ECOLE DOCTORALE DES SCIENCES DE L
Transcription
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. 1 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 2 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 3