Modelling domoic acid retention in Argopecten purpuratus and Pecten maximus: Comparison of dynamics in fast and slow depurators

As filter feeders, pectinid bivalves are susceptible to accumulate domoic acid (DA), a neurotoxin produced by diatoms of genus Pseudo-nitzschia and responsible for the Amnesic Shellfish Poisoning. The transfer of DA to higher trophic levels presents a health risk, leading to the closure of fisheries and aquaculture exploitation when concentrations exceed regulatory thresholds. Therefore, this can be a significant socioeconomic concern. Some species, such as Pecten maximus , show prolonged retention, whereas others, such as Argopecten purpuratus , depurate much faster. The physiological mechanisms underlying these differences are not yet fully understood. This study developed a bioenergetic model coupled with a toxin kinetics module to describe DA dynamics. By calibrating the species-specific elimination rate, the model accurately simulated DA depuration in both scallop species under laboratory and field conditions. Our findings reveal that dilution by growth is an important mechanism to be considered for species with a long-term DA depuration, as it accounts for a significant portion of total toxin removal, particularly in small individuals. However, for commercial-sized scallops this dilution still contributes up to 55% of total depuration. The depuration rate appears to be independent of body size, suggesting that the observed temporal inversion of the correlation between DA concentration and body size is primarily driven by growth dilution. The model also suggests that the interindividual variability observed after a seven-month depuration period could stem from differences in feeding behaviour and elimination rates. Further experimental validation is needed to confirm or refute these hypotheses regarding individual life traits.