Screening of lipophilic marine toxins in marine aquaculture environment using liquid chromatography-mass spectrometry

Spatiotemporal distribution of lipophilic shellfish toxins in plankton and shellfish in the offshore regions of Shandong province, China

Lipophilic shellfish toxins (LSTs) threaten the ecosystem health and seafood safety. To comprehensively investigate the spatiotemporal distribution of common LSTs in phytoplankton, zooplankton and economic shellfish, three cruises were conducted in five typical offshore aquaculture regions of Shandong province, China, including Haizhou Bay, Jiaozhou Bay, Sanggou Bay, Sishili Bay and Laizhou Bay, in spring (March-April), summer (July-August) and autumn (November-December). This study revealed significant variability in the composition and content of LSTs in phytoplankton samples collected from different regions. Pectenotoxin-2 (PTX2), dinophysistoxin-1 (DTX1) and okadaic acid (OA) were mainly detected in the ranges of not detected (nd)-5045 pmol g-1 dry weight (dw), nd-159 pmol g-1 dw, and nd-154 pmol g-1 dw, respectively. In zooplankton, DTX1 and OA were the predominant components of LSTs, with the highest levels of ∑LSTs in spring ranging from nd to 406 pmol g-1 dw. Spearman's correlation analysis between LSTs and environmental factors indicated significant correlations for the contents of homo-yessotoxin (hYTX), gymnodimine-A (GYM-A), and spirolide-1 (SPX1) with these factors. Totally relatively low levels of LSTs with dominative DTX1 were detected in economic shellfish, which showed a low risk to seafood safety for human health.

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.

Spatiotemporal variations of domoic acid: New findings in the sedimentary environment of a typical nearshore mariculture bay, China

Domoic acid (DA) is a neurotoxin produced by marine microalgae. It tends to accumulate in marine shellfish and fish, posing a threat to aquaculture and seafood consumers' health. In this study, DA in the surface and bottom seawater, sediment, and porewater of the Jiaozhou Bay, a typical mariculture bay in China, was systematically investigated for the first time over different seasons. Surprisingly, a high concentration of DA was discovered in the marine sediment porewater (maximum detected concentration: 289.49 ng/L) for the first time. DA was found to be extensively distributed in the water body and sedimentary environment of the Jiaozhou Bay. DA in the surface and bottom seawater of Jiaozhou Bay in spring was uniformly distributed, whereas DA showed obvious spatial variations in summer and winter. The high concentration areas of DA are located in the north of Jiaozhou Bay and decreased to the south areas. DA was also distributed in the sediment (spring mean: 316.57 ng/kg; summer mean: 10.22 ng/kg; winter mean: 237.08 ng/kg) and porewater (spring mean: 129.70 ng/L; summer mean: 53.54 ng/L; winter mean: 19.90 ng/L) of Jiaozhou Bay. The DA concentrations in the surface sediment and porewater were higher in the spring than in the winter and summer, contrary to the seasonal variation pattern observed in the surface and bottom seawater. The DA concentration in porewater was significantly higher than in the surface and bottom seawater, indicating that the risk of pollution contamination from DA to benthic fishery organisms may be underestimated. Overall, DA is widely distributed in the seawater and also in the benthic environment of Jiaozhou Bay and exhibited potential harm to fishery organisms varied greatly with seasons. It is an important discovery for marine algae toxins and has important guiding significance and important indicative role for the routine monitoring and management of DA pollution in water and benthic environment.

Marine toxins in seafood: Recent updates on sample pretreatment and determination techniques

Marine toxins can lead to varying degrees of human poisoning, often resulting in fatal symptoms and causing significant economic losses in seafood-producing regions. To gain a deeper comprehension of the role of marine toxins in seafood and their impact on the environment, it is imperative to develop rapid, cost-effective, environmentally friendly, and efficient methods for sample pretreatment and determination to mitigate adverse impacts of marine toxins. This review presents a comprehensive overview of advancements made in sample pretreatment and determination techniques for marine toxins since 2017. The advantages and disadvantages of various technologies were critically examined. Additionally, the current challenges and future development strategies for the analysis of marine toxins are provided.

Occurrence and distribution of phycotoxins in the Antarctic Ocean

Lipophilic phycotoxins (LPTs) and domoic acid (DA) in Antarctic seawater, as well as parts of the South Pacific and the Southern Indian Oceans were systematically investigated. DA and six LPTs, namely pectenotoxin-2 (PTX2), okadaic acid (OA), yessotoxin (YTX), homo-yessotoxin (h-YTX), 13-desmethyl spirolide C (SPX1), and gymnodimine (GYM), were detected. PTX2, as the dominant LPTs, was widely distributed in seawater surrounding Antarctica, whereas OA, YTX, and h-YTX were irregularly distributed across the region. The total concentration of LPTs in surface seawater ranged from 0.10 to 13.57 ng/L (mean = 2.20 ng/L). ∑LPT levels were relatively higher in the eastern sea areas of Antarctica than in the western sea areas. PTX2 was the main LPT in the vertical profiles, and the PTX2 concentration was significantly higher in the epipelagic zone than water depths below 200 m. The predominant sources of PTX2 and OA in Antarctic sea areas are likely to be Dinophysis.

