11 Jun 2021

11 Jun 2021

Review status: this preprint is currently under review for the journal BG.

Impact of dust addition on the microbial food web under present and future conditions of pH and temperature

Julie Dinasquet1,2,a, Estelle Bigeard3, Frédéric Gazeau4, Farooq Azam1, Cécile Guieu4, Emilio Marañón5, Céline Ridame6, France Van Wambeke7, Ingrid Obernosterer2, and Anne-Claire Baudoux3 Julie Dinasquet et al.
  • 1Marine Biology Research Division, Scripps Institution of Oceanography, UCSD, USA
  • 2Sorbonne Université, CNRS, Laboratoire d’Océanographie Microbienne, LOMIC, France
  • 3Sorbonne Université, CNRS, Station Biologique de Roscoff, UMR 7144 Adaptation et Diversité en Milieu Marin, France
  • 4Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, 06230 Villefranche-sur-Mer, France
  • 5Department of Ecology and Animal Biology, Universidade de Vigo, Spain
  • 6CNRS-INSU/IRD/MNHN/UPMC, LOCEAN: Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, UMR 7159
  • 7Aix-Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography, UM110, France
  • apresent address: Center for Aerosol Impact on Chemistry of the Environment (CAICE), Scripps Institution of Oceanography, UCSD, USA

Abstract. In the oligotrophic waters of the Mediterranean Sea, during the stratification period, the microbial loop relies on pulsed inputs of nutrients through atmospheric deposition of aerosols from both natural (Saharan dust) and anthropogenic origins. While the influence of dust deposition on microbial processes and community composition is still not fully constrained, the extent to which future environmental conditions will affect dust inputs and the microbial response is not known. The impact of atmospheric wet dust deposition was studied both under present and future (warming and acidification) environmental conditions through experiments in 300 L climate reactors. Three dust addition experiments were performed with surface seawater collected from the Tyrrhenian Sea, Ionian Sea and Algerian basin in the Western Mediterranean Sea during the PEACETIME cruise in May–June 2017. Top-down controls on bacteria, viral processes and community, as well as microbial community structure (16S and 18S rDNA amplicon sequencing) were followed over the 3–4 days experiments. Different microbial and viral responses to dust were observed rapidly after addition and were most of the time higher when combined to future environmental conditions. The input of nutrients and trace metals changed the microbial ecosystem from bottom-up limited to a top-down controlled bacterial community, likely from grazing and induced lysogeny. The composition of mixotrophic microeukaryotes and phototrophic prokaryotes was also altered. Overall, these results suggest that the effect of dust deposition on the microbial loop is dependent on the initial microbial assemblage and metabolic state of the tested water, and that predicted warming, and acidification will intensify these responses, affecting food web processes and biogeochemical cycles.

Julie Dinasquet et al.

Status: open (until 23 Jul 2021)

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Julie Dinasquet et al.

Data sets

Gazeau, F., Ridame, C., Van Wambeke, F., Alliouane, S., Stolpe, C., Irisson, J.-O., Marro, S., Grisoni, J.-M., De Liège, G., Nunige, S., Djaoudi, K., Pulido-Villena, E., Dinasquet, J., Obernosterer, I., Catala, P., and Guieu, C. Impact of dust enrichment on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview

Impact of dust addition on the metabolism of Mediterranean plankton communities and carbon export under present and future conditions of pH and temperature, Biogeosciences Discuss. Gazeau, F., Van Wambeke, F., Marañón, E., Pérez-Lorenzo, M., Alliouane, S., Stolpe, C., Blasco, T., Leblond, N., Zäncker, B., Engel, A., Marie, B., Dinasquet, J., and Guieu, C.

Julie Dinasquet et al.


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Short summary
Saharan dust deposition of nutrients and trace metals is crucial to microbes in the Mediterranean Sea. Here, we tested the response of microbial and viral communities to simulated dust deposition, under present and future conditions of temperature and pH. Overall, the effect of deposition was dependent on the initial microbial assemblage, and future conditions will intensify microbial responses. We observed effects on trophic interactions cascading all the way down to viral processes.