Lipophilic shellfish toxins in Dinophysis caudata picked cells and in shellfish from the East China Sea

Chemistry and bioactivity of marine algal toxins and their geographic distribution in China

Marine algal toxins are usually produced by some toxic algae during toxic algal blooms which can be accumulated in marine organisms through food chains, leading to contamination of aquatic products. Consumption of the contaminated seafood often results in poisoning in human being. Although algal toxins are harmful for human health, their unique structures and broad spectrum of biological activities have attracted widespread attention of chemists and pharmacologists. Marine algal toxins are not only a reservoir of biological active compound discovery, but also powerful tools for exploring life science. This review first provides a comprehensive overview of the chemistry and biological activities of marine algal toxins, with the aim of providing references for biological active compound discovery. Additionally, typical shellfish poisoning incidents occurred in China in the past 15 years and the geographical distribution of the marine algal toxins in China Sea are discussed, for the purpose of enhancing public awareness of the possible dangers of algal toxins.

Nationwide seasonal monitoring of lipophilic marine algal toxins in shellfish and causative microalgae along the coasts of South Korea

In this study, lipophilic marine algal toxins (LMATs)-producing microalgae were identified at 23 sites along the coasts of Korea, and distribution characteristics of LMATs in phytoplankton and mussels were investigated. The causative microalgae, including Gonyaulux spinifera, Dinophysis acuminata, D. caudata, and D. fortii, were observed in the study area, with notably higher densities during the summer. Significant correlations were found between the densities of these microalgae and the water temperature. Seasonal distribution patterns of LMATs in phytoplankton closely matched those observed in mussels. Notably, LMAT concentrations in mussels from the Yellow Sea were relatively high. PTX2 was detected predominantly in phytoplankton, and homo-yessotoxin was found mainly in mussels. Overall, LMAT concentrations were elevated in the summer, raising concerns about biotoxin contamination in shellfish. These results provide important insights into the dynamics of unmanaged marine biotoxins in Korea and offer baseline data for future safety management policies and inflow surveillance.

Spatial distribution of lipophilic shellfish toxins in seawater and sediment in the Bohai Sea and the Yellow Sea, China

Lipophilic shellfish toxins (LSTs) are widely distributed in marine environments worldwide, potentially threatening marine ecosystem health and aquaculture safety. In this study, two large-scale cruises were conducted in the Bohai Sea and the Yellow Sea, China, in spring and summer 2023 to clarify the composition, concentration, and spatial distribution of LSTs in the water columns and sediments. Results showed that okadaic acid (OA), dinophysistoxin-1 (DTX1) and/or pectenotoxin-2 (PTX2) were detected in 249 seawater samples collected in spring and summer. The concentrations of ∑LSTs in seawater were ranging of ND (not detected) -13.86, 1.60-17.03, 2.73-17.39, and 1.26-30.21 pmol L-1 in the spring surface, intermediate, bottom water columns and summer surface water layers, respectively. The detection rates of LSTs in spring and summer seawater samples were 97% and 100%, respectively. The high concentrations of ∑LSTs were mainly distributed in the north Yellow Sea and the northeast Bohai Sea in spring, and in the northeast Yellow Sea, the waters around Laizhou Bay and Rongcheng Bay in summer. Similarly, only OA, DTX1 and PTX2 were detected in the surface sediments. Overall, the concentration of ∑LSTs in the surface sediments of the northern Yellow Sea was higher than that in other regions. In sediment cores, PTX2 was mainly detected in the upper sediment samples, whereas OA and DTX1 were detected in deeper sediments, and LSTs can persist in the sediments for a long time. Overall, OA, DTX1 and PTX2 were widely distributed in the water column and surface sediments in the Bohai Sea and the Yellow Sea, China. The results of this study contribute to the understanding of spatial distribution of LSTs in seawater and sediment environmental media and provide basic information for health risk assessment of phycotoxins.

Five Karenia species along the Chinese coast: With the description of a new species, Karenia hui sp. nov. (Kareniaceae, Dinophyta)

Dinoflagellates within the genus Karenia are well known for their potential to cause harmful algal blooms and induce detrimental ecological consequences. In this study, five Karenia species, Karenia longicanalis, Karenia papilionacea, Karenia mikimotoi, Karenia selliformis, and a new species, Karenia hui sp. nov., were isolated from Chinese coastal waters. The new species exhibits the typical characteristics of the genus Karenia, including a linear apical groove and butanoyl-oxyfucoxanthin as the major accessory pigment. It is distinguished from the other Karenia species by a wide-open sulcal intrusion onto the epicone, a conical epicone with an apical crest formed by the rim of the apical groove, and a hunchbacked hypocone. It is most closely related to Karenia cristata, with a genetic divergence of 3.16 % (22 bp out of 883 bp of LSU rDNA). Acute toxicity tests indicated that the five Karenia species from China are all toxic to marine medaka Oryzias melastigma. Karenia selliformis and K. hui were very toxic to O. melastigma, resulting in 100 % mortality within 4 h and 24 h, respectively. Further analysis by high-performance liquid chromatography revealed that four species, K. selliformis, K. longicanalis, K. papilionacea and K. mikimotoi were capable of producing Gymnodimine-A (GYM-A). The highest GYM-A content was in K. selliformis (strain HK-43), in which the value was 889 fg/cell. No GYM-A was detected in the new species K. hui, however and its toxin remains unknown. Below we provide a comprehensive report of the morphology, phylogeny, pigment composition, and toxicity profiles of Karenia species along the Chinese coast. These findings contribute new insights for monitoring of Karenia species, with important toxicological and ecological implications.

