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

Type Article
Acceptance Date 2021-01 IN PRESS
Language English
Author(s) Dinasquet JulieORCID1, 2, Bigeard Estelle3, Gazeau FrédéricORCID4, Azam Farooq1, Guieu CécileORCID4, Marañón EmilioORCID5, Ridame Céline6, Van Wambeke France7, Obernosterer Ingrid2, Baudoux Anne-Claire3
Affiliation(s) 1 : Marine Biology Research Division, Scripps Institution of Oceanography, UCSD, USA
2 : Sorbonne Université, CNRS, Laboratoire d’Océanographie Microbienne, LOMIC, France
3 : Sorbonne Université, CNRS, Station Biologique de Roscoff, UMR 7144 Adaptation et Diversité en Milieu Marin, France
4 : Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, 06230 Villefranche-sur-Mer, France
5 : Department of Ecology and Animal Biology, Universidade de Vigo, Spain
6 : CNRS-INSU/IRD/MNHN/UPMC, LOCEAN: Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, UMR 7159
7 : Aix-Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography, UM110, France
Source Biogeosciences (1726-4170) (Copernicus GmbH) In Press
DOI 10.5194/bg-2021-143
Note Special issue : Atmospheric deposition in the low-nutrient-low-chlorophyll (LNLC) ocean: effects on marine life today and in the future (BG/ACP inter-journal SI) Editor(s): Christine Klaas, Cecile Guieu, Karine Desboeufs, Jan-Berend Stuut, Mark Moore, Paraskevi Pitta, Silvia Becagli, and Chiara Santinelli Special issue jointly organized between Biogeosciences and Atmospheric Chemistry and Physics
Keyword(s) bacteria, microeukaryotes, virus, community composition, top-down

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.

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Dinasquet Julie, Bigeard Estelle, Gazeau Frédéric, Azam Farooq, Guieu Cécile, Marañón Emilio, Ridame Céline, Van Wambeke France, Obernosterer Ingrid, Baudoux Anne-Claire Impact of dust addition on the microbial food web under present and future conditions of pH and temperature. Biogeosciences IN PRESS. Publisher's official version : , Open Access version :