Distribution Characteristics Of Fat-soluble Algal Toxins In Different Environmental Media In Huanghuahai

Marine lipophilic algae toxins(MLATs)are a class of toxic organic metabolites produced by marine microalgae,and they are easily transferred and accumulated through food chain.It can not only influence on the marine ecosystem,marine fisheries and aquaculture industry,but also threat on human health.According to the literatures,a variety of MLATs are widely distributed in the near coastal marine environment around the world.The Yellow Sea and the Bohai Sea of China are important economic animal spawning and nursery field,and there are many aquaculture fields along their coast.In recent years,Chinese scholars have found MLATs from a number of typical aquaculture fields in the Yellow Sea,but there are still lack of systematic investigation and study on the distribution characteristics of MLATs in different marine environmental media of the Yellow Sea and the Bohai Sea.In this study,the Yellow Sea,the Bohai Sea,Haizhou Bay: a typical bay of the Yellow Sea,and the surrounding area of Dragon Island of the Bohai Sea are selected as the study area.Seawater,suspended particulate matter(SPM)and sediment samples are collected by the marine field investigation.In the laboratory,MLATs dissolved in the seawater samples are enriched by solid phase extraction.The SPM and sediment samples are extracted by ultrasonic assisted extraction,accelerated solvent extraction,respectively.High performance liquid chromatographyelectrospray ionization multi-stage mass spectrometry(HPLC-ESI-MS/MS)is used to determine eight kinds of typical MLATs including OA,DTX1,YTX,PTX2,AZA1,AZA2,SPX,GYM,in the seawater,SPM and sediments.Finally,the distribution characteristics and sources of MLATs in the marine environment of the Yellow Sea and the Bohai Sea have been discussed based on the related literatures.The results are as follows.(1)A broad area investigation has been done for eight kinds of typical MLATs in the surface sea water,SPM and sediment samples in Bohai.The results show that two kinds of MLATs,PTX2 and OA,have been detected in the Bohai Sea.Of which,PTX2 is dominated with concentration range between 0.59 to 6.95 ng/L,and average concentration of 2.20 ng/L.Four types of toxins,PTX2,OA,AZA1 and AZA2 were detected from the SPM.Of which,PTX2 is the major one,with the highest concentration of 3.68 ng/L.PTX2 and OA are detected from the sediment samples,but the content is low.The distribution of MLATs in the Bohai Sea shows the higher concentration in near coastal water,lower concentration in infralittoral water,relatively high concentration in the surrounding water of northern Yantai,Long Island,southern Tangshan and Dragon Island,and near coastal water of Bohai Bay.(2)The types of MLATs in the sea water,SPM and sediment samples In Yellow Sea are similar with that in the Bohai Sea.But YTX is detected from one suspended particle sample in Yellow Sea,though its concentration is below the limit.OA is detected in the sediment samples in the Yellow Sea.PTX2 is the dominated one in the Yellow Sea,with the concentration between 0.49 to 14.14 ng/L,and the average concentration of 4.19 ng/L;compared with that in the Bohai Sea,this PTX2 concentration is significantly higher.Particularly,the higher concentration region is in the northern Yellow Sea.The distribution of MLATs demonstrates a trend of higher concentration in the near coastal water and lower concentration in the far shore in Yellow Sea.A relatively high concentration is observed in the north of Yellow Sea,Haizhou Bay and the Yangtze River Estuary.North Yellow Sea is an important shellfish farming area in China.The risk of MLATs pollution in this area is higher than that in other areas.It is necessary to strengthen the monitor to the environment of North Yellow Sea,and to the MLATs in the shellfish aquafarm.(3)The distribution of MLATs in the large area investigation in the Haizhou Bay in March and October of 2016 shows that five types of MLATs,OA,PTX2,DTX1,GYM,and AZA2,are detected from coastal area.Of which,OA is the dominated one,with concentration range between 1.26 to 4.22 ng/L and 1.81 to 55.85 ng/L,average concentration of 2.39 ng/L and 26.81 ng/L in the March and October of 2016,respectively.In March,the GYM detected in Haizhou Bay is the first time to be discovered in China Seas,and GYM is discovered in a broad area in Haizhou |Bay in |October.OA,DTX1 and GYM are detected from the SPM,but their concentrations are below the limits.In the sediment survey of the Haizhou Bay in May of 2016,the results show that though OA,DTX1 and PTX2 are detected,however,their concentrations are low.Of which,the concentrations of the DTX1 is ranked the highest,OA the second,and PTX2 the third.Overall,the concentrations of MLATs in various environmental samples in Haizhou Bay in October are significantly higher than that in March of the same year.From April to September of 2016,the typical MLATs in the six sites of sea water,SPM and sediment samples in the red tides monitoring area of the Haizhou Bay have been monitored.OA,DTX1,PTX2 and GYM are detected from surface water.Of which,OA has the highest concentrations,with the average concentration of 23.19ng/L.In May,OA concentration in the surface seawater is far above concentrations in other months in a year.The highest OA concentration reachs 133.9 ng/L.The concentrations of the MLATs in SPM and sediment samples are much lower than that in seawater.From April 2016 to March 2017,the concentrations of MLATs in the two sites of sea water and SPM are monitored for one year(1 time per month)at the Lian Island of the Haizhou Bay.The concentrations of the MLATs in the sea water reach the highest value in a year,in September in the East of the Lian Island and in May in the West of the Lian Island,respectively.A small peak appears in Septemberin the West of the Lian Island.Based on the above results,the key seasons to monitor MLATs in the marine environment in the Haizhou bay should be in May,September and October.