Using solid phase adsorption toxin tracking and extended local similarity analysis to monitor lipophilic shellfish toxins in a mussel culture ranch in the Yangtze River Estuary

Harmful algal blooms (HABs) and their associated phycotoxins are increasing globally, posing great threats to local coastal ecosystems and human health. Nutrients have been carried by the freshwater Yangtze River and have entered the estuary, which was reported to be a biodiversity-rich but HAB-frequent region. Here, in situ solid phase adsorption toxin tracking (SPATT) was used to monitor lipophilic shellfish toxins (LSTs) in seawaters, and extended local similarity analysis (eLSA) was conducted to trace the temporal and special regions of those LSTs in a one-year trail in a mussel culture ranch in the Yangtze River Estuary. Nine analogs of LSTs, including okadaic acid (OA), dinophysistoxin-1 (DTX1), yessotoxin (YTX), homoyessotoxin (homoYTX), 45-OH-homoYTX, pectenotoxin-2 (PTX2), 7-epi-PTX2 seco acid (7-epi-PTX2sa), gymnodimine (GYM) and azaspiracids-3 (AZA3), were detected in seawater (SPATT) or rope farmed mussels. The concentrations of OA + DTX1 and homoYTX in mussels were positively correlated with those in SPATT samplers (Pearson test, p < 0.05), indicating that SPATT (with resin HP20) would be a good monitoring tool and potential indicator for OA + DTX1 and homoYTX in mussel Mytilus coruscus. The eLSA results indicated that late summer and early autumn were the most phycotoxin-contaminated seasons in the Yangtze River Estuary. OA + DTX1, homoYTX, PTX2 and GYM were most likely driven by the local growing HAB species in spring and summer, while Yangtze River diluted water may impact the accumulation of HAB species, causing potential phycotoxin contamination in the Yangtze River Estuary in autumn and winter. Together, the results showed that the mussel harvesting season, late summer and early autumn, would be the season with the greatest phycotoxin risk and would be the most contaminated by local growing toxic algae. Routine monitoring sites should be set up close to the local seawaters.

Risk characteristics of shellfish toxins in Mytilus unguiculatus around the Zhoushan Islands, East China Sea

The Zhoushan Islands, are an important area for Mytilus unguiculatus aquaculture, and are threatened by potentially harmful algal blooms. However, a full understanding of the risks posed by their toxin residues is still lacking. M. unguiculatus samples were collected from the area between 2020 and 2021 and analyzed for their toxin profiles to assess the contamination status of shellfish toxins. The main toxins detected were the paralytic shellfish toxins (PSTs), gymnodimine (GYM), and domoic acid (DA). Nine PSTs components were detected, the dominant ones being C1, C2, and GTX5, with an overall detection rate of 85.7 %. The detection rate of DA was 55.05 %, and GYM was detected in all samples. The toxin levels in the samples were significantly lower than the European Union regulatory limits, but toxin contamination was generally universal.

Co-occurrence of pectenotoxins and Dinophysis miles in an Indonesian semi-enclosed bay

The study aims to unravel the variability of Dinophysis spp. and their alleged toxins in conjunction with environmental drivers in Ambon Bay. Phytoplankton samples, lipophilic toxins and physiochemical water properties were analysed during a 1.5-year period. Three Dinophysis species (D. miles, D. caudata, and D. acuminata) were found in plankton samples, of which D. miles was the most abundant and persistently occurring species. Pectenotoxin-2 (PTX2) and its secoacid (PTX2sa) were detected throughout, and PTX2sa levels strongly correlated with D. miles cell abundance. The toxin showed a positive correlation with temperature, which may suggest that D. miles cells contain rather constant PTX2sa during warmer months. Dissolved nitrate concentrations were found to play a major role in regulating cell abundances and toxin levels. This study adds adequate information regarding marine biotoxins and potentially toxic species for future Harmful Algal Bloom management in Ambon and Indonesia at large.

Occurrence, spatial distribution, and partitioning behavior of marine lipophilic phycotoxins in the Pearl River Estuary, South China

The occurrence, spatial distribution, and partitioning behavior of 17 marine lipophilic phycotoxins (MLPs) in surface and bottom seawater, particulate organic matter (POM), and surface sediment from the Pearl River Estuary (PRE) were investigated to understand current contamination and the potential risks to marine ecosystems in this region. Nine MLPs were detected, including azaspiracid1-3, gymnodimine, okadaic acid, dinophysistoxin 1-2, pectenotoxin2 (PTX2), and homoyessotoxin, with Σ₁₇MLP concentrations ranging 545-12,600 pg L^-1 and 619-8,800 pg L^-1 in surface and bottom seawater, respectively; 0-294 ng g^-1 and 0.307-300 ng g^-1 dry weight (dw) in surface and bottom POM, respectively; and 3.90-982 pg g^-1 dw in surface sediment. Lower Σ₁₇MLP levels in the seawater were found at the mouth of the PRE, and gradually increased with increasing distance offshore. According to the calculated partition coefficient, the affinity of MLPs for the aquatic environment components was as follows (from highest to lowest): POM > seawater > sediment. Overall, the distribution and migration of MLPs in the PRE may depend on partition coefficients, the organic carbon fraction, and environmental factors.

