C18 (up)-graphitized carbon (down) solid-phase extraction disks were used for the first time to simultaneously and rapidly enrich 35 dissolved marine algal toxins (MATs) from seawater, with a maximum difference in log Kow values of 12.3. The enriched MATs were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The flow rate of the pretreatment process was 100 mL/min, and a 2000-fold enrichment was achieved for seawater, with recoveries of the target MATs exceeding 65.9%. The developed method demonstrated high sensitivity and excellent precision, with limits of detection as low as 2.0 × 10-4 ng/L and average relative standard deviations ≤12.8%. Real seawater samples from Liaodong Bay and Beibu Bay were analyzed using this method to detect dissolved MATs. Nine MATs, including gymnodimine, pectenotoxin-2, okadaic acid (OA), 19-epi-OA, dinophysistoxin-1 (DTX1), 19-epi-DTX1, homo-yessotoxin, gonyautoxin-2 (GTX2), and GTX3, were detected in seawater samples from the selected research areas. Notably, 19-epi-OA and 19-epi-DTX1 were identified for the first time in China. The concentrations of dissolved ∑MATs in Liaodong Bay and Beibu Bay ranged from 26.12 to 56.95 ng/L and 28.12 to 51.98 ng/L, respectively. This study proposes a potential technique for exploring the distribution characteristics of multiple MATs across large-scale coastal seawater.

The environmental impact and resistance issues of antibiotics have drawn global concern. However, there is still a lack of in-depth understanding regarding antibiotic pollution in coastal bays at different latitudes in China. This work systematically explored the spatiotemporal distribution, potential sources, and ecological risks of antibiotics in seawater from coastal bays of China at different latitudes during different seasons. Twenty-one antibiotics were detected in seawater samples, primarily including quinolones, sulfonamides, tetracyclines, macrolides, and chloramphenicols. A widespread distribution of these antibiotics (>50 % detection rates) was detected in the coastal seawater of China. Florfenicol (FF) and tetracycline (TET) were the predominant antibiotics in the seawater from different latitude bays of China. The antibiotic levels were higher in autumn, with concentrations ranging from 4.40 ng/L to 22.17 ng/L (mean: 8.69 ng/L). Seawater from the northern bays had relatively higher antibiotic concentrations. The highest concentration of antibiotics was found in Jiaozhou Bay during the autumn, with levels ranging from 7.39 ng/L to 22.17 ng/L (13.88 ng/L). Aquaculture, livestock farming, and medical use were identified as primary sources. Ecological risks were generally low, except for moderate risk from ofloxacin (OFL) at station A5 in the autumn of Jiaozhou Bay.

The increasing entry of antibiotics into the marine environment has led to marine pollution and the potential global spread of antibiotic resistance genes, posing a threat to both marine ecosystems and human health. Compared with beta-lactam and sulfonamide antibiotics, tetracycline and quinolone antibiotics have longer environmental half-lives and are more widely used, particularly in agriculture, aquaculture, and healthcare. In this study, the composition, spatial distribution, potential sources, and ecological risks of 4 tetracycline and 20 quinolone antibiotics were systematically investigated by liquid chromatography tandem mass spectrometry (LC-MS/MS) in the surface seawater of the Northeastern Indian Ocean for the first time. A total of nine antibiotics were detected in seawater samples, including tetracycline (detection rate: 100%), oxytetracycline (100%), chlortetracycline (100%), doxycycline (100%), ofloxacin (100%), ciprofloxacin (100%), norfloxacin (92.3%), enrofloxacin (96.2%), and fleroxacin (23.1%). Tetracycline, oxytetracycline, chlortetracycline, doxycycline, ofloxacin, ciprofloxacin, norfloxacin, and enrofloxacin were widely distributed throughout the study area, with tetracycline antibiotics (83.8%) being significantly more prevalent than quinolone antibiotics. Among them, oxytetracycline was the dominant tetracycline antibiotic. The concentrations of tetracycline and quinolone antibiotics ranged from 0.258 to 23.521 ng l-1 (mean: 16.813 ng l-1) and 0.016-9.480 ng l-1 (mean: 3.261 ng l-1), respectively. The highest concentrations were found in the northeastern region of the study area. Aquaculture and livestock farming in Myanmar, Thailand, and Malaysia were identified as potential sources of these antibiotics. Ecological risk assessments indicated that ciprofloxacin poses a moderate risk to aquatic organisms in the Northeastern Indian Ocean. This study provides new insights into antibiotic pollution in the open waters of the Indian Ocean and highlights the urgent need for further research on the ecological impacts of these emerging pollutants in marine environments.

