Étude des interactions entre les processus physiques et biologiques intervenant dans la production de l’huître creuse Crassostrea gigas (Thunberg) du bassin Marennes-Oléron : essais de modélisation.

A deterministic model of nutrition and growth behaviour of the japanese oyster Crassostrea gigas is built using experimental and field data, and validated by field measurements. Its integration in a model that couple primary production and horizontal transport of suspended matter and nutrients permits to study the Charente river flow influence on the biotic capacity of Marennes-Oléron Bay. The oysters growth rate is positively correlated with the nitrate input variations. However, the oyster growth sensivity to nitrate input variations is proved to depend both on mollusk location and age. In a second step, the effect of the oyster stock on primary and secondary production is evaluated. Spatial variability of oyster growth response is clearly shown. The greatest sensivity of the oysters located southward underlines the north-south phytoplancton depletion by molluscs. Interactions between oyster production and environment is also examined using a model integrating the vertical exchanges of particulate matter (sedimentation, resuspension) in the particulate transport calculation. The vertical exchange model is calibrated on field data. Interim results point out a quite important effect of these exchanges on turbidity simulation on a spatial and temporal scale. In that situation, the oysters growth model shows a decrease of biotic capacity (of the Basin) and subsquently a decresase of growth sensivity to stock variation that is stronger in the central area oyster production.