Spatiotemporal distribution characteristics of yessotoxins and pectenotoxins in phytoplankton and shellfish collected from the southern coast of South Korea

The distribution characteristics of lipophilic marine biotoxins (LMTs), such as yessotoxins (YTXs) and pectenotoxins (PTXs) in phytoplankton, mussels, and commercial seafood were determined for the southern coast of South Korea. Gonyaulax spinifera and Dinophysis acuminata, which are the causative microalgae of YTXs and PTXs, were recorded during summer. Homo-YTX and PTX-2 were predominantly detected in phytoplankton (max: 5.7 μg g^-1 ww), whereas only YTXs were detected in mussels (max: 1.1 μg g^-1 ww). LMT concentrations in mussels were positively correlated with those in phytoplankton. However, there was a 1-month time gap in maximum LMT concentrations between mussels and phytoplankton. Homo-YTX was detected in commercial seafood, including red scallop and comb pen shell. However, homo-YTX concentrations in shellfish were below the recommended value of the European Food Safety Authority (3.75 mg YTX equivalents kg^-1); thus, the consumption of this seafood was not considered to be a significant risk for human health.

Prevalence and distribution of domoic acid and cyclic imines in bivalve mollusks from Beibu Gulf, China

Beibu Gulf is an important shellfish aquaculture area in the northwest of the South China Sea, China. In this study, the toxin profile and spatial-temporal distribution of domoic acid (DA) and 10 lipophilic phycotoxins were systematically analyzed in the bivalve mollusks collected in Beibu Gulf from October 2018 to October 2020. Neurotoxin DA was first detected in the mollusks from the investigative regions with a prevalence of 17.7%, peaking at 401 µg kg^-1. Cyclic imines (CIs) including gymnodimine-A (GYM-A, 46.6%) and 13-desmethyl-spirolide-C (SPX1, 15.8%) predominated the lipophilic phycotoxins in shellfish, peaking at 10.1 µg kg^-1 and 19.6 µg kg^-1, respectively. Gymnodimine-A partially accompanied by SPX1 was detected in all batches of shellfish samples, suggesting that Alexandrium ostenfeldii and Karenia selliformis were possible sources of CIs-group toxins in Beibu Gulf. During the investigative period, relatively higher levels of DA occurred in shellfishes from March to August, while slightly higher contents of CIs in mollusks appeared in October and December. Spatial distribution of the targeted phycotoxins demonstrated that shellfishes tended to accumulate relatively higher contents of toxins in Lianzhou, Qinzhou and Tieshan bays.

Progress on the investigation and monitoring of marine phycotoxins in China

Marine phycotoxins associated with paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), amnesic shellfish poisoning (ASP), neurotoxic shellfish poisoning (NSP), ciguatera fish poisoning (CFP), tetrodotoxin (TTX), palytoxin (PLTX) and neurotoxin β-N-methylamino-L-alanine (BMAA) have been investigated and routinely monitored along the coast of China. The mouse bioassay for monitoring of marine toxins has been progressively replaced by the enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC-MS/MS), which led to the discovery of many new hydrophilic and lipophilic marine toxins. PSP toxins have been detected in the whole of coastal waters of China, where they are the most serious marine toxins. PSP events in the Northern Yellow Sea, the Bohai Sea and the East China Sea are a cause of severe public health concern. Okadaic acid (OA) and dinophysistoxin-1 (DTX1), which are major toxin components associated with DSP, were mainly found in coastal waters of Zhejiang and Fujian provinces, and other lipophilic toxins, such as pectenotoxins, yessotoxins, azaspiracids, cyclic imines, and dinophysistoxin-2(DTX2) were detected in bivalves, seawater, sediment, as well as phytoplankton. CFP events mainly occurred in the South China Sea, while TTX events mainly occurred in Jiangsu, Zhejiang and Fujian provinces. Microalgae that produce PLTX and BMAA were found in the phytoplankton community along the coastal waters of China.

Emerging harmful algal bloom species over the last four decades in China

The first recorded micro-algae bloom in Chinese coastal waters dates back to 1933 and was caused by a mixture of Noctiluca scintillans and Skeletonema costatum sensu lato along the Zhejiang coast (the East China Sea). While well-documented harmful algal blooms (HABs) appeared to be extremely scarce from the 1950s to 1990, both the frequency and intensity have been reportedly increasing since 1990. Among them, the fish-killing HABs, mainly caused by Karenia mikimotoi, Karlodinium digitatum, Karlodinium veneficum, Margalefidinium polykrikoides, and Heterocapsa spp., have intensified. Karenia mikimotoi was responsible for at least two extremely serious events in the Pearl River Estuary in 1998 and the Taiwan Strait (in the East China Sea) in 2012, which appeared to be associated with abnormal climate conditions and excessive nutrients loading. Other major toxic algal blooms have been caused by the species responsible for paralytic shellfish poisoning (including Alexandrium catenella, Alexandrium pacificum, Gymnodinium catenatum) and diarrhetic shellfish poisoning (including Dinophysis spp., and a couple of benthic dinoflagellates). Consequent closures of shellfish farms have resulted in enormous economic losses, while consumption of contaminated shellfish has led to occasional human mortality in the Bohai Sea and the East China Sea. Expansions of these HABs species along the coastline of China have occurred over the last four decades and, due to the projected global changes in the climate and marine environments and other anthropological activities, there is potential for the emergence of new types of HABs in China in the future. This literature review aimed to present an updated overview of HABs species over the last four decades in China.

