Modélisation de l'écosystème marin |
1. Description Development of mathematical biogeochemical models coupled with hydrodynamical models [1-7] Mathematical models of marine ecosystems and biogeochemical processes are embedded in 1D and 3D hydrodynamical models. They have been developed for different types of ecosystems: pelagic/benthic, oligotrophic/eutrophicated, open/coastal. The coupled models are used to study the ecosystem functioning, to assess the influence of physical processes on the ecosystem dynamics, to estimate the exchange of biogeochemical components between the coast/shelf and offshore.
Data assimilation: Complexity and performance of ocean biogeochemical and food web models [8-11] Data assimilation has been used in order to improve the performances of biogeochemical models. Two implementations of the Kalman filters have been tested and compared for assimilating biogeochemical data: in [8], a SEEK filter has been used; in [9] an Ensemble filter is described Starting from a complex biogeochemical model, we studied the problem of reduction of the complexity of biogeochemical models in order to obtain more tractable tools for 3D simulations. We are interested in the following questions: 1) how to simplify a complex biogeochemical model (which process can be simplified/ignored) 2) what is the impact of these simplifications on model performances. The reduction of model complexity was investigated using statistical (Empirical Orthogonal Functions) [11], aggregation [10] and data assimilation techniques.
Carbon sequestration by the Ocean To determine whether a region is a source or sink for atmospheric CO2 and understanding the underlying mechanisms require a detailed description of the air-sea CO2 fluxes and their drivers. This requires the collection of field data associated with the modelling of the carbon cycling. We are also particularly interested in modelling the impact of the coccolithophorids on the carbon cycling through calcification/photosynthesis) [12]. Sites under study The test sites are the Black Sea (NATO, EROS21 data, Sesame data) and two areas of the North-western Mediterranean sea: the Ligurian Sea (DYFAMED site) and the Bay of Calvi (Corsica) (STARESO Research station of the Liege University). Models are also developed for mesocosm experiments because mesocosms offer ideal frames for testing mathematical models and in particular, the representation of key-processes thanks to the large data set available. The choice of the different sites will allow comparing very contrasted ecosystems: i) oligotrophic/eutrophicated regions, ii) coastal/deep sea ecosystem, iii) regions influenced by the interactions with benthos (e.g. Bay of Calvi with Posidonia oceanica meadows, a major feature of the coastal environments of the Mediterranean Sea). The presence of coccolithophorids in the Black Sea will allow estimating the impact of potential future shifts in phytoplankton assemblages on carbon export and CO2 uptake by surface waters.
2. Ongoing Projects EU IP project: Southern European Seas (2006-2010): Assessing and Modeling Ecosystem changes (SESAME) The objectives of SESAME are to assess and predict changes in the Mediterranean and Black Sea ecosystems as well as changes in the ability of these ecosystems to provide goods and services. The innovative character of SESAME is reflected in the close merging of economic and natural sciences to study the changes in the western and eastern Mediterranean and the Black Sea within the period from 50 years in the past to 50 years in the future. In the frame of this project, we developed a 3D coupled hydrodynamical- biogeochemical model of the Black Sea focusing on the continental shelf. Mandat d’impulsion scientifique du FNRS « Etude du cycle du carbone dans la zone côtière avec une approche interdisciplinaire intégrant le monitoring in-situ, des modèles mathématiques et l’analyse statistique de données, dans le contexte du changement global ». (http://www.co2.ulg.ac.be/) This project is conducted in collaboration with Jean-Marie Beckers (GHER) and Alberto Borges (Unité d’Océanographie Chimique). The objective was to assess the ability of the coastal zone to sequestrate atmospheric CO2 using mathematical model, field work and statistical tools. Sites under study: the bay of Calvi, the Black Sea shelf, the North Sea, the Ligurian Sea. BelSPo PEACE project “the role of PElagic cAlcification and export of Carbonate production in climate change”. The aim of this project is to study the role in climate regulation of calcification, production and export processes associated to a bloom of the coccolithophorids Emiliania huxleyi. The approach is transdisciplinary combing field and laboratory work and modelling. In this project, we develop a dynamic model describing a bloom of E. huxleyi occurring in a mesocosm experiment [12]. The diversified data set provided by this mesocosm experiment allows testing and validating explicit formulations for key-processes such as calcification, primary production, extra-excretion, TEP formation.