Non-targeted LC-MS/MS metabolomic profiling of human plasma uncovers a novel Mediterranean diet biomarker panel

INTRODUCTION

Consumption of a Mediterranean diet (MD) has established health benefits, and the identification of novel biomarkers could enable objective monitoring of dietary pattern adherence.

OBJECTIVES

The present investigation performed untargeted metabolomics on blood plasma from a controlled study of MD adherence, to identify novel blood-based metabolite biomarkers associated with the MD pattern, and to build a logistic regression model that could be used to characterise MD adherence.

METHODS

A hundred and thirty-five plasma samples from n = 58 patients collected at different time points were available. Using a 14-point scale MD Score (MDS) subjects were divided into 'high' or 'low' MDS adherence groups and liquid chromatography-mass spectrometry (LC-MS/MS) was applied for analysis.

RESULTS

The strongest association with MDS was pectenotoxin 2 seco acid (r = 0.53; ROC = 0.78), a non-toxic marine xenobiotic metabolite. Several lipids were useful biomarkers including eicosapentaenoic acid, the structurally related lysophospholipid (20:5(5Z,8Z,11Z,14Z,17Z)/0:0), a phosphatidylcholine (P-18:1(9Z)/16:0) and also xi-8-hydroxyhexadecanedioic acid. Two metabolites negatively correlated with MDS, these were the monoacylglycerides (0:0/16:1(9Z)/0:0) and (0:0/20:3(5Z,8Z,11Z)/0:0). By stepwise elimination we selected a panel of 3 highly discriminatory metabolites and developed a linear regression model which identified 'high MDS' individuals with high sensitivity and specificity [AUC (95% CI) 0.83 (0.76-0.97)].

CONCLUSION

Our study highlights the utility of metabolomics as an approach for developing novel panels of dietary biomarkers. Quantitative profiling of these metabolites is required to validate their utility for evaluating dietary adherence.

Monthly distribution of lipophilic marine biotoxins and associated microalgae in the South Sea Coast of Korea throughout 2021

Aquaculture farms have been established along the South Sea Coast of Korea, supplying most of the seafood consumed domestically. However, annual harmful algal blooms pose a potential threat to seafood safety. This study aimed to determine the spatial and seasonal distributions of 12 lipophilic marine biotoxins (LMTs) in phytoplankton and mussels in the region in 2021. Solid-phase adsorption toxin tracking (SPATT) was used to monitor the cumulative compositions of LMTs in seawater. LMT concentrations were also determined in twelve commercially available species of domestic shellfish to evaluate the potential risks to human health. Gonyaulux spinifera and Dinophysis acuminata, causative microalgae of yessotoxins (YTXs) and pectenotoxins (PTXs), respectively, showed high densities in the region from May to July. This period corresponded to high LMT concentrations in phytoplankton and mussels. Phytoplankton mainly contained PTX-2 and homo-YTX, with a maximum concentration of 2300 ng g-1 wet weight (ww) in May. In contrast, mussels mainly contained homo-YTX and YTX, with a maximum concentration of 1300 ng g-1 ww in July. LMTs-producing microalgae showed low densities and concentrations after July, whereas mussels accumulated toxins until September. In the SPATT sampler, more diverse LMTs were detected than in seawater, phytoplankton, and mussels. For example, dinophysistoxin-1 and azaspiracid-2 were detected only in SPATT. YTXs were detected in domestic seafood samples, including mussels, red scallops, and pen shells, but the concentrations were below the European Food Safety Agency recommended standard of 3.75 mg YTX-eq. kg-1. Moreover, the hazard quotient was less than 100 in all scenarios, indicating that the human health risk was not significant. This study provides valuable data on monthly distribution patterns of LMTs in the South Sea Coast of Korea and can serve as baseline data for future management policies of marine biotoxins.

Occurrence and phase distribution of lipophilic marine algal toxins in the bottom boundary layer and sediment-porewater system of two mariculture sites

To date, understanding the fate of lipophilic marine algal toxins (LMATs) in benthic environments on which cultivated shellfish depend is still limited. In this work, the occurrence, concentration levels, and phase distributions of LMATs in the benthic environments of two mariculture sites (Sishili and Rongcheng Bays) in China were investigated for the first time. Five LMATs: okadaic acid (OA), pectenotoxin-2 (PTX2), gymnodimine, 13-desmethyl spirolide C, and azaspiracid-2 (AZA2) and three derivatives: dinophysistoxin-1 isomer (DTX1-iso), pectenotoxin-2 seco acid, and 7-epi- pectenotoxin-2 seco acid were detected in different environmental samples. OA and PTX2 were the dominant LMATs in the bottom boundary layer (BBL) and sediment, whereas AZA2 was present in the sediment only. Notably, DTX1-iso was found for the first time to be widely distributed in the benthic environments of the bays. In BBL, the average proportion of LMATs in the dissolved phase (99.20%) was much higher than in the particulate phase (0.80%). Partition of LMATs was more balanced between sediment porewater (57.80% average proportion) and sediment (42.20%). The concentrations of ∑LMATs in the BBL seawater ranged from 19.09 ng/L to 41.57 ng/L (mean of 32.67 ng/L), and the spatial distribution trend was higher in offshore than nearshore. ∑LMATs concentrations in the sediment and porewater of the two bays ranged from 17.04 ng/kg to 150.13 ng/kg (mean of 53.58 ng/kg) and from 8.29 ng/L to 120.58 ng/L (mean of 46.63 ng/L), respectively. Their spatial distributions differed from those in BBL, showing a trend of high concentrations in areas with heavy land-based inputs. ∑LMATs concentrations in porewater were significantly higher than those in BBL seawaters, suggesting that the potential hazards of LMATs to benthic organisms may be underestimated.

