Alexandrium catenella (Group I) Causes Higher and Faster Toxicity Than A. pacificum (Group IV) in Mytilus eduis

Consuming poisoned shellfish can lead to severe health problems and even death. Alexandrium catenella (Group I) and A. pacificum (Group IV) cause paralytic shellfish poisoning (PSP) in Korea, and PSP is detected more in a wider area. However, the association between toxic dinoflagellates and shellfish poisoning is unclear. Therefore, it is necessary to understand the toxicity, detoxification, and compositional differences in PSP in Mytilus edulis exposed to PSP caused by A. catenella and A. pacificum. High-performance liquid chromatography with post-column oxidation was used to analyze PSP toxicity in poisoned M. edulis. PSP in M. edulis increased as the A. catenella and A. pacificum cell density increased. However, the cell density of A. catenella peaked faster than that of A. pacificum, and a high level of toxicity was detected. In the detoxification experiment, PSP in M. edulis decreased rapidly within 24 h in filtered seawater. However, PSP was continuously detected without decreasing below the detection limit until the last day of the experiment. In addition, the carbamate composition (GTX1+4) was detected as the main toxic composition in poisoned M. edulis, unlike in vegetative cells. GTX1+4 can poison shellfish quickly when toxic dinoflagellates appear in the marine environment. However, poisoned shellfish take a long time to be completely detoxified. Moreover, if shellfish continuously feed on poisonous dinoflagellates, their toxicity can increase rapidly due to biotransformation. Our results can help identify the mechanisms of shellfish toxicity and detoxification after PSP caused by toxic dinoflagellates.