Research Concerted Action of the French Community (2005-2010): “Rapid Assessment of the marine Coastal Environment (RACE)”. The aim of this project is to develop and validate new tools allowing predicting and detecting changes in the Mediterranean coastal ecosystems threatened by human activities. My contribution consists in developing a mathematical model of the seagrass Posidonia oceanica. A linear inverse model has been used in order to reconstruct carbon and nitrogen flows through Posidonia. |
3. Associated people at the Liege University
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4. Collaborations
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5. Selected References 1. Grégoire M., Nezlin N. Kostianoy A., Soetaert K., 2004. Modeling the nitrogen cycling and plankton productivity in an enclosed environment (the Black Sea) using a three-dimensional coupled hydrodynamical-ecosystem model. Journal of Geophysical Research, Vol. 109, C05007, 28p. doi:10.1029/2001JC001014. 2. Grégoire M. and Beckers J.M., 2004. Modeling the nitrogen cycle in an enclosed environment (the Black Sea) : transport versus biogeochemical processes and exchanges across the shelf break, Biogeosciences, 1(1), 30-61, 2004. http://hdl.handle.net/2268/4294. 3. Grégoire M. and Lacroix G., 2003. Exchange Processes and Nitrogen Cycling on the shelf and continental slope of the Black Sea basin, Global Biogeochemical Cycles, 17(2), 42-I – 42-17, doi:10.1029/2002GB001882. 4. Grégoire M. and Friedrich J., 2004. Nitrogen Budget of the north-western Black Sea shelf as inferred from modeling studies and in-situ benthic measurements. Marine Ecology Progress Series, 270, pp. 15 -39. http://www.int-res.com/articles/meps2004/270/m270p015.pdf. 5. Gregoire M; Raick C. and Soetaert K., 2008. Numerical modeling of the deep Black Sea ecosystem functioning during the late 80’s (eutrophication phase, Progress in Oceanography, 76, 3, 286-333. doi:10.1016/j.pocean.2008.01.002. 6. Gregoire M., and Soetaert K., 2010. Nitrogen, Carbon and Sulfur fluxes in the Black Sea as inferred from modelling studies and data, Accepted in Ecological Modeling. 7. Raick C., Delhez E, Soetaert K. and Gregoire M., 2005. Study of the seasonal evolution of the biological productivity of the Ligurian Sea using a 1D coupled hydrodynamical ecosystem model. Journal of Marine Systems, 55, 177 -203. doi:10.1016/j.jmarsys.2004.09.005. 8. Raick C., Alvera A., Brankart JM., Barth A., Soetaert K. and Gregoire M., 2007. Application of a SEEK filter to a 1D biogeochemical model of the Ligurian sea. Journal of Marine Systems, 65(1-4), pp. 561-583 doi:10.1016/j.jmarsys.2005.06.006. 9. Lenartz F. and Raick C. and Soetaert K. and Gregoire M., 2007. Application of an ensemble Kalman Filter to a 1D coupled physical-biological model of the Ligurian sea, Journal of Marine Systems, 68(34), 327-348. http://hdl.handle.net/2268/4584. 10. Raick, Caroline and Soetaert, Karline and Gregoire, Marilaure, 2006. Model complexity and performance: how far can we simplify? Progress in Oceanography, 70(1), pp 27-57. doi:10.1016/j.pocean.2006.03.001. 11. Raick, Caroline and Beckers Jean-Marie and Soetaert Karline and Gregoire Marilaure, 2006. Can Principal Component Analysis be used to predict the dynamics of a strongly non-linear marine biogeochemical model? Ecological Modeling, 196(3-4), 345-364. http://hdl.handle.net/2268/4304. 12. P. Joassin, B. Delille, K. Soetaert, A. V. Borges, L. Chou, A. Engel, J.-P. Gattuso, J. Harlay, U. Riebesell, K. Suykens, and M. Gregoire, 2008. A mathematical modelling of bloom of the coccolithophore Emiliania huxleyi in a mesocosm experiment Biogeosciences Discuss., 5, 787-840, 2008 SRef-ID: 1810-6285/bgd/2008-5-787. |