Sample pooling and incurred samples improve analytical throughput and quality control of lipophilic phycotoxins screening in bivalve mollusks

Lipophilic marine biotoxins (LMBs) are one of the main risks associated with the consumption of mussels and oysters. Sanitary and analytical control programs are developed to detect the occurrence of these toxins in seafood before they reach toxic levels. To ensure quick results, methods must be easy and fast to perform. In this work, we demonstrated that incurred samples were a viable alternative to validation and internal quality control studies for the analysis of LMBs in bivalve mollusks. These samples were used to optimize, validate, and monitor a simple and fast ultrasound-assisted extraction (UAE) procedure. An internal quality control material containing okadaic acid (227 ± 46 µg kg-1) was produced and characterized. This material had its homogeneity and stability verified and was included as a quality control in all batches of analytical routine. Besides, a sample pooling protocol for extracts analysis was developed, based on tests for COVID-19. Up to 10 samples could be analyzed simultaneously, reducing the instrumental time of analysis by up to 80%. The UAE and sample pooling approaches were then applied to more than 450 samples, of which at least 100 were positive for the okadaic acid group of toxins.

Prevalence of the neurotoxin domoic acid in the aquatic environments of the Bohai and Northern Yellow seas in China

Domoic acid (DA), a natural marine phytotoxin produced by toxigenic algae, is harmful to fishery organisms and the health of seafood consumers. In this study, we performed a whole-sea area investigation of DA in seawater, suspended particulate matter (SPM), and phytoplankton of the Bohai and Northern Yellow seas to clarify the occurrence, phase partitioning, spatial distribution, potential sources, and environmental influencing factors of DA in the aquatic environment. DA in different environmental media was identified using liquid chromatography-high resolution mass spectrometry and liquid chromatography-tandem mass spectrometry. DA was found to be predominantly in a dissolved phase (99.84 %) in seawater with only 0.16 % in SPM. Dissolved DA (dDA) was widely detected in nearshore and offshore areas of the Bohai Sea, Northern Yellow Sea, and Laizhou Bay with concentrations ranging from < limits of detection (LOD) to 25.21 ng/L (mean: 7.74 ng/L), < LOD to 34.90 ng/L (mean: 16.91 ng/L), and 1.74 ng/L to 38.20 ng/L (mean: 21.28 ng/L), respectively. dDA levels were relatively lower in the northern part than in the southern part of the study area. In particular, the dDA levels in the nearshore areas of Laizhou Bay were significantly higher than in other sea areas. This may be due to seawater temperature and nutrient levels exerting a crucial impact on the distribution of DA-producing marine algae in Laizhou Bay during early spring. Pseudo-nitzschia pungens may be the main source of DA in the study areas. Overall, DA was prevalent in the Bohai and Northern Yellow seas, especially in the nearshore aquaculture zone. Routine monitoring of DA in the mariculture zones of the northern seas and bays of China should be performed to warn shellfish farmers and prevent contamination.

Occurrence and distribution of lipophilic marine algal toxins in the coastal seawater of Southeast China and the South China Sea

The composition, levels, and spatial distribution of dissolved lipophilic marine algal toxins (LMATs) including cyclic imines (CIs), yessotoxins (YTXs), okadaic acid (OA) and its derivatives, pectenotoxins (PTXs), azaspiracids (AZAs), and brevetoxins (BTXs) in the coastal waters of Southeast China (Xiamen) and the South China Sea (Hainan Island and Beibu Gulf) were investigated and compared for the first time. Dissolved AZA3 was firstly detected in the coastal seawater of China. OA and PTX2 were widely distributed in the three areas studied. Gymnodimine (GYM), 13-desmethyl spirolide C (SPX1), YTX, and homo-yessotoxins (h-YTX) were found mainly in the South China Sea. The average ∑LMAT concentrations in the coastal waters of Xiamen, Hainan Island, and Beibu Gulf were 10.02 ng/L, 4.21 ng/L, and 44.27 ng/L, respectively. More groups and much higher concentrations of LMATs occurred in the South China Sea than that in the other sea areas of China.

