ECOLE DOCTORALE DES SCIENCES DE L

ECOLE DOCTORALE DES SCIENCES DE L’ENVIRONNEMENT
D'ILE DE France N° 129
Proposition de sujet de thèse pour la rentrée 2016
Nom du Laboratoire d’accueil : Laboratoire d’Océanographie de Villefranche (LOV)
N° UMR : 7093
Nom du Directeur du laboratoire : Antoine Sciandra
Adresse complète du laboratoire :
LOV, UMR 7093, Université P&M Curie, Observatoire Océanologique de Villefranche
Station Zoologique, 181 Chemin du Lazaret - 06230, Villefranche-sur-mer, France
Nom de l’Equipe d’accueil et adresse si différente de celle du laboratoire :
Nom du Directeur de thèse HDR :
Cécile Guieu
Téléphone : 04.93.76.39.95
Mail : [email protected]
Nom du co-encadrant non HDR :
Frédéric Gazeau
Téléphone : 04 93 76 38 02
Mail : [email protected]
• Titre de la thèse :
Present and future impact of atmospheric deposition on the structure and functioning of plankton
communities in the Mediterranean Sea (Peacetime project)
• Sujet proposé (2 pages maximum):
Our understanding of the exchange of energy, gas and particles at the ocean–atmosphere interface has
advanced rapidly over the past decade but we remain unable to adequately parameterize fundamental
controlling processes as identified in the new research strategies of the international Surface Ocean–Lower
Atmosphere Study group (SOLAS; Law et al., 2013). A critical bottleneck is the parameterization and
representation of the key processes brought into play by atmospheric deposition in Low Nutrient Low
Chlorophyll (LNLC) regions such as the Mediterranean Sea where the ecosystem functioning may be
modulated by pulsed atmospheric inputs (Guieu et al., 2014). A recent compilation of published studies has
highlighted the heterogeneity of aerosol deposition impacts on biological activity and biogeochemical cycles
in oligotrophic areas (Guieu et al., 2014). Similarly to what is observed in the LNLC Ocean, atmospheric
inputs enhance biological activity in surface waters of the Mediterranean Sea during the stratification period
by relieving the macro- and micro-nutrient limitation. However, different responses have been observed as a
consequence of the deposition pathway (wet or dry), the type of aerosols (natural or anthropogenic) and the
in situ biogeochemical conditions at the time of deposition. In the recent mesocosm ANR DUNE experiment
that was conducted in a Mediterranean coastal area in summer (see Special Issue Biogeoscience,
http://www.biogeosciences.net/special_issue130.html), it has been shown that both structure and functioning
of various biological compartments were impacted by dust deposition.
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The PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea)
project aims at extensively studying and parameterizing the chain of processes occurring in the
Mediterranean Sea after atmospheric deposition, especially of Saharan dust and to put them in perspective of
on-going environmental changes. In the frame of this large project, the specific objectives of this thesis will
be to assess the impact of atmospheric deposition on biogeochemical processes and fluxes in various
trophic regimes and various climate conditions. In the framework of this collaborative project, the PhD
student will be in charge of following the response of the plankton community structure to new nutrients
inputs (nitrogen, iron…) by means of various approaches (ie flow cytometry, pigments), and to evaluate the
potential modifications of its functioning. Plankton community metabolism will be studied through both
oxygen and carbon budgets (following approach from Maugendre et al. 2015a) and the flow of carbon within
the community, as well as its export to deeper layers, will be quantified based on an approach coupling
biomarkers and 13C-labelling (Maugendre et al. 2015b). As both on-going ocean acidification and warming
have been shown to enhance phytoplankton activity under replete nutrient conditions, we will test the
hypothesis whether or not these anthropogenic pressures exacerbate the impacts of nutrient addition from
atmospheric deposition, by conducting experiments both under actual and future conditions of pH and
temperature as projected for the end of the century (IPCC, 2013). Several controlled perturbation
experiments will be performed on board R/V during the PEACETIME cruise (May 2017) but also in the
laboratory where different types of deposited particles will be used (anthropogenic aerosols from pollution,
volcanic ashes etc.) under various environmental conditions. We will use new experimental devices currently
developed at LOV: the minicosms. These are large tanks (300 L) equipped on their top-end with a
combination of LEDs that can be modulated to fully reproduce the sun spectrum and irradiance intensity of
surface Mediterranean waters during the period of investigation. Thanks to an automated sampling design
and to their conical-end shape, minicosms allow following a large number of chemical, biological and
physical parameters and to accurately quantify particle export (ie Bressac and Guieu, 2013). Eight of these
experimental units will be used to follow simultaneously and with a high temporal resolution, the evolution
of biological activity (metabolism, 13C flow), nutrients stocks, dissolved organic matter as well as particles
dynamics and export both under present environmental conditions and following a realistic climate change
scenario (RCP8.5; IPCC 2013).
