CONTAMINATION KINETICS OF MUSSELS MYTILUS -EDULIS EXPOSED TO A NATURAL-POPULATION OF DINOFLAGELLATES DINOPHYSIS SPP

In June 1.992, two batches of mussels were submerged ten days off the Strait of Antioche, on the French Atlantic coast, respectively (1) in subsurface water where the concentration of Dinophysis spp. remained b elow 100 cells. l-1 during the first week and then sharply increased u p to near 3 000 cells. l-1, and (2) in the thermocline where Dinophysi s spp. concentration first ranged between 100 and 1000 cells. l-1 and then was slightly more than 3 000 cells. l-1. The presence of okadaic acid (0.A.) was not detected during one week in mussels feeding in sur face water, whereas those in the thermocline contained 2.7 mug.g-1 O.A . in digestive gland (dry weight). At the end of the experiment, musse ls of both batches contained circa 63 mug.g-1. It is concluded (1) tha t mussel contamination is very fast as soon as Dinophysis spp, density is higher than 1000 cell. l-1 (2) that the toxicity threshold for hum an safety can be reached in two or three days, and (3) that the weekly toxin analysis stated as a minimum survey during warning periods meet s the limit of frequency for a reliable detection of poisoned-mussel a reas.