Contribution of Mass Spectrometry to the Advances in Risk Characterization of Marine Biotoxins: Towards the Characterization of Metabolites Implied in Human Intoxications

A significant spread and prevalence of algal toxins and, in particular, marine biotoxins have been observed worldwide over the last decades. Marine biotoxins are natural contaminants produced during harmful algal blooms being accumulated in seafood, thus representing a threat to human health. Significant progress has been made in the last few years in the development of analytical methods able to evaluate and characterize the different toxic analogs involved in the contamination, Liquid Chromatography coupled to different detection modes, including Mass Spectrometry, the method of choice due to its potential for separation, identification, quantitation and even confirmation of the different above-mentioned analogs. Despite this, the risk characterization in humans is still limited, due to several reasons, including the lack of reference materials or even the limited access to biological samples from humans intoxicated during these toxic events and episodes, which hampered the advances in the evaluation of the metabolites responsible for the toxicity in humans. Mass Spectrometry has been proven to be a very powerful tool for confirmation, and in fact, it is playing an important role in the characterization of the new biotoxins analogs. The toxin metabolization in humans is still uncertain in most cases and needs further research in which the implementation of Mass Spectrometric methods is critical. This review is focused on compiling the most relevant information available regarding the metabolization of several marine biotoxins groups, which were identified using Mass Spectrometry after the in vitro exposition of these toxins to liver microsomes and hepatocytes. Information about the presence of metabolites in human samples, such as human urine after intoxication, which could also be used as potential biomarkers for diagnostic purposes, is also presented.

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.

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.

Variability and profiles of lipophilic marine toxins in shellfish from southeastern China in 2017-2020

A total of 1338 samples were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to study the toxin profiles of lipophilic marine toxins in bivalve mollusks collected from the southeast coast of China from 2017 to 2020. The most abundant toxin was HomoYTX, followed progressively by YTX and PTX2. Low proportions of OA, DTX-1, and DTX-2 were found. No AZA1, AZA2, and AZA3 were quantified above limit of quantitation (LOQ). The highest concentrations of HomoYTX, YTX, PTX2, OA, DTX-1, and DTX-2 were 429, 98.0, 40.3, 33.0, 22.6, and 26.5 μg/kg, respectively. Mussels (Mytilus galloprovincialis, Perna viridis), scallop (Chlamys farreri) and clam (Atrina pectinate) accumulated higher toxin levels than clams (Sinonovaculla Constricta, Ruditapes philippinarum), oyster (Crassostrea gigas) and scallop (Arca granosa). Homo YTX and PTX2 levels reached the maximum in July and June, respectively, and the OA-group peaked in August. The results provide a reliable basis for monitoring marine toxins and protecting the health of aquatic consumers.

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.

Employ of arbuscular mycorrhizal fungi for pharmaceuticals ibuprofen and diclofenac removal in mesocosm-scale constructed wetlands

This study investigated the effects of arbuscular mycorrhizal fungi (AMF) colonization on the growth of wetland plants (Glyceria maxima), and treatment performance in constructed wetlands (CWs) under the stress of pharmaceuticals ibuprofen (IBU) and diclofenac (DCF). Results showed that the growth of G. maxima was significantly increased by AMF colonization. AMF significantly increased the activities of antioxidant enzymes (peroxidase and superoxide dismutase) and soluble protein content in wetland plants, but the contents of malondialdehyde and O₂^•- were reduced. The removal efficiencies of TOC, PO₄^3--P, NH₄⁺-N, and TN were increased in AMF+ treatments by 6%, 11%, 15% and 11%, respectively. AMF increased the removal efficiencies of IBU and DCF by 6-14% and 2-21%, respectively, and reduced the content of their metabolites (2-OH IBU, CA IBU and 4'-OH DCF) in the effluent. Besides, the presence of AMF increased the contents of IBU and DCF in plant roots, while decreased their transportation to shoots. AMF symbiosis decreased the contents of IBU metabolites (2-OH IBU and CA IBU) but increased the contents of DCF metabolite (4'-OH DCF) in the roots of the host plant. In conclusion, these results indicated that AMF plays a promising role in CWs for emerging pollutants removal.

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.

Simple determination of six groups of lipophilic marine algal toxins in seawater by automated on-line solid phase extraction coupled to liquid chromatography-tandem mass spectrometry

Lipophilic marine algal toxins (LMATs) are highly toxic secondary metabolites produced by marine microalgae that pose a great threat to marine aquaculture organisms and human health. In this study, a novel and automated method for the simultaneous determination of six groups of LMATs in seawater was developed by on-line solid phase extraction (SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Condition optimization and method validation were performed, and the recoveries of all 14 target LMATs featuring different properties ranged from 83.5% to 96.0%. The limits of detection of most target compounds were within ≤3.000 ng/L with good precision (relative standard deviation ≤ 12.1%) and linearity (R²≥0.9916). Compared with off-line SPE methods, the proposed on-line SPE method has better recovery, sensitivity, repeatability, and throughput; in addition, the volume of seawater sample necessary to conduct determinations is greatly reduced in the present method. Finally, the method was applied to determine LMATs in actual seawater samples collected from the Bohai and South Yellow Seas of China in summer, and okadaic acid and pectenotoxin-2 were detected in all seawater samples. The highest concentration of ∑LMATs (22.23 ng/L) occurred in the coastal mariculture area of Shandong Province. Therefore, routine monitoring of LMATs in seawater of the coastal mariculture zone is necessary to prevent shellfish contamination especially in summer, and the proposed on-line SPE-LC-MS/MS method is a powerful way for direct and automatic detection of various LMATs in coastal mariculture area.

