Trophic interactions between Mytilus chilensis and the toxic dinoflagellate Alexandrium catenella were studied over a 21-day period to determine the absorption kinetics of biochemical components and the enzymatic activity of the digestive gland (i.e. amylase, cellulase complex, laminarinase and protease). For the duration of the experiment, logarithmic relationships were established for the assimilatory balance and carbohydrase activities (amylase, laminarinase and cellulase) of the mussels fed with a toxic diet. The study shows that M. chilensis was able to develop mechanisms which allow exploitation of the toxic microalgae as a food source, despite that its feeding and digestive processes were affected during the first days of contamination.