Composition, Distribution Of Phycotoxins And Contamination Status Of Shellfish In Two Representative Agriculture Zones Of Shellfish In China

Phycotoxins are mainly produced by toxic dinoflagellates and diatoms, whichcan be accumulated to a high level in shellfish and transformed to human-beings viafood chain, and lead to poisoning incidents and even death. The northern Yellow Seais an important area for mariculture industry, and scallop Patinopecten yessoensis isone of the major species cultivated in this region, the production of P. yessoensis inthe northern Yellow Sea accounts for more than eighty percent of total production inChina. Sea area adjacent to the Changjiang River estuary is the most prominant areafor coastal eutrophication and harmuful algal blooms in China, and an importantmaricculture zone for mussels as well. These two regions are representative shellfishculture zones in China, and the contamination status of phycotoxins in shellfish raisedmuch concerns. In this study, numbers of phytoplankton samples and shellfishsamples including P. yessoensis and Mytilus coruscus were collected from the twoareas, all samples were analyzed for paralytic shellfish toxins (PSTs) byhigh-performance liquid chromatography with fluorescence detection (HPLC-FLD)and lipophilic shellfish toxins (LSTs) by liquid chromatography-tandem massspectrometry (LC–MS/MS).In the northern Yellow Sea, PSTs in phytoplankton samples, collected in July andAugust of2011, May and August of2012, were dominated by low potencyN-sulfocarbamoyl toxins C1,2, and lipophilic toxins including OA, DTX1, PTX2, andYTX were also detected in the phytoplankton samples. In the samples of scallop P.yessoensis, collected in July and August of2011, PST content was the highest inviscera tissue (2.34-9.48nmol/g), which was dominated by the N-sulfocarbamoyltoxins (C1,2and GTX5), followed by medium amount of carbamate toxins. PSTsprofiles in gonad and adductor muscle were similar to that in viscera. In the mantle, however, high-potency carbamate toxins occupied a large proportion of PSTs, themost predominate toxins were GTX2,3, STX and neoSTX (average84%), with littleN-sulfocarbamoyl toxins. Younger scallops have a much higher proportion ofN-sulfocarbamoyl toxins in the viscera, which closely resembled the toxin profiles ofnet-concentration phytoplankton samples. In addition, we also detected four lipophilicphycotoxins, i.e., OA, DTX1, PTX2, and YTX, were also detected in scallop samples.As far as we know, PTX2toxin was detected in P. yessoensis from this region for thefirst time. Among the four tissues, YTX was the most predominant component(average content2670μg/kg), which could account for more than ninety percent ofthe overall toxin content. Lipophilic toxin content in the vicera was the highest, andexceeded the EU food safety standard in some samples. In the phytoplankton samples,Alexandrium spp. and Dinophysis spp.(including D. acuminate and D. fortii) wereidentified, which were the potential sources of phycotoxins. Studies in the northernYellow Sea suggested that PST and LST contamination status in shellfish of thenorthern Yellow Sea was serious, and the exposure risk to phycotoxins was high.Spring and summer (May to September) are the high-risk seasons for phycotoxincontamination, and monitoring efforts on Alexandrium spp. and Dinophysis sppshould be emphasized in the two seasons. PSTs and LSTs in scallops P. yessoensisalso should be strenghened.The dominant PSTs profile in phytoplankton samples collected from the end ofMarch to the end of May in2011were dominated by the low-potencyN-sulfocarbamoyl toxins C1,2, whichaccounted for ninety-four percent of the totaltoxins, and LSTs components included OA, DTX1, PTX2, and YTX. In M.coruscus collected from April of2010to April of2012every week, PST content wasvery low Carbamate toxins (GTX1-4, STX, neoSTX) were major components,occupied eighty percent of total PSTs content, and proportion of N-sulfocarbamoyltoxins was quite low (less than fifteen percent). Five lipophilic toxins were detected inM. coruscus, and toxin level was relatively high in spring and summer. GYM wasdetected in M. coruscus collected from Shengsi mariculture area, OA, DTX1, PTX2,YTX, and GYM were detected in M. coruscus collected from Putuo Dongji seaculture area. GYM toxin was perennial in Zhoushan area. Meanwhile, the potentialphycotoxin-producing species, including A. tamarense/A. catenella, D. acuminate, D.fortii and D. caudata, were observed in phytoplankton samples. Sutdies in the sea areaadjacent to the Changjiang River estuary suggested that contamination status by PSTsin mussels was relatively low, but the contamination by LSTs was much serious.Spring and summer (from April to August) were high-risk seasons and the monitoringefforts on potential toxin-producing algae D. acuminate, D. fortii and D. caudateshould be performed. At the same time, mussel M. coruscus could be selected as atarget organism to strengthen the monitoring efforts on LSTs.In this study, we compared the composition, content and distribution pattterns ofphycotoxins in phytoplankton samples, and the contamination characteristics ofshellfish samples, collected from the northern Yellow Sea and the sea area adjacent tothe Changjiang River estuary. The potential relationship between phycotoxins inphytoplankton and shellfish were discussed, and the exposure risk to phycotoxinswere preliminarily analyzed, which provided a scientific basis for the marineenvironment monitoring and sanitary examination of shellfish products.