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.

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.

BACKGROUND Lignin is an important component of marine organic carbon. It is also an important biomarker for extracting information on the evolution of the land and marine environment and tracking the source of organic marine matter. However, the existing analytical techniques are difficult to determine lignin directly. So, the content of phenolic compounds in the decomposition products of lignin in marine sediments were generally determined to indicate the content of lignin and the source of organic matter. The content of phenolic compounds in the decomposition products of lignin in marine sediments is often used to reflect the content of lignin. In addition, by calculating the diagnostic ratio of individual phenolic compounds, it also provides important information about the classification, source, and diagenesis of terrestrial organic matter in marine sediments. However, phenolic compounds in the decomposition products of lignin have the characteristics of strong polarity and low volatility, so they cannot be directly detected by gas chromatography and need to be derivatized first, which makes the sample processing complicated and often results in incomplete derivatization. Therefore, it is of great significance to develop a simple and reliable method for determination of phenolic compounds of the lignin decomposition products in marine sediments to explore the source of organic matter and understand the environmental evolution process. OBJECTIVES To establish a simple and reliable method for the determination of phenolic compounds of lignin decomposition products in marine sediments using solid phase extraction (SPE) combined with ultra-high performance liquid chromatography-high resolution mass spectrometry, and to trace the content level and source of lignin in the sediments of Laizhou Bay in China. METHODS Marine sediment samples were first decomposed with oxidative-alkaline CuO and extracted by solid phase extraction. Briefly, the oxidation was carried out in a polytetrafluoroethylene digestion tank. 1.00g of sediment sample, 500mg of copper oxide, and 100mg of ammonium ferrous sulfate were accurately weighed and placed in the tank. The components were thoroughly mixed with the sample and then the digestion tank was transferred to a glove box filled with nitrogen. 8.0mL of aqueous sodium hydroxide solution with a concentration of 8.0% (bubbled with N2 to remove dissolved oxygen) was added to the tank. The digestion tank was covered tightly and transferred to an oven heating to 150℃ for reaction, which was terminated after 3h. After the digestion tank cooled to room temperature, it was carefully unscrewed, and an internal standard (ethyl vanillin) solution was added. Subsequently, the hydrolysate was transferred to a centrifuge tube, spun at 8000r/min for 10min, and the supernatant and reaction residue was separated. 2.0mL of 1.0% sodium hydroxide solution was added to rinse the residue, and centrifuged at 8000r/min for 10min. Combining the centrifuged supernatant obtained twice, the solution was acidified to pH=1 with hydrochloric acid. After the solution was left to stand for 30 minutes, solid phase extraction was performed. The SPE procedure was as follows: A hydrophilic-lipophilic balance (HLB) SPE cartridge (200mg, 6mL) was conditioned with 5mL of methanol and 5mL of ultrapure water. Sample solution was passed through the cartridge in a flow rate 1.0mL/min, and then the cartridges were rinsed with 10mL water, and dried under vacuum for about 3min. Phenolic compounds were eluted with 10mL ethyl acetate, and were evaporated by a rotary evaporator, reconstituted with sample solvent. Then, ultra-high performance liquid chromatography using ZORBAX Eclipse XDB-C18 column with packing particle size of 1.8μm was used to directly separate all target compounds at 28℃, with gradient elution. The mobile phase was composed of ultrapure water with 0.1% formic acid (V/V) and acetonitrile/methanol (9:1, V/V) , and the flow rate was set to 0.25mL/min. Electrospray ionization (in positive) time of flight mass spectrometry was applied to detect target compounds in full scan mode, and quantification was performed using an internal standard determination. RESULTS Firstly, chromatographic conditions and solid phase extraction conditions were systematically optimized. Ultra-high performance liquid chromatography was used for the chromatographic separation of phenolic compounds from lignin decomposition products in marine sediments. The separation effects of three mobile phase systems, namely, water-acetonitrile, water- methanol, and water-methanol-acetonitrile, were compared. When using a water-methanol -acetonitrile ternary mobile phase system, the resolution of various phenolic compounds was superior to the commonly used water-acetonitrile or water-methanol binary mobile phase systems in the