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(2) A comparative study of the structure (number of species abundance, biomass, trophic groups), operation (web) and the evolution of populations fauna / flora associated with these habitats, with and without oysters (several levels recovery being considered). The sampling will be carried out to characterize the different biocenoses (hard substrates and substrates furniture) in which proliferate each oysters biocoenosis for several sites will be selected to apprehend variability intersites. Different types of exposure to bedrock (housed, semi-housed, beaten) will be taken into account for this characterization of impacts on biodiversity and stand structure.

(3) characterization of the variability of the diet (method of stable isotopes of C and N) in the context of the functional trophic interspecies competition. It is proposed to characterize the isotopic signature oyster Crassostrea gigas and species of crustaceans cirripèdes associated with natural substrates of different sites studied. The hypothesis tested is "competition between these trophic suspension is it constant regardless of the environment trophic?" Test of the influence of seasonality and space.

Results Expected: Identification of the area and carried out ecological definition of potential ecological species on the Channel-Atlantic coasts. Implications in terms of habitats within the meaning of the European Habitats Directive.

Impacts on biodiversity stand structure and food webs. Biotic interactions: Space and trophic competition. Models of ecological succession depending on the intensity of the recovery rates by oysters. Last highlighting process inhibition and facilitation.
Estimation of the role played by C. gigas in the balance sheets of biocalcification intertidal zones on the Atlantic coast of France. Involvement in terms of carbon balance.

The objective here is to test whether the oyster can have an impact similar to that shown for the slipper shell (Ragueneau et al, 2004) in the functioning of ecosystems through their activity filtration and biodéposition. The slipper shell, by its activity filtration and biodéposition, retains a significant share of production in the ecosystem siliceous Rade de Brest, including preventing its export outside the ecosystem (Ragueneau et al, in press). Via the mechanism of recycling, intense during the summer, biogenic silica trapped in the sediment-water interface dissolves and silicates are given to provision of diatoms, to ensure their continued throughout the period productive. It is the proliferation of slipper shell which might have enabled the Rade not switch to blooms of dinoflagellates, often toxic.

The model being developed currently has only the slipper shell filter as important. What is the role of the oyster in the functioning of the ecosystem Rade de Brest? How it intervenes in the balance sheets of nutrients in transit to Rade, at different times of the year?


In addition, the geomorphologic point of view is also to consider. In the first approach, it appears that the proliferation balance, a point of view of balance sheets sedimentary accumulations nearby coastal areas invaded by a strengthening potential and a positive attitude, contributions sedimentary material biogenic. At he geomorphologic therefore is whether the proliferation of oysters may be beneficial in terms of balance sheets sedimentary accumulations to coastal areas affected by the phenomenon invasive.

Interactions with human activities
The theme of the project aims to take stock of various socio-economic and ethnological phenomenon to ask, with the ecological approach, the basis for the integrated management of the problem which is the subject of theme 4.

The case of the proliferation of C. gigas on the Channel-Atlantic coastline is part of this complex pattern, insofar as this proliferation induced effects, partly positive and negative, in part, on various uses for which some are likely market and other non - .
Two types of impacts of the proliferation of C. gigas will be an economic analysis in this project: impacts on market activities; impacts on non-market activities. The goal is 1) to characterize these various impacts, and 2) to the extent possible, quantify them economically with a cost-benefit analysis.

Results expected: characterization of different interactions induced by the proliferation of C. gigas on the uses non-market merchants and coastal areas involved in proliferation. Measures quantitative approach for cost / benefit of the phenomenon.