Distribution characteristics of lipophilic marine phycotoxins in the sediment: A case study in Jiaozhou Bay, China

Marine sediments serve as a sink for environmental pollutants, such as lipophilic marine phycotoxins (LMPs). To reveal the fate of LMPs, we studied their distribution characteristics in sediments. From January 2016 to August 2017, we sampled surface sediments from Jiaozhou Bay (JZB) of the North Yellow Sea, and their solid-phase extracts were analyzed using liquid chromatography-tandem mass spectrometry. Three LMPs viz. okadaic acid (OA), dinophysistoxin-1 (DTX1), and pectentoxin-2 (PTX2) were predominant in the sediments. Also, PTX2 distribution was more extensive in the area, while OA and DTX1 were more concentrated. Having the same toxigenic algae origin, the spatial distribution of OA, DTX1, and PTX2 in the sediments was similar.

Aqueous photodegradation of okadaic acid and dinophysistoxin-1: Persistence, kinetics, photoproducts, pathways, and toxicity evaluation

Diarrhetic shellfish poisoning (DSP) toxins are a class of natural organic contaminants that pose a serious threat not only to marine ecosystems and fisheries but also to human health. They are widely distributed in coastal and offshore waters around the world. However, the persistence and photochemical degradation characteristics of DSP in an aqueous environment are still unclear. This study aimed to elucidate the photochemical fate of two representative DSP toxins, namely, okadaic acid (OA) and dinophysistoxin-1 (DTX1). Results showed that photo-mediated chemical reactions play a crucial role in eliminating DSP toxins in seawater. However, the degradation of OA and DTX1 was relatively slow under natural solar radiation, with a removal efficiency of 90.0% after exposure for more than 20 days. When the reaction solutions of OA and DTX1 were exposed to Hg lamp radiation, their degradation followed pseudo-first-order kinetics, and was remarkably influenced by seawater pH and metal-ion concentration. A total of 24 tentative transformation products (TPs) of OA and DTX1 were identified via liquid chromatography high-resolution mass spectrometry. C12 (C₄₃H₆₆O₁₁) and C24 (C₄₄H₆₈O₁₁) were the main TPs. The following possible photodegradation pathways were proposed: decarboxylation, photoinduced hydrolysis, chain scission, and photo-oxidation. Toxicity assays via protein phosphatase 2A inhibition proved that photochemical processes could significantly reduce the DSP toxicity of irradiated solutions by approximately 88%. This work provides an enhanced understanding of the fate of DSP toxins in the aqueous environment, allowing for an improved assessment of their environmental impacts.

First determination of extracellular paralytic shellfish poisoning toxins in the culture medium of toxigenic dinoflagellates by HILIC-HRMS

Paralytic shellfish poisoning (PSP) toxins have received considerable attention in recent years because of their adverse effects on marine breeding industries and human health. In this study, a reliable method for the analysis of extracellular PSP toxins in the culture medium of marine toxic dinoflagellates was developed for the first time using graphitized carbon black-solid-phase extraction and hydrophilic interaction liquid chromatography-high-resolution mass spectrometry. The limit of quantification of typical PSP toxins in algal culture medium ranged from 0.072 μg/L to 0.151 μg/L under optimal conditions. Satisfactory absolute recoveries (87.5%-102.4%), precision (relative standard deviation ≤ 7.6%), and linearity (R² ≥ 0.9998) were also achieved. In addition, the proposed method was applied to screen and determine the extracellular PSP toxins of two typical toxigenic dinoflagellates, Alexandrium minutum and Alexandrium tamarense. The total concentrations of the extracellular PSP toxins in A. minutum and A. tamarense over the whole growth period were within 2.0-735.5 and 2.0-19.2 μg/L, respectively. The concentrations of extracellular PSP toxins varied remarkably in the different growth stages of A. minutum and A. tamarense, and the contents of some extracellular PSP toxins were substantially higher than those of intracellular PSP toxins. Therefore, the extracellular PSP toxins released by toxigenic red tide algae cannot be ignored, and their environmental fate, bioavailability, and potential harm to aquatic environment need to be investigated in future studies.

