| The distribution of toxic and harmful algae in the ocean is getting more widespread as a result of human activities and climate change.Toxic and harmful algae can be found in coastal areas around the world,with incidents of shellfish pollution caused by lipophilic marine algal toxins(LMATs)occurring from time to time.China is a major country in marine aquaculture,with extensive distribution of nearshore aquaculture areas.In recent years,shellfish in nearshore aquaculture areas of China has also faced the threat of LMAT pollution.However,there is still a lack of in-depth understanding of the composition,concentration,and geographical distribution of LMATs in different environmental media in the nearshore and offshore aquatic environment of China.In this study,In September of 2021,different environmental media samples were collected from the Bohai Sea,the North Yellow Sea and the South Yellow Sea to the Yangtze River Estuary of the East China Sea,and sixty-five surface seawater samples,sixty-five bottom seawater samples,fifteen different layer seawater samples,sixty-five surface sediment samples,forty-nine sediment porewater samples and thirty-six phytoplankton samples were obtained.Ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS)was used to determine the concentration of fourteen typical LMATs in these samples.The composition,concentration,and spatial distribution characteristics of LMATs in the aquatic environment along the Bohai Sea to the Yangtze River estuary were discussed.The preliminary understanding is as follows:(1)There are mainly seven typical LMATs distributed in the surface seawater,bottom seawater,and different layers of seawater of the Bohai Sea,the Yellow Sea and Yangtze River estuary areas of the East China Sea,including YTX,PTX2,OA H-YTX,GYM,AZA1,and AZA2.All these seven LMATs are distributed in the surface seawater,and five LMATs are detected in the bottom seawater: OA,PTX2,GYM,YTX,and h-YTX.Only PTX2,OA,and h-YTX are detected in the seawater of different layers at the three stations in the Yellow Sea.OA and PTX2 are the two dominant LMATs with the highest proportion and widest distribution in surface and bottom seawaters.In terms of the concentration of LMATs in seawater,the concentration of LMATs in surface seawater is slightly higher than that in bottom seawater.Compared with the concentration levels of LMATs reported domestically and internationally,the concentration levels of LMATs in seawater of the studied areas are at lower levels.The concentration of LMATs in seawater from different sea areas varies greatly,with an overall trend of high concentration in nearshore waters and low concentration in offshore waters.The high concentration areas of LMATs in seawater are mainly distributed in the intersection area of Bohai Sea and Yellow Sea,and the North Yellow Sea area outside the Shandong Peninsula.(2)Six typical LMATs were detected in phytoplankton samples,including DTX1,PTX2,OA,h-YTX,YTX,and GYM.The detection rates of OA and PTX2 are both100%,with relatively high proportions(4.10%～88.90% and 20.10%～84.70%,respectively),making them the two dominant LMATs in phytoplankton.The concentration ranges of OA and PTX2 are 0.08 ng/L～1.42 ng/L and 0.09ng/L～6.74ng/L,respectively,with an average concentration of 1.07 ng/L and 2.07ng/L,respectively.The proportion of these two toxins in phytoplankton at different stations fluctuates greatly.In terms of average concentration of Σ LMATs in phytoplankton,the Yellow Sea>the Bohai Sea> near areas of the Yangtze River estuary in the East China Sea.In terms of spatial distribution,areas with high concentrations of LMATs in phytoplankton are mainly distributed in the North Yellow Sea,especially in the surrounding areas of the Shandong Peninsula.(3)Eight LMATs were detected in surface sediments,including YTX,PTX2,OA,h-YTX,GYM,DTX1,AZA2,and AZA1.The proportion of OA and PTX2 accounted for ΣLMATs ranges from10.6% to 96.1% and 28.6% to 92.3%,respectively.They are the two main LMATs in surface sediment and are widely distributed,which are consistent with the composition of OA and PTX2 in seawater.The concentration ranges of OA and PTX2 in surface sediment are 25.11 pg/g～1497.18 pg/g and 22.48pg/g～1032.95 pg/g,respectively,with average concentrations of 149.81 pg/g and184.81 pg/g,indicating significant fluctuations in concentration.The spatial distribution pattern of OA,PTX2 and ΣLMATs is basically consistent,and the high concentration area mainly located in the North Yellow Sea.(4)There are five LMATs in sediment porewater,such as YTX,PTX2,DTX2,OA,and h-YTX;of these,OA and PTX2 were the dominant LMATs in porewater,and were widely distributed in the studied areas.Concentrations of OA and PTX2 in porewater samples from different sea areas fluctuate significantly,ranging from 0.04ng/L to 4.25 ng/L and<LOQ to 4.26 ng/L,respectively.Except for OA and PTX2,the content of other LMATs is relatively low.The spatial distribution of OA,PTX2,andΣLMATs in porewater remains basically consistent,and the high value areas all located in the Yellow Sea.In summary,there are abundant LMATs species in the aquatic environment of the Bohai Sea,the North Yellow Sea,and along the sea areas from South Yellow Sea to the Yangtze River Estuary,including nine common LMATs: YTX,PTX2,OA,DTX1,DTX2,h-YTX,GYM,AZA1,and AZA2.Among them,OA and PTX2 are the two dominant LMATs with the highest concentration and the widest distribution in each studied sea area.Overall,the concentration of LMATs in the aquatic environment along the Bohai Sea to the Yangtze River estuary is at a relatively low level,but there are significant differences in the concentration levels of LMATs in each sea area.ΣLMAT concentration decreased in the following orders: Yellow Sea>Bohai Sea>Yangtze River estuary.The high concentration area of LMATs is mainly located in the North Yellow Sea,especially in the sea area around the Shandong Peninsula and the intersection area of Bohai and Yellow Sea. |