literature. In addition, the effects of mobile phase acidity (trifluoroacetic acid, formic acid, and acetic acid were added into the mobile phase) on the separation of various phenolic compounds were investigated. The results showed that adding a certain concentration of all three acids to the mobile phase provided better separation results. Considering the compatibility with mass spectrometry, it was finally determined that adding 0.1% formic acid into the mobile phase achieved good peak patterns and resolution. In order to determine the ionization mode suitable for the analysis of phenolic compounds from lignin decomposition products in marine sediment, electrospray ionization (ESI) mass spectrometry was performed on each target phenolic compound in ESI+ and ESI− mode, respectively. Under ESI+ mode, various target phenolic compounds were less affected by interfering substances in the sample matrix, and the MS response value for most of the phenolic compounds was higher than that found in ESI− mode. Hence, ESI-TOF/MS in positive mode was selected to determine phenolic compounds of lignin decomposition products in marine sediment. Subsequently, the fragmentation voltage was optimized to obtain the highest sensitivity for all target phenolic compounds, which was the main mass spectrometric condition that affected the quantification accuracy and sensitivity. The effect of fragmentation voltage on the MS response signal of each target phenolic compound was investigated in the range of 80V to 200V. Overall, considering the detection sensitivity of the [M+H]+ ion peak of each target compound, 130V was selected as the optimal fragmentation voltage to determine phenolic compounds of lignin decomposition products in marine sediment. The effect of pH (1.0-2.5) of the loading solution for solid phase extraction on the extraction efficiency of various target phenolic compounds was systematically investigated, to ensure that the phenolic compounds of lignin decomposition products in marine sediments have a good recovery rate during the SPE process. When the pH of the loading solution was 1.0 and 1.5, the recovery rate of various phenolic compounds by using HLB solid phase extraction column was significantly higher than that of the loading solution adjusted pH to 2.0 and 2.5. When the pH of the sample solution was 1.0 and 1.5, although the recoveries of syringaldehyde and acetovanillone were relatively similar, the recoveries of other phenolic compounds were the highest at a pH of 1.0. Considering the recovery rate of all the target phenolic compounds and applicability of the method, the pH of the sample solution was confirmed to adjust to 1.0. In this study, HLB SPE column with 200mg of packing material was used to enrich phenolic compounds in sample extraction solution. Generally, 5-10mL of eluting solvent can ensure the full elution of all target phenolic compounds adsorbed on the SPE column. Therefore, based on the results of literature research, ethyl acetate was finally selected as the eluting solvent, with a dosage of 10mL. Under the optimum experimental conditions, the 11 main decomposition phenol compounds of lignin in marine sediments were well separated within 20 minutes. The proposed method had good precision (RSD was less than 9.0%), the correlation coefficient (R2) was not less than 0.9989 in the linear range, and the recovery rate of all spiked phenol compounds in blank marine sediment was in the range of 86.8%-93.2%, thereby indicating that the developed method would be suitable to determine the target decomposition phenol compounds of lignin in marine sediment. Subsequently, the method was used to determine the phenolic compounds of lignin decomposition products in the surface sediments of Laizhou Bay. The detection rate of 11 target phenolic compounds in 12 surface sediment samples was 100%, and the concentration of Σ8 in 12 surface sediment samples ranged from 0.001mg/10gds to 0.019mg/10gds. The value of C/V was between 0.18 and 0.81, with an average of 0.38; the value of S/V was between 0.18 and 0.45, with an average of 0.26; PON/P value was between 0.01 and 0.07, with an average of 0.03; P/(V+S) value was between 0.55 and 3.77, with an average of 1.44; (Ad/Al)v value was between 0.12 and 1.07, with an average of 0.48; the value of (Ad/Al)s was between 0.15 and 1.26, with an average of 1.02. CONCLUSIONS The above diagnostic ratios indicate that the lignin in the surface sediments of Laizhou Bay originate mainly from the herbaceous tissue of angiosperms, while the proportion of organic matter in vascular plants is relatively low. The degradation degree of terrestrial organic matter in most sampling stations is medium or high, but there is still a small amount of fresh plant debris. The proposed method has the advantages of high efficiency, simple for sample pretreatment, and is a powerful technique for the determination of main decomposition product phenolic compounds of lignin in marine sediments.