Nontarget Screening and Toxicity Evaluation of Diol Esters of Okadaic Acid and Dinophysistoxins Reveal Intraspecies Difference of Prorocentrum lima

High-resolution mass spectrometry (HRMS) analysis with the assistance of molecular networking was used to investigate intracellular toxin profiles of five Prorocentrum lima (P. lima) strains sampled from the north Yellow Sea and South China Sea. Mice were used as a model species for testing the acute toxicity of intracellular okadaic acid (OA) and dinophysistoxins (DTXs) in free and esterified states. Results showed that OA and DTX1 esterified derivatives were detected in all P. lima samples, accounting for 55%-96% of total toxins in five strains. A total of 24 esters and 1 stereoisomer of DTX1 (35S DTX1) were identified based on molecular networking and MS data analysis, 15 esters of which have been reported first. All P. lima strains displayed specific toxin profiles, and preliminary analysis suggested that toxin profiles of the five P. lima strains might be region-related. Moreover, acute toxicity in mice suggested higher toxicity of esters compared with free toxins, which highlights the importance and urgency of attention to esterified toxins in P. lima.

Magnetic nanostructures for marine and freshwater toxins removal

Marine and freshwater toxins contaminate water resources, shellfish and aquaculture products, causing a broad range of toxic effects in humans and animals. Different core-shell nanoparticles were tested as a new sorbent for removing marine and freshwater toxins from liquid media. Water solutions were contaminated with 20 μg/L of marine toxins and up to 50 μg/L of freshwater toxins and subsequently treated with 250 or 125 mg/L of nanoparticles. Under these conditions, carbon nanoparticles removed around 70% of saxitoxins, spirolides, and azaspiracids, and up to 38% of diarrheic shellfish poisoning toxins. In the case of freshwater toxins, the 85% of microcystin LR was eliminated; other cyclic peptide toxins were also removed in a high percentage. Marine toxins were adsorbed in the first 5 min of contact, while for freshwater toxins it was necessary 60 min to reach the maximum adsorption. Toxins were recovered by extraction from nanoparticles with different solvents. Gymnodinium catenatum, Prorocentrum lima, and Microcystis aeruginosa cultures were employed to test the ability of nanoparticles to adsorb toxins in a real environment, and the same efficacy to remove toxins was observed in these conditions. These results suggest the possibility of using the nanotechnology in the treatment of contaminated water or in chemical analysis applications.

Monitoring and warning of lipophilic marine algal toxins in mariculture zone based on toxin profiles of phytoplankton

Some toxigenic dinoflagellates can produce lipophilic marine algal toxins (LMATs), which are potent threats to marine breeding industries. In this study, a new method based on the profiling analysis of six LMAT classes in phytoplankton was developed for the monitoring and warning of LMATs in mariculture zones. This method was applied to monitor and evaluate LMATs in the Jiaozhou Bay and the Changjiang estuary in China. Results demonstrated that the occurrence and spatiotemporal variations of LMATs in mariculture zones can be revealed by the toxin profiles of phytoplankton, indicating the method's effectiveness for the comprehensive monitoring of the composition and levels of various LMATs in coastal aquaculture zones. The method was further used as an alarm for potential pollution risk from LMATs in mariculture zones at an early stage. The "alert" thresholds of LMAT pollution in the mariculture zones were preliminarily proposed based on the statistical data analysis of LMATs in phytoplankton in three typical mariculture areas in China. This study is the first to conduct simultaneous monitoring and warning of multi-class LMATs based on toxin profiles of phytoplankton, thereby providing new insight into the monitoring and early warning of natural poisonous pollutants in coastal aquaculture zones around the world.

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.

Accumulation and esterification of diarrhetic shellfish toxins from the aqueous phase in laboratory-exposed mussels

In recent years, marine bivalves cultured in the natural environment have been confirmed to accumulate diarrhetic shellfish toxins (DSTs) from the aqueous phase. To investigate the effects of varying seston concentrations on DST accumulation, mussels (Mytilus galloprovincialis) were exposed to comparable concentrations of okadaic acid (OA) and dinophysistoxin-1 (DTX1) in 0.45-μm filtered seawater spiked with varying concentrations of ambient suspended particles at 0, 10, 30, 60, 90, and 120 mg L^-1, for 96 h. Effects of seston additions on the mussels' feeding on nontoxic microalgae, Isochrysis galbana, the stability of dissolved toxins and the anatomical compartmentalization of toxins were also assessed. Results showed that mussels more readily accumulated OA than DTX1 from the aqueous phase. Three potential mechanisms of the effects of seston on toxin accumulation were identified. First, seston at low concentrations (10 mg L^-1) adsorbed toxins and thus promoted toxin accumulation. Second, seston enhanced the degradation of aqueous OA and DTX1, and possibly reduced the adsorption by digestive gland (DG) cells through simple diffusion due to competitive adsorption. Third, the clearance rate of mussels was significantly reduced at high seston concentrations (120 mg L^-1). The esterification of DSTs was maximized in DG tissue, although a high percentage (52%) of DSTs was distributed in non-visceral tissues of mussels exposed to aqueous toxins. This study suggests that the risk of benthic DST-producing microalgae to marine cultured shellfish should be taken into consideration, even in the absence of a bloom of toxic microalgae in the water column.

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.

