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Modelling of matters fluxes in Marennes-Oléron Bay : coupling hydrodynamics, primary production and oyster consumption |
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To answer the questions of trophic capacity of the oyster bay of Marennes- Oléron, models were implemented since the 90s. The dynamics of the system is studied here by using a model 2D of hydrodynamism and transport with fine meshes (SiAM2D). The modelling and the analysis of existing data are used to answer the following questions: which factors control the primary production in the bay, in which scales of time act these factors, which link exists between pelagic and microphytobenthic productions , and which is the impact of oysters on the planctonic compartment SiAM2D serves as tool to couple models of pelagic and microphytobenthic primary production, and of filtration by oysters. The model of pelagic production is calibrated from measures of productivity realized for the first time on the scale of the bay. These measures show that the production is dependent only on the available light in the column of water. On the scale of year, the model is parametrized by using a limitation by nitrates. The pelagic and microphytobenthic primary productions are the same order on the scale of year. The study of scénarii of consumption and ingestion show that the effect of oysters on Chla is at most 50 %. The various spatiotemporal scales of the processes are defined from the results of modelling, the analysis of data bases and new campaigns of measures. The tide plays an important role in the transport. This bay is characterized by a very short flushing-time and by an East-west dichotomy of functioning. |
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