Microplastics (MPs) and marine lipophilic phycotoxins (MLPs) are two classes of emerging contaminants. Together, they may exacerbate the negative impacts on nearshore marine ecosystems. Herein, the loading of 14 representative MLPs, closely related to toxin-producing algae, on MPs and their relations with colorful MPs have been explored for the first time based on both field and lab data. The objectives of our study are to explore the roles of multiple factors (waterborne MLPs and MP characteristics) in the loading of MLPs by MPs with the applications of various statistical means, and to further explore the role of the color of MP in the loading of specific MLPs through lab simulation experiments. Our results demonstrated that MPs color determined the loading of some specific MLPs on MPs and green MPs can load much more than other colorful fractions (p < 0.05). These interesting phenomena illustrated that the color effects on the loading processes of MLPs on MPs are a dynamic process, and it can be well explained by the shading effect of MP color, which may affect the growth and metabolism of the attached toxic-producing algae on MPs and hence the production of specific MLPs. Furthermore, loading of MLPs on MPs can be considered as the comprehensive physicochemical and biological processes. Our results caution us that special attention should be paid to explore the real-time dynamic color shading effects on all kinds of bio-secreted contaminants loading on MPs, and highlight the necessary to comprehensive investigate the interaction between biota, organic contaminants and MPs.

Hydrophilic cyanotoxins (HCTs), such as paralytic shellfish toxins (PSTs), anatoxin-a (ATX-a), and cylindrospermopsin (CYN) are highly toxic and toxin-producing algae are widely distributed worldwide. However, HCTs, especially PSTs, are rarely reported in freshwater due to analytical limitations. This may result in an underestimation of the ecological risks and health risks. This study developed a new method to detect ATX-a, CYN, and thirteen common PSTs in freshwater simultaneously by using off-line solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of detection (LODs) of all targets were lower than 0.05 μg/L, which could meet the regulatory requirements for monitoring of HCTs in drinking water in different countries and regions. To improve the detection sensitivities for trace PSTs, a method based on off-line SPE and on-line SPE-LC-MS/MS was established with LOD around 0.001 μg/L. GTX1&4, GTX2&3, and GTX5 were detected in freshwater in China for the first time, highlighting that overall communities are facing potential risks of exposure to various PSTs in China. High concentrations of ATX-a and CYN were also detected in freshwater from Northern China. The proposed method helps to understand the pollution status of HCT in water bodies, especially during the non-algal bloom period.

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

Domoic acid (DA) can poison or even be fatal to marine mammals, and poses a potential risk to human health via transmission through the food chain. The level of DA in seawater will affect the safety of seafood. Therefore, a powerful method for the detection of DA in seawater, especially in the coastal mariculture zone, is needed. In order to identify different concentration levels of DA in real seawater, in this study, a method was established for the determination of trace DA in seawater by SPE-LC-MS/MS. First, the LC-MS/MS instrument and sample pretreatment conditions were optimized. Subsequently, DA was separated on a 5 TC-C18 (2) analytical column (150 mm×4.6 mm, 5 μm), and multiple reaction monitoring (MRM) was conducted in the positive electrospray ionization mode. For off-line SPE, the HLB cartridge could enrich DA in seawater. The best enrichment of DA was obtained after adding 0.32 mL formic acid to an 80.0 mL seawater sample. Four on-line SPE columns from Agilent, namely, 5 TC-C18(2) (12.5 mm×4.6 mm, 5 μm), Zorbax Eclipse Plus-C18 (12.5 mm×2.1 mm, 5 μm), Zorbax Eclipse XDB-C8 (12.5 mm×2.1 mm, 5 μm), and PLRP-S (12.5 mm×2.1 mm, 15-20 μm), were tested to determine their suitability to trap DA from seawater samples. The 5 TC-C18 (2) column offered the best retention ability and good peak shape of DA, and was selected as the on-line SPE column. Validation was then performed to assess the sensitivity, linearity, matrix effects (MEs), recoveries, and precisions of the proposed method. After simple treatment of the seawater samples by filtration and acidification, 0.6 mL of the seawater sample was injected directly for on-line SPE-LC-MS/MS. The linearity was good, and ranged from 10.0 to 500.0 ng/L (correlation coefficient R2=0.9992). The limit of detection (LOD) and limit of quantification (LOQ) of DA were 4.0 and 10.0 ng/L, respectively, with good recovery (≥81.0%) and precision (RSDs≤4.2%) at three spiked levels in the blank seawater samples. After the DA in the 80.0 mL seawater sample was enriched by off-line SPE, a 0.6 mL sample was injected for on-line SPE-LC-MS/MS. The DA in the spiked blank seawater sample showed a good linear relationship in the range of 0.3-50.0 ng/L (R2=0.9990). The LOD and LOQ were 0.1 and 0.3 ng/L, respectively. The recoveries of DA at low, medium, and high spiked levels in the blank seawater samples were all ≥69.2%, and the RSDs were ≤4.4%. The MEs of DA with both methods were 18.3% and 13.7%, respectively, indicating that the ME was mild enough to be negligible. In summary, the proposed method is simple, sensitive, robust, and powerful for the detection of DA in inshore and offshore seawater.

