Uptake and release of paralytic shellfish toxins by the clam Ruditapes decussatus exposed to Gymnodinium catenatum and subsequent depuration

► dcSTX and dcGTX2 + 3 are predominant toxins in clams during exposure and depuration. ► dcSTX and dcGTX2 + 3 show slower depuration rates than C1 + 2. ► Toxin composition of POM points to export of dcSTX by clams. ► Mass balance evidence the gain of dcSTX, dcGTX2 + 3 and dcNEO. ► Gain of decarbamoyl toxins is in line with metabolic interconversion of PSTs.