Variations des productions de biodépôts (feces et pesudofeces) de l'huître Crassostrea gigas dans un estuaire macrotidal : baie de Marennes-Oléron

The continuous obtention of current (speed and direction) turbidity and phytoplanktonic fluorescence was achieved for 9 successive days during the month of May 1988. Each two hours, during the day, the faeces and pseudofaeces productions of 7 oysters have been sampled individualy. The filtration rate were calculated in continuous. It appeared that the concentration in particular matter and also the planktonic fluorescence fluctuated in direct relation with the water depth, the origin of the water masses and the speed of the wind. During the tidal cycle the mean filtration rate was constant which induced a food consumption largely variable. The oysters were always above the limit of pseudofaeces production which regulated the ingested quantity. Their amount were directly correlated with the concentration of particular matter in suspension. These results demonstrated clearly that a sort of the particular matter occured. The japanese oysters rejected preferentialy the mineraI components in the pseudofaeces while the organic material which went through the digestive tractus was increased.