PSP detoxification kinetics in the mussel Mytilus galloprovincialis. One- and two-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 distributed into different body tissues which have varying affinities for them, and later these toxins are transferred by the bivalves to other trophic levels. After the disappearance of the toxic cells, shellfish remain toxic for a variable period of time, depending on the detoxification kinetics. We studied these kinetics in mussels Mytilus galloprovincialis previously exposed to a bloom of the PSP producing dinoflagellate Gymnodinium catenatum. The toxin profile observed in the mussels was very similar to that of G. catenatum, showing that toxin transformations (chemical or enzymatic) had little or no importance in this case. The detoxification rates at all the sampling points decreased progressively from ca 0.25 to 0 d-1 following an inverse hyperbolic-like curve. These rates were related to different degrees to the environmental factors studied (salinity, temperature, and light transmission as a measure of seston volume, and in vivo fluorescence as a measure of phytoplankton concentration) and to fresh body weight during each sampling period (estimated by multiple regression). In general, detoxification rates became increasingly independent of the variables cited as the experiment progressed. One- and 2-compartment detoxification models, both with 2 variants (with fixed and variable detoxification rates depending on the environmental variables and body weight), were used to describe the detoxification kinetics observed. Neither of the 2 variants of the 1-compartment models correctly described detoxification. The 2-compartment models, on the other hand, particularly the environmentally controlled variant, fit the observed detoxification kinetics very well. There was only a slight difference between these last 2 models, which would suggest that the actual effect of the environmental variables considered in the detoxification process is unimportant.

Peer reviewed