Distribution, partitioning, and seasonal variation of lipophilic marine algal toxins in aquatic environments of a typical semi-closed mariculture bay

Lipophilic marine algal toxins (LMATs) pose a potential threat to the health of marine shellfish consumers and marine breeding industries. In this study, LMATs in dissolved phases (DP) and particulate phases (PP) in the seawater of Jiaozhou Bay were accurately determined over four seasons to understand their composition, level, phase partitioning, spatiotemporal variation, and potential sources in aquatic environments of a typical semi-closed mariculture bay. Various LMATs, such as okadaic acid (OA), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), gymnodimine (GYM), 13-desmethyl spirolide C (SPX1), pectenotoxin-2 (PTX2), pectenotoxin-2 seco acid (PTX2 SA), and pectenotoxin-11 (PTX11), were detected in DP and PP; of these, OA and PTX2 were the dominant LMATs in DP and PP, respectively. The average proportion of ΣLMATs in DP (97.5%) was significantly higher than that in PP (2.5%), which indicates that LMATs are predominantly partitioned into DP. The total concentrations of LMATs in DP ranged from 4.16 ng/L to 23.19 ng/L (mean, 13.35 ng/L) over four seasons. The highest levels of LMATs in DP and PP were found in summer (mean, 16.71 ng/L) and spring, respectively, while the maximum variety of LMATs was found in autumn. This result suggests that seasonal changes could influence the composition, concentration, and phase partitioning of LMATs in aquatic environments of a coastal semi-closed mariculture bay. ΣLMAT concentrations were higher in the western region than in the eastern region of the bay, where shellfish may have a greater risk of exposure. Dinophysis acuminata, Dinophysis fortii, and Prorocentrum minimum were the potential sources of LMATs in the aquaculture seawater. Overall, various LMATs occurred in the semi-closed mariculture bay, and the persistence and bioavailability of these toxins in aquaculture seawater should be determined in future research.

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.

Influence of draw solution type and properties on the performance of forward osmosis process: Energy consumption and sustainable water reuse

Single and multi-component fertilizers were used as a draw solution (DS) in forward osmosis (FO) to produce high-quality water from synthetic and seawater solution, eliminating the need for DS regeneration and reducing the operational energy. The effect of DS type, concentration, circulation flow rates on the FO water flux (WF), specific water flux (SWF), percentage water recovery (%W_recovery), reverse salt flux (RSF) and percentage salt rejection (%R) were studied. The results showed that single fertilizer draw solution (SFDSs) produced higher WF (4.43 L/m².h), %W_recovery (30%) and RSF (60%) in comparison with multi-component draw solution (MCDS) with WF, %W_recovery and RSF of 2.57 L/m².h, 17% and 46%, respectively. DS with higher concentration produced the highest SWF and %W_recovery and consumed less energy. MCDS with concentration of 200 g/L showed SWF in the range of 14.0 to 10.4 L/m²h and energy consumption of 0.312 kW/h m³ in comparison with 10 to 7.8 L/m²h and 0.23 kW/h m³ for MCDS with concentration of 100  g/L. Increasing the recirculation flow rate showed minimum effect on WF and up to 35% energy saving. Pure water extracted using liquid fertilizers utilizing the unique FO mass transport properties balanced nutrient requirement and the water quality parameters, thereby sustaining the aquaponics industry.

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.

Selective enrichment and quantification of okadaic acid in shellfish using an immunomagnetic-bead-based liquid chromatography with tandem mass spectrometry assay

Okadaic acid is a marine biotoxin that primarily occurs in shellfish and can cause diarrheic shellfish poisoning in humans. When analyzing biological samples using liquid chromatography with tandem mass spectrometry, the presence of complex matrices is a major issue. Thus, it is crucial to selectively and simply extract the target analyte from samples and minimize matrix effects simultaneously. To meet this need, an immunomagnetic-bead-based liquid chromatography with tandem mass spectrometry method was developed to detect okadaic acid in shellfish. Magnetic beads bound to monoclonal antibody against okadaic acid were used as affinity probes to specifically enrich okadaic acid in samples, which effectively eliminated matrix effects. A magnetic separator was used to aggregate and separate magnetic particles from sample matrices, and methanol was used to elute okadaic acid from the magnetic beads. Standard solution prepared with methanol was employed directly for quantitative analysis. Several experimental conditions were optimized to improve performance. The method is of interest as a rapid (10 min) sample clean-up and selective enrichment tool, and it showed good linearity and sensitivity, with reported limits of detection and quantitation of 3 and 10 μg/kg, respectively. Fifty-three shellfish samples from an aquatic products market were tested using this method, and four samples positive for okadaic acid were found.

Rapid and direct mass spectrometric analysis of antibiotics in seawater samples

The SD-DSI is a simple, rapid, and sensitive method for both qualitative and quantitative analysis of antibiotics in seawater samples.