Chemodiversity of Brevetoxins and Other Potentially Toxic Metabolites Produced by Karenia spp. and Their Metabolic Products in Marine Organisms

In recent decades, more than 130 potentially toxic metabolites originating from dinoflagellate species belonging to the genus Karenia or metabolized by marine organisms have been described. These metabolites include the well-known and large group of brevetoxins (BTXs), responsible for foodborne neurotoxic shellfish poisoning (NSP) and airborne respiratory symptoms in humans. Karenia spp. also produce brevenal, brevisamide and metabolites belonging to the hemi-brevetoxin, brevisin, tamulamide, gymnocin, gymnodimine, brevisulcenal and brevisulcatic acid groups. In this review, we summarize the available knowledge in the literature since 1977 on these various identified metabolites, whether they are produced directly by the producer organisms or biotransformed in marine organisms. Their structures and physicochemical properties are presented and discussed. Among future avenues of research, we highlight the need for more toxin occurrence data with analytical techniques, which can specifically determine the analogs present in samples. New metabolites have yet to be fully described, especially the groups of metabolites discovered in the last two decades (e.g tamulamides). Lastly, this work clarifies the different nomenclatures used in the literature and should help to harmonize practices in the future.

Spatial distribution and source of biotoxins in phytoplankton from the South China Sea, China

Marine phycotoxins severely threaten ecosystem health and mariculture. This study investigates the spatial distribution and source of diverse phycotoxins in the South China Sea (SCS), during four 2019/2020 cruises. Saxitoxin (STX) and okadaic acid (OA) -groups, azaspiracids, cyclic imines, pectenotoxins (PTX), yessotoxins, and domoic acid (DA) toxins were analyzed in microalgal samples. PTX2 occurred with the highest (93.5%) detection rate (DR) during all cruises, especially in the Pearl River Estuary (PRE) in June 2019. Homo-yessotoxin (hYTX) and DA were found during three cruises in August 2020, and high DR of hYTX (67.7%, 29.3%) and DA (29.0%, 29.3%) in the PRE and Guangdong coast, respectively, in June 2019 and 2020, peaking at concentrations of 777 pg hYTX L^-1 and 38514 pg DA L^-1. The phycotoxin distribution demonstrated that DA-producing microalgae gathered close to the PRE and Guangdong coast, while hYTX-producing microalgae distributed relatively far offshore. Microalgae producing PTX2- and STX-group toxins were more widely living in the SCS. High-throughput sequencing results suggested that Alexandrium pacificum and Gonyaulax spinifera were responsible for STX-group toxins and hYTX, respectively, while Pseudo-nitzschia cuspidata was the main source of DA. Widely distributed PTX2, hYTX, and DA were reported for the first time in the SCS.

Occurrence and Trophodynamics of Marine Lipophilic Phycotoxins in a Subtropical Marine Food Web

Marine lipophilic phycotoxins (MLPs) are produced by toxigenic microalgae and cause foodborne illnesses. However, there is little information on the trophic transfer potential of MLPs in marine food webs. In this study, various food web components including 17 species of mollusks, crustaceans, and fishes were collected for an analysis of 17 representative MLPs, including azaspiracids (AZAs), brevetoxins (BTXs), gymnodimine (GYM), spirolides (SPXs), okadaic acid (OA), dinophysistoxins (DTXs), pectenotoxins (PTXs), yessotoxins (YTXs), and ciguatoxins (CTXs). Among the 17 target MLPs, 12, namely, AZAs1-3, BTX3, GYM, SPX1, OA, DTXs1-2, PTX2, YTX, and the YTX derivative homoYTX, were detected, and the total MLP concentrations ranged from 0.316 to 20.3 ng g^-1 wet weight (ww). The mean total MLP concentrations generally decreased as follows: mollusks (8.54 ng g^-1, ww) > crustaceans (1.38 ng g^-1, ww) > fishes (0.914 ng g^-1, ww). OA, DTXs, and YTXs were the predominant MLPs accumulated in the studied biota. Trophic dilution of the total MLPs was observed with a trophic magnification factor of 0.109. The studied MLPs might not pose health risks to residents who consume contaminated seafood; however, their potential risks to the ecosystem can be a cause for concern.

Monitoring Lipophilic Toxins in Seawater Using Dispersive Liquid-Liquid Microextraction and Liquid Chromatography with Triple Quadrupole Mass Spectrometry

The use of dispersive liquid–liquid microextraction (DLLME) is proposed for the preconcentration of thirteen lipophilic marine toxins in seawater samples. For this purpose, 0.5 mL of methanol and 440 µL of chloroform were injected into 12 mL of sample. The enriched organic phase, once evaporated and reconstituted in methanol, was analyzed by reversed-phase liquid chromatography with triple-quadrupole tandem mass spectrometry. A central composite design multivariate method was used to optimize the interrelated parameters affecting DLLME efficiency. The absence of any matrix effect in the samples allowed them to be quantified against aqueous standards. The optimized procedure was validated by recovery studies, which provided values in the 82–123% range. The detection limits varied between 0.2 and 5.7 ng L⁻¹, depending on the analyte, and the intraday precision values were in the 0.1–7.5% range in terms of relative standard deviation. Ten water samples taken from different points of the Mar Menor lagoon were analyzed and were found to be free of the studied toxins.

