Studies On The Source Apportionment And Damage Mechanism Of Paralytic Shellfish Toxins In Mytilus Galloprovincialis From The Bohai Sea

Paralytic Shellfish Toxins（PSTs）are neurotoxins mainly produced by marine dinoflagellates,which could not only reduce the physiological activity of marine organisms or even cause a large number of deaths,but also accumulate in marine shellfish and other economic animals,resulting in consumer poisoning.It has became a food safety risk factor that the international community focuses on.In recent years,the poisoning incidents caused by PSTs pollution in Mytilus galloprovincialis have occurred many times in Qinhuangdao area of Hebei Province,which seriously threatened the safety of consumers,endangered the development of shellfish industry and regional social stability,and caused great negative impact.Therefore,it has great scientific and practical significance to study the risk sources of PSTs in shellfish and explore the risk formation mechanism in bivalves in this area.In Order to explore the mechanism of PSTs in bivalves,an indoor exposure experiment was conducted to simulate the effects of red tide on M.galloprovincialis,an important economic shellfish in Qinhuangdao sea area.In order to analyze the accumulation and metabolism of paralytic shellfish toxins and the stress response of M.galloprovincialis.On this basis,through the detection and analysis of PSTs in Qinhuangdao and Tangshan coastal shellfish samples in two consecutive years,the source analysis of PSTs risk in Hebei coastal waters was realized.The main research contents and conclusions are as follows:（1）Liquid chromatography-tandem mass spectrometry（LC-MS/MS）was used to study the accumulation of PSTs in Hebei coastal economic shellfish in the Bohai Sea.The changes of PSTs pollution in shellfish from 2020 to 2021 were comprehensively analyzed,and the pollution law of PSTs in Bohai Sea was analyzed and explored.The results showed that the formation of PSTs was due to the accumulation of Alexandrium cysts,which led to the annual outbreak of Alexandrium.The highest content of PSTs in shellfish was in spring,which was the season of high occurrence of Alexandrium,followed by summer.The accumulation ability of PSTs in M.galloprovincialis was the highest among the different shellfish.Among them,the highest content of PSTs detected in 2020 is 10.5 times higher than the EU limit,which is a serious threat.（2）Alexandrium catenella（GY-H25 strain）was exposed to M.galloprovincialis which was the cause of PSTs poisoning in Qinhuangdao,and the accumulation and transformation of PSTs in M.galloprovincialis were studied.The results showed that SOD and pod had significant effects on PSTs stress,and there was a positive regulatory relationship between them;GST and Ca^2+,Mg²⁺-ATPase did not show significant stress characteristics;The activity ofγ-GCS increased continuously and was negatively regulated by T-GSH;The stress response of ATP was the most significant,and the difference was obvious in the two different exposure concentration groups.PSTs caused pathological damage to the mucosal epithelium and branch lumen of mussels,and no repair phenomenon was found within 15 days after removal of the source of stress.（3）High-throughput sequencing technology was used to detect the expression of genes in M.galloprovincialis viscera,and KEGG enrichment analysis was used to study the effects of PSTs stress on the physiological processes of mussel.The results were as follows:The significantly enriched pathways could be divided into four types according to their main functions,oxidative stress-related oxidative phosphorylation pathway and glutathione metabolic pathway,which were related to antioxidation;Signal transduction related MAPK signaling pathway,VEGF signaling pathway and HIF-1 signaling pathway regulate cell growth and new cell generation;Arachidonic acid pathway and cytochrome P450 pathway are important pathway of PSTs metabolism;An energy supply pathway,a glycolytic pathway,and a TCA cycle pathway.（4）Liquid chromatography-tandem mass spectrometry（LC-MS/MS）was used to detect PSTs in shellfish samples from Qinhuangdao sea area,and the data changes in 2021 were monitored on the basis of the existing data in 2020.The PSTs pollution law in Bohai Sea was analyzed and explored.The results showed that the formation of PSTs in Qinhuangdao sea area was due to the deposition of Alexandrium.alga cysts to form cyst beds,which led to the annual outbreak of Alexandrium.alga.Spring is the outbreak season,so the content of PSTs in shellfish samples is the highest in spring,followed by summer.M.galloprovincialis was the least sensitive to STX toxin of PSTs toxin,and its accumulation was the highest in shellfish.In 2020,the highest content of PSTs was 10.5 times higher than the safety limit,which posed a serious threat.