The occurrence, spatiotemporal variations, influence factors and environmental risks of eight common neonicotinoids (NEOs), fipronil, and three fipronil metabolites (fipronil and its metabolites are collectively referred to as FIPs) in different seasons from the estuary to the inner area of Jiaozhou Bay, China were comprehensively investigated. First- and second-generation NEOs were found to be the predominant pesticides in this area. The average contents of ∑NEOs and ∑FIPs from the estuary to the inner bay decreased from 12.99 ng/L to 0.82 ng/L and from 1.10 ng/L to 0.17 ng/L, respectively. NEO and FIP concentrations were higher in summer and autumn. High ∑NEO content is distributed in main inflow rivers, such as Dagu River and Licun River, which are influenced by pesticide application. NEO concentrations in all rivers were high upstream and low downstream because of the influence of heavy rainfall and seawater dilution in summer. NEO concentrations were high along the coast and low at the mouth and center of Jiaozhou Bay in summer and autumn and evenly distributed in winter and spring. Temperature has a great influence on most NEOs and FIPs owing to its effect on their degradation. Nitrogen-containing nutrients have an important influence on the distribution of fipronil and acetamiprid, which may be due to the activity of nitrogen-containing functional groups in their structure. Only Licun River, Dagu River and Haibo river sewage treatment plant in summer posed a certain risk of chronic toxicity for NEOs using the new threshold established by the species sensitive distribution (SSD) method for Chinese native aquatic lives. These findings should arouse people's attention.

Phytosterol biomarkers in marine sediments are often used to indicate the source of the sedimentary organics in the ocean, and to reflect the evolution of marine ecosystem and environment. In this study, a novel method 14 simultaneous determination of common phytosterols in marine sediments by non-aqueous reversed-phase liquid chromatography-atmospheric pressure photoionization mass spectrometry ( LC-APPI-MS ) was established. First, the APPI-MS characteristics of phytosterols were clarified. Under the positive APPI mode, phytosterols tended to produce stable characteristic ion peaks such as [ M + H - H2O ](+) , [ M + H - H-2 ](+) and [ M + H - 2H(2) ](+) . In the process of APPI-MS2, abundant fragment ion peaks were produced mainly through i-heterolysis. Second, LC-APPI-MS conditions were optimized, and a reversed-phase C-18 column was used to separate phytosterols with pure methanol as mobile phase and toluene as APPI ionization dopant , which could realize high sensitivity of detection for phytosterols in sediments. Furthermore, the method showed strong matrix interference resistance ability , good linear relationship ( R-2 >= 0. 9990 ) , high recovery rate ( 86. 4% - 94. 9% ) and good repeatability ( RSDs >= 8. 3% ). Finally, the proposed method was applied to detect common phytosterols in the surface sediment of Laizhou Bay in China, and several sterols, such as brassicasterol , fucosterol and sitosterol, etc. , were detected in every sediment sample. The total concentration of sterols was 4. 21-12. 91 mu g/g, among which the concentration of sitosterol was the highest. To sum up , the developed LC-APPI-MS method was a powerful tool 14 determination of common phytosterols in marine sediments , with easy-operation and high sensitivity.

