djaoudi1,2, France Van Wambeke1, Aude Barani1, Najib Bhairy1, Servanne Chevaillier5, Karine Desboeufs5, Sandra Nunige1, Mohammed Labiadh3, Thierry Henry des Tureaux4, Dominique Lefèvre1, Amel Nouara1, Christos Panagiotopoulos1, Marc Tedetti1, and Elvira Pulido-Villena1 Kahina Djaoudi et al.
  • 1Aix-Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
  • 2Molecular and Cellular Biology, The University of Arizona, Tucson, USA
  • 3IRA (Institut des Régions Arides) de Médenine, El Fjé4119, Tunisia
  • 4iEES Paris (Institut d’Ecologie et des Sciences de l’Environnement de Paris), UMR IRD 242, Université Paris Est Créteil-Sorbonne Université-CNRS-INRA-Université de Paris, F-93143 Bondy, France
  • 5LISA, UMR7583, Université de Paris, Université Paris-Est-Créteil, Institut Pierre Simon Laplace (IPSL), Créteil, France

Abstract. The surface ocean receives important amounts of organic carbon from atmospheric deposition. The degree of bioavailability of this source of organic carbon will determine its impact on the marine carbon cycle. In this study, the potential availability of dissolved organic carbon (DOC) leached from both desert dust and anthropogenic aerosols to marine heterotrophic bacteria was investigated. The experimental design was based on 16-days incubation, in the dark, of a marine bacterial inoculum into artificial seawater amended with water-soluble Saharan dust (D-treatment) and anthropogenic (A-treatment) aerosols, so that the initial DOC concentration leachate from aerosols is 36 µM C. Glucose-amended (G) and non-amended (control) treatments were run in parallel. Over the incubation period, an increase in bacterial abundance (BA) and bacterial production (BP) was observed first in the G-treatment, followed then by D and finally A treatments, with bacterial growth rates significantly higher in the G and D treatments than the A treatment. Following this growth, maxima of BP reached were similar in D (879 ± 64 ng C L−1 h−1; n = 3) and G (648 ± 156 ng C L−1 h−1; n = 3) treatments and were significantly higher than in A-treatment (124 ± 39 ng C L−1 h−1; n = 2). The DOC consumed over the incubation period was similar in A (9 ± 4 µM; n = 2) and D (9 ± 2 µM; n = 3) treatments and was significantly lower than that consumed in the G-treatment (22 ± 3 µM). Nevertheless, the bacterial growth efficiency (BGE) in the D treatment (14.2 ± 5.5 %; n = 3) compared well with the G treatment (7.6 ± 2 %; n = 3), suggesting that the metabolic use of the labile DOC fraction in both conditions was energetically equivalent. In contrast, the BGE in the A-treatment was lower (1.7 ± 0.1 %; n = 2), suggesting that the most part of used labile DOC was catabolized. The results obtained in this study highlight the potential of aerosol organic matter to sustain the metabolism of marine heterotrophs and stress the need to include this external source of organic carbon into biogeochemical models, for a better constraining of the carbon budget.

Kahina Djaoudi et al.

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