Evaluation of different strategies to minimize the matrix effects on LC-MS/MS analysis of multiple lipophilic shellfish toxins in both acidic and alkaline chromatographic conditions

Lipophilic shellfish toxins (LSTs) accumulated by shellfish pose a potential threat to consumer health. A mandatory routine monitoring of LSTs has been adopted for seafood products by liquid chromatography-mass spectrometry (LC-MS) in many countries. In this study, two methods developed on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) under acidic and alkaline chromatographic conditions were assessed for the determination of multiple LSTs. Different strategies including matrix solid-phase dispersion (MSPD), solid phase extraction (SPE) and sample dilution were applied and evaluated the matrix effects of mussel, scallop, clam, and oyster samples on the signal response of mass spectrometry. Results showed that the alkaline method achieved a lower limit of detection (LOD) and more robust compared to the acidic method. The obvious signal suppression of OA and DTX1 (55%-76%) and signal enhancement of PTX2 (27%-34%) occurred in the crude extracts of shellfish under acidic chromatography. In the alkaline method, no remarkable matrix effects of crude extracts were found except for the scallop matrix on the signal intensity of DTX1, AZA3 and GYM-A (121%-130%). Clean-up methods MSPD, SPE and sample dilution obviously reduced the inhibition of shellfish matrices on the signal response of OA and DTX1, however, which were still subject to signal inhibition under acidic condition. Sample dilution was more effective than SPE and MSPD in minimizing the matrix interference in both acidic and alkaline methods. Furthermore, sample dilution in combination with the alkaline chromatography was the most effective method. Bivalve mollusks harvested from Beibu Bay, South China Sea, were generally contaminated by GYM-A and SPX1 at low concentrations.

Occurrence and distribution of lipophilic phycotoxins in a subtropical bay of the South China Sea

Lipophilic phycotoxins (LPs) pose significant threats to the health of marine mammals, birds, and human beings. The distribution and components of lipophilic phycotoxins contamination in subtropical area in the South China Sea are rarely known. This study systematically assessed the composition, concentration, and distribution of typical LPs in a typical subtropical bay, Daya Bay located in the South China Sea. Phytoplankton, seawater, suspended particulate matter, sediments, and shellfish samples were simultaneously collected from Daya Bay, and analyzed using liquid chromatography with tandem mass spectrometry. Okadaic acid, dinophysistoxins-1, pectenotoxins-2, yessotoxin and its derivate homo-yessotoxin, azaspiracid-2, 13-desmethyl spirolide C and gymnodimine were widely spread in multiple media in Daya Bay. Pectenotoxins-2 was the most widely distributed and highly concentrated toxin in the marine environments of Daya Bay. Toxin homo-yessotoxin was only detected in sediments and shellfish samples, and none of yessotoxin group components were found in phytoplankton and seawater, indicating that sediments were the major source of yessotoxin in shellfish. The study strongly demonstrated the lipophilic phycotoxins accumulated in shellfish are multisource, not only derived from toxigenic algae, but also from other marine media containing lipophilic phycotoxins. This study systematically distinguished multi-pathways of bioaccumulation of LPs in the marine shellfish.

Fatty acid ester metabolites of gymnodimine in shellfish collected from China and in mussels (Mytilus galloprovincialis) exposed to Karenia selliformis

Marine shellfish exposed to the microalgae Karenia selliformis can accumulate gymnodimines (GYM). Shellfish samples collected from Beihai City in Guangxi Autonomous Region, and Ningde City in Fujian Province, in the South China Sea, as well as mussels Mytilus galloprovincialis fed on K. selliformis under laboratory conditions were analyzed. Gymnodimines and various fatty acid ester metabolites were detected in the clam Antigona lamellaris and pen shell Atrina pectinata, while no esters were found in the oyster Crassostrea sp. and the gastropod Batillaria zonalis despite positive detection of free GYM in both species. When present, the predominant acyl esters observed were 18:0-GYM-A and 20:1-GYM-A. Under laboratory conditions GYM-A was accumulated and metabolized to fatty acid esters in mussels exposed to K. selliformis, with 16:0-GYM-A and 20:1-GYM-A as the major variants. A novel compound with the same accurate mass as GYM-A and its 16:0 fatty acid ester were observed in the experimental mussels but was not present in the microalgal strain to which mussels were exposed. No significant differences of reactive oxygen species (ROS) levels and antioxidant enzymes were found between mussels fed on K. selliformis or GYM-free microalgae Isochrysis galbana. This suggests the accumulation of GYM and its metabolites does not significantly impact the physiological status of mussels. While it is currently not proven that GYM affects human health, risk assessments should consider the presence of GYM esters in naturally contaminated shellfish as part of exposure analysis.

Occurrence, distribution, source, and influencing factors of lipophilic marine algal toxins in Laizhou Bay, Bohai Sea, China

The composition, distribution, origin, and influencing factors of lipophilic marine algal toxins (LMATs) in surface seawater and phytoplankton in Laizhou Bay, China, were comprehensively investigated for the first time. Okadaic acid (OA), pectenotoxin-2 (PTX2), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), and pectenotoxin-2 seco acid (PTX2 SA) were discovered in surface seawater, whereas PTX2, OA, 7-epi-PTX-2 SA, DTX1, PTX2 SA, PTX11, and DTX2 were found in phytoplankton in a decreasing concentration order. ∑LMAT concentrations in seawater and phytoplankton were 1.08-35.66 ng/L (mean: 7.31 ng/L) and 0-3609.75 ng/L (mean: 191.38 ng/L), respectively. LMAT contents in seawater and phytoplankton exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner and outer bays. Dinophysis fortii, D. acuminata, D. rotundata, Procentrum lima, and P. minimum were identified as the potential origins of LMATs in Laizhou Bay. Moreover, increased nutrient level and decreased pH in seawater could increase LMAT content.