One of the expected output of the work proposed here is to provide accurate parameterizations of key
biogeochemical processes in order to improve biogeochemical models that will be used in the frame of
PEACETIME. In particular 0-D and 1-D vertical model configuration will be constructed based on the
experimental setup used in the experiments conducted in the frame of the thesis. This will be done in close
collaboration with colleagues from LOCEAN (O. Aumont) and LSCE (JC Dutay), partners of the
PEACETIME project.
Requirements: A candidate with a background in chemical oceanography and field work experience is
sought. Good communication and coordination skills are also required as the experiments will bring together
scientists from several European laboratories.
• Type de Financements prévu autre que ED 129 (CNES, CEA, ADEME etc…) :
This thesis will be conducted in the frame of the PEACETIME project in connection with the national metaprogram MISTRALS (Mediterranean Integrated STudies at Regional And Local Scales; http: // mistralshttp:
// www .mistral-home.org). It is partially funded by this program and cofundings requested to ANR, LEFEGMMC, CNES-TOSCA are currently under evaluation. The campaign planned for May 2017 was ranked
priority 1 by the Comité National de la Flotte Hauturière (CNFH). In this context the research conducted as
part of this thesis are ensured to be realized in the best conditions and with strong collaborations within the
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LOV and other laboratories: Peacetime includes ~ 80 scientists from 16 French lab and 12 abroad. All the
laboratory component teams are implicated in PEACETIME.
• Encadrement :
. Liste des autres doctorants que vous encadrez au 1er janvier 2016 (Nom, Université d’inscription, type
de financement, date de soutenance envisagée)
(Cécile Guieu)
Fabio Benedetti, Univ Paris 6 (bourse KIC Climat) ; soutenance prévue Octobre 2016. (co-encadrement)
References.
Guieu C., O. Aumont, A. Paytan, L. Bopp, C.S. Law, N. Mahowald, E. P. Achterberg, E. Marañón, B.
Salihoglu, A. Crise, T. Wagener, B. Herut, K. Desboeufs, M. Kanakidou, N. Olgun, F. Peters, E.
Pulido-Villena, A. Tovar-Sanchez, C. Völker, 2014, The significance of episodicity in atmospheric
deposition to Low Nutrient Low Chlorophyll regions, Global Biogeochemical Cycles, 2014, DOI:
10.1002/2014GB004852
IPCC, W. G. I. (2013). Contribution to the IPCC Fifth Assessment Report. Climate Change, 36.Bressac M.,
C. Guieu. Post-depositional processes: What really happens to new atmospheric iron in the ocean
surface? Global Biogeochemical Cycles, doi:10.1002/gbc.20076, 2013
Law, C.S., Brévière E., de Leeuw, G., Garçon V., Guieu, C., Kieber, D., Kontradowitz S., Paulmier, A.,
Quinn, P., Saltzman, E., Stefels, J., von Glasow, R., 2013, Evolving Research Directions in Surface
Ocean-Lower Atmosphere (SOLAS) Science, Environmental Chemistry, 10: 1-16
Maugendre L., J.-P. Gattuso, A. J. Poulton, W. Dellisanti, M. Gaubert, C. Guieu and F. Gazeau, No
detectable effect of ocean acidification on plankton metabolism in the NW oligotrophic
Mediterranean Sea: Results from two mesocosm studies, Estuarine Coastal and Shelf Science, 2015a,
in press
Maugendre L, Gattuso JP, de Kluijver A., Soetaert K., van Oevelen D, Middelburg JJ, Gazeau G., Carbon-13
labelling shows no effect of ocean acidification on carbon transfer in Mediterranean plankton
communities, Estuarine Coastal and Shelf Science, 2015b, in press
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