Effect of Suspended Particulate Matter on the Accumulation of Dissolved Diarrhetic Shellfish Toxins by Mussels (Mytilus galloprovincialis) under Laboratory Conditions

In recent years, detection of trace amounts of dissolved lipophilic phycotoxins in coastal waters has been possible using solid phase adsorption toxin tracking (SPATT) samplers. To explore the contribution of dissolved diarrhetic shellfish toxins (DST) to the accumulation of toxins by cultivated bivalves, mussels (Mytilus galloprovincialis) were exposed to different concentrations of purified okadaic acid (OA) and dinophysistoxin-1 (DTX1) in filtered (0.45 µm) seawater for 96 h. Accumulation and esterification of DST by mussels under different experimental conditions, including with and without the addition of the food microalga Isochrysis galbana, and with the addition of different size-fractions of suspended particulate matter (SPM) (<75 µm, 75–150 µm, 150–250 µm) were compared. Results showed that mussels accumulated similar amounts of OA and DTX1 from seawater with or without food microalgae present, and slightly lower amounts when SPM particles were added. Mussels preferentially accumulated OA over DTX1 in all treatments. The efficiency of the mussel’s accumulation of OA and DTX1 from seawater spiked with low concentrations of toxins was higher than that in seawater with high toxin levels. A large proportion of OA (86–94%) and DTX1 (65–82%) was esterified to DTX3 by mussels in all treatments. The proportion of I. galbana cells cleared by mussels was markedly inhibited by dissolved OA and DTX1 (OA 9.2 µg L⁻¹, DTX1 13.2 µg L⁻¹) in seawater. Distribution of total OA and DTX1 accumulated in the mussel tissues ranked in all treatments as follows: digestive gland > gills > mantle > residual tissues. However, the percentage of total DST in the digestive gland of mussels in filtered seawater (67%) was higher than with the addition of SPM particles (75–150 µm) (51%), whereas the gills showed the opposite trend in filtered seawater with (27%) and without (14.4%) SPM particles. Results presented here will improve our understanding of the mechanisms of DST accumulation by bivalves in marine aquaculture environments.

Occurrence and distribution of marine natural organic pollutants: Lipophilic marine algal toxins in the Yellow Sea and the Bohai Sea, China

For the first time, the composition, concentration and distribution characteristics of typical lipophilic marine algal toxins (LMATs) are investigated in surface seawater, suspended particulate matter (SPM) and sediments from the Yellow Sea and the Bohai Sea, China. Pectenotoxin-2 (PTX2) and okadaic acid (OA) were detected in offshore surface seawater samples (n=67) of the Yellow and Bohai Seas, and PTX2 was found in higher concentrations than OA. The concentrations of PTX2 were between 0.49 and 14.14ng/L. OA, dinophysistoxin-1(DTX1), PTX2 and gymnodimine (GYM) were detected in the nearshore surface seawater samples (n=20) of the Haizhou Bay of the Yellow Sea. OA concentrations were between 11.47 and 55.85ng/L. There was a large degree of variation in the concentrations of DTX1, from <limit of quantification (LOQ) up to 143.14ng/L. The nearshore surface seawater samples (n=13) obtained from the Longdao area of the Bohai Sea mainly contain OA (5.00-24.14ng/L) and DTX1 (1.52-49.39ng/L), with PTX2 concentrations being less than the LOQ. Several LMATs were also detected both in the SPM and sediment samples of each study area. In summary, the LMAT composition and concentration levels in the surface seawater found in nearshore samples were substantially different from those of samples from the distant shore, which indicated the obvious regional characteristics of LMATs according to their spatial distribution in the Yellow Sea and the Bohai Sea.

Profiling of Extracellular Toxins Associated with Diarrhetic Shellfish Poison in Prorocentrum lima Culture Medium by High-Performance Liquid Chromatography Coupled with Mass Spectrometry

Extracellular toxins released by marine toxigenic algae into the marine environment have attracted increasing attention in recent years. In this study, profiling, characterization and quantification of extracellular toxin compounds associated with diarrhetic shellfish poison (DSP) in the culture medium of toxin-producing dinoflagellates were performed using high-performance liquid chromatography–high-resolution mass spectrometry/tandem mass spectrometry for the first time. Results showed that solid-phase extraction can effectively enrich and clean the DSP compounds in the culture medium of Prorocentrum lima (P. lima), and the proposed method achieved satisfactory recoveries (94.80%–100.58%) and repeatability (relative standard deviation ≤9.27%). Commercial software associated with the accurate mass information of known DSP toxins and their derivatives was used to screen and identify DSP compounds. Nine extracellular DSP compounds were identified, of which seven toxins (including OA-D7b, OA-D9b, OA-D10a/b, and so on) were found in the culture medium of P. lima for the first time. The results of quantitative analysis showed that the contents of extracellular DSP compounds in P. lima culture medium were relatively high, and the types and contents of intracellular and extracellular toxins apparently varied in the different growth stages of P. lima. The concentrations of extracellular okadaic acid and dinophysistoxin-1 were within 19.9–34.0 and 15.2–27.9 μg/L, respectively. The total concentration of the DSP compounds was within the range of 57.70–79.63 μg/L. The results showed that the proposed method is an effective tool for profiling the extracellular DSP compounds in the culture medium of marine toxigenic algae.

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.