Sediment as a Potential Pool for Lipophilic Marine Phycotoxins with the Case Study of Daya Bay of China

Marine sediments can reserve many environmental pollutants. Lipophilic marine phycotoxins (LMPs) are natural toxic substances widespread in the marine environment; however, evidence of their existence in sediment is scarce. In the present study, in order to explore the occurrence and distribution characteristics of LMPs in sediment, surface sediment samples collected from a tropical area of Daya Bay (DYB) at different seasons, were analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). According to the results, up to six toxin compounds were detected in sediment samples from DYB, OA and DTX1 had the highest levels, followed by PTX2, homo-YTX, AZA2, and GYM. Although AZA2 and GYM were found in most of the sediment, OA, DTX1, homo-YTX, and PTX2 were the predominant toxin compounds, and PTX2 was the most ubiquitous toxin in sediment. The spatial distribution of LMP components in the sediment fluctuated with sampling times, partially according to the physical-chemical parameters of the sediment. There are likely several sources for LMPs existing in surface sediments, but it is difficult to determine contributions of a specific toxin-source in the sediment. Therefore, marine sediments may be a toxin reservoir for LMPs accumulation in benthic organisms via food chains.

Distribution Characteristics and Environmental Control Factors of Lipophilic Marine Algal Toxins in Changjiang Estuary and the Adjacent East China Sea

Marine algal toxins, highly toxic secondary metabolites, have significant influences on coastal ecosystem health and mariculture safety. The occurrence and environmental control factors of lipophilic marine algal toxins (LMATs) in the surface seawater of the Changjiang estuary (CJE) and the adjacent East China Sea (ECS) were investigated. Pectenotoxin-2 (PTX2), okadaic acid (OA), dinophysistoxin-1(DTX1), and gymnodimine (GYM) were detected in the CJE surface seawater in summer, with concentration ranges of not detected (ND)-105.54 ng/L, ND-13.24 ng/L, ND-5.48 ng/L, and ND-12.95 ng/L, respectively. DTX1 (ND-316.15 ng/L), OA (ND-16.13 ng/L), and PTX2 (ND-4.97 ng/L) were detected in the ECS during spring. LMATs formed a unique low-concentration band in the Changjiang diluted water (CJDW) coverage area in the typical large river estuary. PTX2, OA, and DTX1 in seawater were mainly derived from Dinophysis caudate and Dinophysis rotundata, while GYM was suspected to be from Karenia selliformis. Correlation analyses showed that LMAT levels in seawater were positively correlated with dissolved oxygen and salinity, but negatively correlated with temperature and nutrients, indicating that the hydrological condition and nutritional status of seawater and climatic factors exert significant effects on the distribution of LMATs.

Contamination status of lipophilic marine toxins in shellfish samples from the Bohai Sea, China

Lipophilic marine toxins in shellfish pose significant threats to the health of seafood consumers. To assess the contamination status of shellfish by lipophilic marine toxins in the Bohai Sea, nine species of shellfish periodically collected from five representative aquaculture zones throughout a year were analyzed with a method of liquid chromatography-tandem mass spectrometry (LC-MS/MS). Lipophilic marine toxins, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), yessotoxin (YTX), homo-yessotoxin (homo-YTX), azaspiracids (AZA2 and AZA3), gymnodimine (GYM), and 13-desmethyl spirolide C (13-DesMe-C), were detected in more than 95 percent of the shellfish samples. Toxins PTX2, YTX, 13-DesMe-C and GYM were predominant components detected in shellfish samples. Scallops, clams and mussels accumulated much higher level of lipophilic marine toxins compared to oysters. Toxin content in shellfish samples collected from different sampling locations showed site-specific seasonal variation patterns. High level of toxins was found during the stages from December to February and June to July in Hangu, while from March to April and August to September in Laishan. Some toxic algae, including Dinophysis acuminata, D. fortii, Prorocentrum lima, Gonyaulax spinifera and Lingulodinium polyedrum, were identified as potential origins of lipophilic marine toxins in the Bohai Sea. The results will offer a sound basis for monitoring marine toxins and protecting the health of seafood consumers.

Phycotoxins in scallops (Patinopecten yessoensis) in relation to source, composition and temporal variation of phytoplankton and cysts in North Yellow Sea, China

The North Yellow Sea is a major aquaculture production area for the scallop Patinopecten yessoensis. In this study, the temporal and spatial variation of phycotoxins in scallops, phytoplankton, and their cysts were analyzed during a survey conducted from June 2011 to April 2012 around Zhangzi Island. The study area is a semi-enclosed epicontinental sea surrounded by the Shandong Peninsula, the Liaodong Peninsula and the Korean Peninsula. The three main results of the study were as follows: (1) The saxitoxin-group toxins, okadaic acid and analogues, and pectenotoxins were the major phycotoxin residues found in scallops; (2) Six kinds of toxic microalgae were identified, Protoperidinium spp., Gonyaulax spp., and Alexandrium spp. were the dominant taxa; Seven types of potential marine toxin-producing dinoflagellates, A. tamarense, A. catenella, Dinophysis fortii, G. catenatum, Gambierdiscus toxicus, Azadinium poporum, and Pseudo-nitzschia pungen were identified as the primary source of phycotoxins and were present at relatively high density from June to October; and (3) azaspiracids and domoic acid might be new potential sources of toxin pollution. This study represents the first assessment to phycotoxins around Zhangzi Island in the North Yellow Sea.

