Impact of dust enrichment on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview

Type Article
Acceptance Date 2021 IN PRESS
Language English
Author(s) Gazeau Frédéric1, Ridame Céline2, Van Wambeke France3, Alliouane Samir1, Stolpe Christian1, Irisson Jean-Olivier1, Marro Sophie1, Grisoni Jean-Michel4, de Liège Guillaume4, Nunige Sandra3, Djaoudi Kahina3, Pulido-Villena Elvira3, Dinasquet Julie5, 6, Obernosterer Ingrid6, Catala Philippe6, Guieu Cécile1
Affiliation(s) 1 : Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, 06230 Villefranche-sur-Mer, France
2 : CNRS-INSU/IRD/MNHN/UPMC, LOCEAN: Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, UMR 7159, 75252 Paris Cedex 05, France
3 : Aix-Marseille Université, Université de Toulon, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, France
4 : Sorbonne Université, CNRS, Institut de la Mer de Villefranche, IMEV, 06230 Villefranche-sur-Mer, France
5 : Scripps Institution of Oceanography, University of California San Diego, USA
6 : CNRS, Sorbonne Université, Laboratoire d'Océanographie Microbienne, LOMIC, F-66650 Banylus-sur-Mer, France
Source Biogeosciences (1726-4189) (Copernicus GmbH) In Press
DOI 10.5194/bg-2020-202
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
Abstract

In Low Nutrient Low Chlorophyll areas, such as the Mediterranean Sea, atmospheric fluxes represent a considerable external source of nutrients likely supporting primary production especially during stratification periods. These areas are expected to expand in the future due to lower nutrient supply from sub-surface waters caused by enhanced stratification, likely further increasing the role of atmospheric deposition as a source of new nutrients to surface waters. Yet, whether plankton communities will react differently to dust deposition in a warmer and acidified environment remains an open question. The impact of dust deposition both in present and future climate conditions was assessed through three perturbation experiments in the open Mediterranean Sea. Climate reactors (300 L) were filled with surface water collected in the Tyrrhenian Sea, Ionian Sea and in the Algerian basin during a cruise conducted in May/June 2017 in the frame of the PEACETIME project. The experimental protocol comprised two unmodified control tanks, two tanks enriched with a Saharan dust analog and two tanks enriched with the dust analog and maintained under warmer (+3 °C) and acidified (−0.3 pH unit) conditions. Samples for the analysis of an extensive number of biogeochemical parameters and processes were taken over the duration of the experiments (3–4 d). Here, we present the general setup of the experiments and the impacts of dust seeding and/or future climate change scenario on nutrients and biological stocks. Dust addition led to a rapid and maximum input of nitrate whereas phosphate release from the dust analog was much smaller. Our results showed that the impacts of Saharan dust deposition in three different basins of the open Northwestern Mediterranean Sea are at least as strong as those observed previously in coastal waters. However, interestingly, the effects of dust deposition on biological stocks were highly different between the three investigated stations and could not be attributed to differences in their degree of oligotrophy but rather to the initial metabolic state of the community. Finally, ocean acidification and warming did not drastically modify the composition of the autotrophic assemblage with all groups positively impacted by warming and acidification, suggesting an exacerbation of effects from atmospheric dust deposition in the future.

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Gazeau Frédéric, Ridame Céline, Van Wambeke France, Alliouane Samir, Stolpe Christian, Irisson Jean-Olivier, Marro Sophie, Grisoni Jean-Michel, de Liège Guillaume, Nunige Sandra, Djaoudi Kahina, Pulido-Villena Elvira, Dinasquet Julie, Obernosterer Ingrid, Catala Philippe, Guieu Cécile Impact of dust enrichment on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview. Biogeosciences IN PRESS. Publisher's official version : https://doi.org/10.5194/bg-2020-202 , Open Access version : https://archimer.ifremer.fr/doc/00688/80015/