PSP DETOXIFICATION KINETICS IN THE MUSSEL MYTILUS-GALLOPROVINCIALIS -ONE-COMPARTMENT AND 2-COMPARTMENT MODELS AND THE EFFECT OF SOME ENVIRONMENTAL VARIABLES

Paralytic shellfish poisoning (PSP) toxins are accumulated by bivalves during toxic plankton blooms. In these bivalves the toxins are distri buted into different body tissues which have varying affinities for th em, and later these toxins are transferred by the bivalves to other tr ophic levels. After the disappearance of the toxic cells, shellfish re main toxic for a variable period of time, depending on the detoxificat ion kinetics. We studied these kinetics in mussels Mytilus galloprovin cialis previously exposed to a bloom of the PSP producing dinoflagella te Gymnodinium catenatum. The toxin profile observed in the mussels wa s very similar to that of G, calenatum, showing that toxin transformat ions (chemical or enzymatic) had Little or no importance in this case. The detoxification rates at all the sampling points decreased progres sively from ca 0.25 to 0 d(-1) following an inverse hyperbolic-like cu rve. These rates were related to different degrees to the environmenta l factors studied (salinity, temperature, and light transmission as a measure of seston volume, and in vivo fluorescence as a measure of phy toplankton concentration) and to fresh body weight during each samplin g period (estimated by multiple regression). In general, detoxificatio n rates became increasingly independent of the variables cited as the experiment progressed. One-and 2-compartment detoxification models, bo th with 2 variants (with fixed and variable detoxification rates depen ding on the environmental variables and body weight), were used to des cribe the detoxification kinetics observed. Neither of the 2 variants of the l-compartment models correctly described detoxification. The 2- compartment models, on the other hand, particularly the environmentall y controlled variant, fit the observed detoxification kinetics very we ll. There was only a slight difference between these last 2 models, wh ich would suggest that the actual effect of the environmental variable s considered in the detoxification process is unimportant.