Diel Variations in Cell Abundance and Trophic Transfer of Diarrheic Toxins during a Massive Dinophysis Bloom in Southern Brazil

Dinophysis spp. are a major source of diarrheic toxins to marine food webs, especially during blooms. This study documented the occurrence, in late May 2016, of a massive toxic bloom of the Dinophysis acuminata complex along the southern coast of Brazil, associated with an episode of marked salinity stratification. The study tracked the daily vertical distribution of Dinophysis spp. cells and their ciliate prey, Mesodinium cf. rubrum, and quantified the amount of lipophilic toxins present in seston and accumulated by various marine organisms in the food web. The abundance of the D. acuminata complex reached 43 &times; 10⁴ cells&middot;L^&minus;1 at 1.0 m depth at the peak of the bloom. Maximum cell densities of cryptophyceans and M. cf. rubrum (>500 &times; 10⁴ and 18 &times; 10⁴ cell&middot;L^&minus;1, respectively) were recorded on the first day of sampling, one week before the peak in abundance of the D. acuminata complex. The diarrheic toxin okadaic acid (OA) was the only toxin detected during the bloom, attaining unprecedented, high concentrations of up to 829 &micro;g&middot;L^&minus;1 in seston, and 143 ± 93 pg&middot;cell^&minus;1 in individually picked cells of the D. acuminata complex. Suspension-feeders such as the mussel, Perna perna, and barnacle, Megabalanus tintinnabulum, accumulated maximum OA levels (up to 578.4 and 21.9 &micro;g total OA&middot;Kg^&minus;1, respectively) during early bloom stages, whereas predators and detritivores such as Caprellidae amphipods (154.6 &micro;g&middot;Kg^&minus;1), Stramonita haemastoma gastropods (111.6 &micro;g&middot;Kg^&minus;1), Pilumnus spinosissimus crabs (33.4 &micro;g&middot;Kg^&minus;1) and a commercially important species of shrimp, Xiphopenaeus kroyeri (7.2 &micro;g&middot;Kg^&minus;1), only incorporated OA from mid- to late bloom stages. Conjugated forms of OA were dominant (>70%) in most organisms, except in blenny fish, Hypleurochilus fissicornis, and polychaetes, Pseudonereis palpata (up to 59.3 and 164.6 &micro;g total OA&middot;Kg^&minus;1, respectively), which contained mostly free-OA throughout the bloom. Although algal toxins are only regulated in bivalves during toxic blooms in most countries, including Brazil, this study indicates that human seafood consumers might be exposed to moderate toxin levels from a variety of other vectors during intense toxic outbreaks.

Interannual variability in Dinophysis spp. abundance and toxin accumulation in farmed mussels (Perna perna) in a subtropical estuary

This study evaluated an 8-year dataset (2007 to 2015, except 2008) in the attempt to identify the most susceptible periods for the occurrence of diarrheic shellfish poisoning (DSP) episodes associated with the presence of toxigenic dinoflagellates, Dinophysis spp., in the mussel farming area of Babitonga Bay (southern Brazil). Dinophysis acuminata complex was the most frequent (present in 66% of the samples) and abundant (max. 4100 cells L^-1) taxon, followed by D. caudata (14%; max. 640 cells L^-1) and D. tripos (0.9%; max. 50 cells L^-1). There was a marked onset of the annual rise in Dinophysis spp. abundance during weeks 21-25 (early winter) of each year, followed by a second peak on week 35 (spring). Mussel (Perna perna) samples usually started testing positive in DSP mouse bioassays (MBA) in late winter. Positive results were more frequent in 2007 and 2011 when the mean D. acuminata complex abundance was ~ 500 cells L^-1. Although positive DSP-MBA results were observed in only 11% of the samples during the studied period, the toxin okadaic acid (OA) was present in 90% of the analyzed mussels (max. 264 μg kg^-1). MBA results were positive when D. acuminata complex cell densities exceed 1200 ± 300 cells L^-1, while trace toxin amounts could be detected at cell densities as low as 150 ± 50 cells L^-1 (free OA) to 200 ± 100 cells L^-1 (conjugated OA). Low salinity and the meteorological conditions triggered by La Niña events were the main factors associated with both Dinophysis abundance and OA accumulation in mussels.

Mixtures of Lipophilic Phycotoxins: Exposure Data and Toxicological Assessment

Lipophilic phycotoxins are secondary metabolites produced by phytoplanktonic species. They accumulate in filter-feeding shellfish and can cause human intoxication. Regulatory limits have been set for individual toxins, and the toxicological features are well characterized for some of them. However, phycotoxin contamination is often a co-exposure phenomenon, and toxicological data regarding mixtures effects are very scarce. Moreover, the type and occurrence of phycotoxins can greatly vary from one region to another. This review aims at summarizing the knowledge on (i) multi-toxin occurrence by a comprehensive literature review and (ii) the toxicological assessment of mixture effects. A total of 79 publications was selected for co-exposure evaluation, and 44 of them were suitable for toxin ratio calculations. The main toxin mixtures featured okadaic acid in combination with pectenotoxin-2 or yessotoxin. Only a few toxicity studies dealing with co-exposure were published. In vivo studies did not report particular mixture effects, whereas in vitro studies showed synergistic or antagonistic effects. Based on the combinations that are the most reported, further investigations on mixture effects must be carried out.

