Screening for lipophilic marine toxins and their potential producers in coastal waters of Weihai in autumn,2020

Lipophilic marine toxins(LMTs)produced by some microalgae in the sea could accumulate in shellfish and pose potential threats to the health of seafood consumers.Phytoplankton and shellfish samples were collected from coastal waters of Weihai in Shandong Peninsula,China in autumn,2020,and screened for lipophilic marine toxins and their potential producers using liquid chromatography-tandem mass spectrometry(LC-MS/MS)analysis and high throughput sequencing of partial DNA(V4 region of the 18S rRNA gene)extracted from phytoplankton.Pectenotoxin-2(PTX2),trace amounts of azaspiracid(AZA1 or AZA40),and 13-desmethyl spirolide C(13-DesMe-C)were detected in phytoplankton samples,while PTX2 and gymnodimine(GYM)were detected in shellfish samples.The toxin content in shellfish samples was much lower than the regulatory limit or values reported previously.Results suggest that lipophilic marine toxins should have low risk in coastal waters of Weihai in autumn.Based on the data of high throughput sequencing,the OTUs were assigned to 5 identified species of Alexandrium,including A.ostenfeldii capable of producing 13-DesMe-C and GYM.Two OTUs were found closely related to the toxic species in genus Dinophysis,but it is impossible to assign them to any identified species due to the low resolving power of the V4 region for Dinophysis.The OTUs could not be assigned to any identified species in the genus Azadinium,suggesting the existence of unidentified species in this region.

Transfer of Paralytic Shellfish Toxins via Marine Food Chains:A Simulated Experiment

Objective To study the transfer of paralytic shellfish toxins （PST） using four simulated marine food chains： dinoflagellate Alexandrium tamarense→Artemia Artemia salina→Mysid shrimp Neomysis awatschensis; A. tamarense→N. awatschensis; A. tamarense→A, salina→Perch Lateolabrax japonicus; and A. tamarense→L, japonicus. Methods The ingestion of A. tamarense, a producer of PST, by L. japonicus, N. awatschensis, and A. salina was first confirmed by microscopic observation of A. tamarense cells in the intestine samples of the three different organisms, and by the analysis of Chl.a levels in the samples. Toxin accumulation in L. japonicus and N. awatschensis directly from the feeding on A. tamarense or indirectly through the vector of A. salina was then studied, The toxicity of samples was measured using the AOAC mouse bioassay method, and the toxin content and profile of A. tamarense were analyzed by the HPLC method. Results Both A. salina and N. awatschensis could ingest A. tamarense cells. However, the ingestion capability of A. salina exceeded that of N. awatschensis. After the exposure to the culture of A. tamarense （2 000 cells·mL^-1） for 70 minutes, the content of Chl.a in A. salina and N. awatschensis reached 0.87 and 0.024 μg.mg^-1, respectively. Besides, A. tamarense cells existed in the intestines of L. japonicus, N. awatschensis and A. salina by microscopic observation. Therefore, the three organisms could ingest A. tamarense cells directly. A. salina could accumulate high content of PST, and the toxicity of A. salina in samples collected on days 1, 4, and 5 of the experiment was 2.18, 2.6, and 2.1 MU.g^-1, respectively. All extracts from the samples could lead to death of tested mice within 7 minutes, and the toxin content in anemia sample collected on the 1st day was estimated to be 1.65×10 ^5 μg STX equal/individual. Toxin accumulation in L japonicus and N. awatschensis directly from the feeding on A. tamarense or indirectly from the vector ofA. salina was also studied. The mice injected with extracts from L japonicus and N. awatschensis samples that accumulated PST either directly or indirectly showed PST intoxication symptoms, indicating that low levels of PST existed in these samples. Conclusion Paralytic shellfish toxins can be transferred to L. japonicus, N. awatschensis, and A. salina from A. tamarense directly or indirectly via the food chains.

Spatial variation of lipophilic marine algal toxins and its relationship with physicochemical parameters in spring in Laizhou Bay,China

Lipophilic marine algal toxins(LMATs)are produced by some toxigenic microalgae,which pose a serious threat to marine ecosystem and even human health.The occurrence and environmental control factors of LMATs in the surface seawater and phytoplankton in spring in Laizhou Bay in which Huanghe(Yellow)River estuary is included,in Shandong,East China were investigated.Okadaic acid(OA),pectenotoxin-2(PTX2),dinophysistoxin-1(DTX1),pectenotoxin-2 seco acid(PTX2 SA),DTX2,7-epi-PTX2 SA,PTX11,and 13-desmethyl spirolide C(SPX1)were detected from the surface seawater samples,and PTX2,7-epi-PTX2 SA,OA,DTX2,DTX1,PTX2 SA,and PTX11 were discovered in the phytoplankton samples showed a decreasing trend.The concentrations of∑LMATs in the seawater and phytoplankton ranged 2.03-74.38 ng/L on average of 13.72 ng/L and 0.98-479.27 pg/L on average of 50.20 pg/L,respectively.The joint influence of terrigenous input and internal circulation could promote the growth,toxin production,and toxin release of toxin-producing algae,leading to a higher content of LMATs in the bay nearby the Huanghe River estuary in both seawater and phytoplankton.The concentration of LMATs in spring was higher than that in summer,showing obvious seasonal variation.In addition,no significant correlation between most of the physiochemical parameters and LMAT contents in seawater was revealed by correlation analysis except for the positive correlation between DTX2 and chlorophyll a,OA and NH4-N.However,the increase of dissolved inorganic nitrogen content in seawater could enhance the production of OA,DTX1,and DTX2 in phytoplankton due probably to that the inorganic N input could benefit the growth and stimulate toxin production of toxin-producing algae.The result also proved that some PTX2 may be originated from Procentrum spp.and OA,DTXs and part of PTX2 may be originated from Dinophysis spp.

Increased diversity and environmental threat of harmful algal blooms in the Southern Yellow Sea,China

Harmful algal blooms(HABs)in the Southern Yellow Sea(SYS)have shown a trend of increasing diversity and detrimental ef fects.While the Bohai Sea,East China Sea,and South China Sea have experienced a high incidence of HABs since the 1980s,the Yellow Sea provides a relatively healthy ecological environment in which fewer HABs have been documented before the 21s t century.Yet largescale blooms of the green macroalga Ulva prolifera(so-called“green tides”)have occurred annually since 2007 in the Yellow Sea.Six people were poisoned and one person died in Lianyungang in 2008 due to ingestion of algal toxins.Moreover,the Yellow Sea experienced co-occurrence of harmful red tides,green tides,and golden tides in 2017.This combination of events,rare worldwide,indicates the potential for further deterioration of the marine environment in the Yellow Sea,which may be related to climate change,aquaculture,and other human activities.Using the SYS as an example,we collected data of the frequency and scale of HABs over the years,as well as that of marine algal toxins,and analyzed the trend in the diversity of HABs in the SYS,to explore the causes and impacts of HABs,as well as the interrelationships among dif ferent types of HABs,including harmful red tides,green tides,and golden tides.We also attempted to improve our understanding of HAB evolution under the influence of global climate change and intensified human activities.