Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 11, issue 19
Biogeosciences, 11, 5607–5619, 2014
https://doi.org/10.5194/bg-11-5607-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Impact of atmospheric inputs on an oligotrophic ecosystem...

Biogeosciences, 11, 5607–5619, 2014
https://doi.org/10.5194/bg-11-5607-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 14 Oct 2014

Research article | 14 Oct 2014

Microbial food web dynamics in response to a Saharan dust event: results from a mesocosm study in the oligotrophic Mediterranean Sea

E. Pulido-Villena1, A.-C. Baudoux2,*,**, I. Obernosterer3,4, M. Landa3,4, J. Caparros3,4, P. Catala3,4, C. Georges3,4,***, J. Harmand5,6, and C. Guieu7,8 E. Pulido-Villena et al.
  • 1Aix-Marseille Université, Université de Toulon, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, CEDEX 09, France
  • 2Université de Brest; Institut Universitaire Européen de la Mer, IUEM; Laboratoire des Sciences de l'Environnement Marin, UMR 6539 LEMAR, Technopôle Brest Iroise, Copernic, 29280 Plouzané, France
  • 3Sorbonne Universités, UPMC Univ Paris 06, UMR 7621, Laboratoire d'Océanographie Microbienne, 66650 Banyuls/mer, France
  • 4CNRS, UMR 7621, Laboratoire d'Océanographie Microbienne, 66650 Banyuls/mer, France
  • 5Laboratoire de Biotechnologie de l'Environnement-INRA, UR0050, avenue des étangs 11100 Narbonne, France
  • 6MODEMIC research team, UMR MISTEA, SUPAGRO, 2 place Viala 34060 Montpellier CEDEX 2, France
  • 7Laboratoire d'Océanographie de Villefranche/Mer (LOV), CNRS-INSU, UMR7093, Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
  • 8Université Pierre et Marie Curie-Paris 6, UMR 7093, LOV, Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
  • *now at: CNRS, UMR7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France
  • **now at: Sorbonne Universités, UPMC Univ Paris 06, UMR7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France
  • ***now at: Laboratoire d'Océanologie et Géoscience (LOG), UMR CNRS 8187, Université du Littoral Côte d'Opale (ULCO), 32 avenue Foch, 62930 Wimereux, France

Abstract. The significant impact of dust deposition on heterotrophic bacterial dynamics in the surface oligotrophic ocean has recently been evidenced. Considering the central role of bacteria in the microbial loop, it is likely that dust deposition also affects the structure and the functioning of the whole microbial food web. In the frame of the DUNE project, aiming to estimate the impact of dust deposition on the oligotrophic Mediterranean Sea through mesocosm experiments, the main goal of the present paper was to assess how two successive dust deposition events affect the dynamics of the microbial food web. The first dust seeding delivered new P and N to the amended mesocosms and resulted in a pronounced stimulation of bacterial respiration. It also induced pronounced, but transient, changes in the bacterial community composition. No significant effects were observed on the abundances of viruses and heterotrophic nanoflagellates. The second dust seeding also delivered new P and N to the amended mesocosms, but the effect on the microbial food web was very different. Bacterial respiration remained constant and bacterial abundance decreased. Compositional changes following the second seeding were minor compared to the first one. The decrease in bacterial abundance coincided with an increase in virus abundance, resulting in higher virus:bacteria ratios throughout the second seeding period. Our study shows that dust deposition to the surface oligotrophic ocean may involve important modifications of the trophic links among the components of the microbial food web with presumed consequences on C and nutrient cycling.

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