Lipophilic marine toxins discovered in the Bohai Sea using high performance liquid chromatography coupled with tandem mass spectrometry

Some dinoflagellates can produce lipophilic marine toxins, which pose potent threats to seafood consumers. In the Bohai Sea, an important semi-closed inland sea with intensive mariculture industry in China, there is little knowledge concerning lipophilic marine toxins and their potential threats. In this study, net-concentrated phytoplankton samples were periodically collected from 5 typical mariculture zones around the Bohai Sea, including Laishan (LS), Laizhou (LZ), Hangu (HG), Qinhuangdao (QHD) and Huludao (HLD) in 2013 and 2014, and a method using high performance liquid chromatography (HPLC) coupled with a Q-Trap mass spectrometer was applied to analyze seven representative lipophilic marine toxins, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), yessotoxin (YTX), azaspiracid-1 (AZA1), gymnodimine (GYM), and 13-desmethyl spirolide C (desMeC). The method had high sensitivity and repeatability, and exhibited satisfactory recoveries for most of the lipophilic marine toxins (92.1-108%) except for AZA1 (65.8-68.9%). Nearly all the lipophilic marine toxins could be detected in phytoplankton samples from the Bohai Sea. OA, DTX1 and PTX2 were predominant components and present in most of the phytoplankton samples. The maximum content of lipophilic marine toxin in phytoplankton samples concentrated from seawater (OA 464 pg L^-1; DTX1 783 pg L^-1; YTX 86.6 pg L^-1; desMeC 15.6 pg L^-1; PTX2 1.11 × 10³ pg L^-1) appeared in June 2014. Based on toxins present in phytoplankton samples, it is implied that seafood in the Bohai Sea is more likely to be contaminated by OA group and PTX group toxins, and spring is the high-risk season for toxin contamination.

Occurrence of marine algal toxins in oyster and phytoplankton samples in Daya Bay, South China Sea

The occurrence and seasonal variations of marine algal toxins in phytoplankton and oyster samples in Daya Bay (DYB), South China Sea were investigated. Two Dinophysis species, namely, D. caudata and D. acuminata complex, were identified as Okadaic acid (OA)/pectenotoxin (PTX) related species. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis demonstrated that 2.04-14.47 pg PTX2 per cell was the predominant toxin in single-cell isolates of D. caudata. D. acuminata was not subjected to toxin analysis. The occurrence of OAs in phytoplankton concentrates of net-haul sample coincided with the presence of D. accuminata complex, suggesting that this species is most likely an OA producer in this sea area. OA, dinophysistoxins-1 (DTX1), PTX2, PTX2sa, gymnodimine (GYM), homoyessotoxin (homoYTX), and domoic acid (DA) demonstrated positive results in net haul samples. To our best knowledge, this paper is the first to report the detection of GYM, DA, and homoYTX in phytoplankton samples in Chinese coastal waters. Among the algal toxins, GYM demonstrated the highest frequency of positive detections in phytoplankton concentrates (13/17). Five compounds of algal toxins, including OA, DTX1, PTX2, PTX2sa, and GYM, were detected in oyster samples. DA and homoYTX were not detected in oysters despite of positive detections for both in the phytoplankton concentrates. However, neither the presence nor absence of DA in oysters can be determined because extraction conditions with 100% methanol used to isolate toxins from oysters (recommended by the EU-Harmonised Standard Operating Procedure, 2015) would likely be unsuitable for this water-soluble toxin. In addition, transformation of DA during the digestion process of oysters may also be involved in the negative detections of this toxin. GYM exhibited the highest frequency of positive results in oysters (14/17). OAs were only detected in the hydrolyzed oyster samples. The detection rates of PTX and PTX2sa in oysters were lower than those in the net haul samples.

Occurrence and Seasonal Variations of Lipophilic Marine Toxins in Commercial Clam Species along the Coast of Jiangsu, China

Recent studies have examined lipophilic marine toxins (LMTs) in shellfish and toxic algae worldwide, but the occurrence and seasonal variations of LMTs in commercial clams (including Mactra veneriformis, Ruditapes philippinarum, Meretrix meretrix, and Cyclina sinensis) at their major culturing area in Jiangsu, China, remain largely unexplored. In this study, a new solid phase extraction (SPE) in combination with an ultra-fast liquid chromatography and triple-quadrupole linear ion trap mass spectrometry (UFLC-TQ-MS) method was developed to determine the presence of 10 typical LMTs (okadaic acid (OA), yessotoxins (YTXs), azaspiracids (AZA1-3), pectenotoxins (PTX2), gymnodimine (GYM), dinophysistoxins (DTX1&2), and spirolides (SPX1)) in the aforementioned four clam matrices. After confirmation of its sensitivity and precision, this method was used to evaluate the amounts of LMTs in clam samples harvested in five aquaculture zones of the Jiangsu coastal area. Monthly variations of GYM, PTX2, OA, and DTX1&2 in 400 clam samples from the sample areas were determined from January 2014 through August 2015. Peak values were observed during May and August. This is the first systematic report of LMTs detected in clam samples harvested in Jiangsu. Follow-up research and the implementation of protective measures are needed to ensure the safety of clams harvested in this area.

Distribution of Marine Lipophilic Toxins in Shellfish Products Collected from the Chinese Market

To investigate the prevalence of lipophilic marine biotoxins in shellfish from the Chinese market, we used hydrophilic interaction liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure levels of okadaic acid (OA), azaspiracid (AZA1), pectenotoxin (PTX2), gymnodimine (GYM), and spirolide (SPX1). We collected and analyzed 291 shellfish samples from main production sites along a wide latitudinal transect along the Chinese coastline from December 2008 to December 2009. Results revealed a patchy distribution of the five toxins and highlighted the specific geographical distribution and seasonal and species variation of the putative toxigenic organisms. All five lipophilic marine biotoxins were found in shellfish samples. The highest concentrations of OA, AZA1, PTX2, GYM, and SPX1 were 37.3, 5.90, 16.4, 14.4, and 8.97 μg/kg, respectively. These values were much lower than the legislation limits for lipophilic shellfish toxins. However, the value might be significantly underestimated for the limited detection toxins. Also, these toxins were found in most coastal areas of China and were present in almost all seasons of the year. Thus, these five toxins represent a potential threat to human health. Consequently, studies should be conducted and measures should be taken to ensure the safety of the harvested product.