The dinoflagellate genus Alexandrium has been well known for causing paralytic shellfish poisoning (PSP) worldwide. Several non-PSP toxin-producing species, however, have shown to exhibit fish-killing toxicity. Here, we report the allelopathic activity of Alexandrium leei from Malaysia to other algal species, and its toxicity to finfish and zooplankton, via laboratory bioassays. Thirteen microalgal species that co-cultured with Al. leei revealed large variability in the allelopathic effects of Al. leei on the test algae, with the growth inhibition rates ranging from 0 to 100%. The negative allelopathic effects of Al. leei on microalgae included loss of flagella and thus the motility, damages of chain structure, deformation in cell morphology, and eventually cell lysis. The finfish experienced 100% mortality within 24 h exposed to the live culture (2000-6710 cells center dot mL-1), while the rotifer and brine shrimp exhibited 96-100% and 90-100% mortalities within 48 h when exposed to 500-6000 cells center dot mL-1 of Al. leei. The mortality of the test animals depended on the Al. leei cell density exposed, leading to a linear relationship between mortality and cell density for the finfish, and a logarithmic relationship for the two zooplankters. When exposed to the treatments using Al. leei whole live culture, cell-free culture medium, extract of algal cells in the f/2-Si medium, extract of methanol, and the re-suspended freeze-and-thaw algal cells, the test organisms (Ak. sanguinea and rotifers) all died at the cell density of 8100 cells center dot mL-1 within 24 h. Toxin analyses by HILIC-ESI-TOF/MS and LC-ESI-MS/MS demonstrated that Al. leei did not produce PSP-toxins and 13-desmethyl

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.

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.

海洋藻毒素是海洋有害藻产生的次级代谢产物,具有种类多、毒性强和生物蓄积性等特点,对海洋生态系统、海产养殖业以及人类健康会造成严重威胁.近年来,近海水环境中的海洋藻毒素已引起人们的广泛关注.通过对近海水环境中海洋藻毒素的富集技术、仪器分析方法和分布特征方面的研究进展进行归纳和总结发现:被动固相吸附和固相萃取技术是海水中海洋藻毒素的主要富集技术,结合液相色谱-质谱联用技术进行检测,是目前近海水环境中各类海洋藻毒素检测的最有效方法;多种海洋藻毒素在全球近海水环境中有分布,且欧洲近海海水中藻毒素种类最丰富、浓度也相对较高;在中国近海水环境中多种脂溶性藻毒素广泛分布.在全球气候变化以及近海污染不断加剧的背景下,海洋藻毒素对近海水环境的影响不容忽视,今后的研究方向将主要包括:重要养殖区海水中藻毒素的长期连续监测;海水中典型藻毒素的现场快速检测技术;近海水环境中海洋藻毒素的来源及其影响因素;典型海洋藻毒素的迁移转化规律及其生物可利用性等.

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.

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.

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. Sigma 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.

Domoic acid (DA), a type of hydrophilic toxin produced by marine diatoms, can cause memory loss, which poses a serious threat to marine culture and even human health. In this study, a new method was developed for the highly efficient accumulation and detection of trace DA in seawater by high performance liquid chromatography-ultraviolet detection/mass spectrometry (HPLC-UV/MS). In this method, a solid phase extraction disk made of sulfonated styrene-vinyl benzene copolymer was used for DA enrichment and purification from acidified seawater samples. A C-18 chromatographic column was employed for DA separation using acetonitrile-water solution (90%, V/V) containing 2 mmol/L ammonium acetate and 0. 1% (V/V) formic acid as mobile phase. Detection wavelength was set at 242 nm. Under optimal conditions, the average recovery could still maintain at 89. 3% with good precision (relative standard deviation (RSD) <= 4. 0%) while enrichment factor could reach up to 2000. The limit of detection (S/N= 3) was 2. 5 ng/L. The results showed that the HPLC-UV detection developed here could meet the sensitivity requirements of DA determination in real seawater samples. This method was used to determine the seawater samples obtained from East China Sea, and it was found that the DA content in two station seawater samples was up to 2. 7 mu g/L. This method was efficient in determination of the concentration of DA in coastal aquaculture seawater, with easy-operation and high sensitivity.