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Saxitoxins are potent neurotoxins originating the acute human neurological syndrome of paralytic shellfish poisoning (PSP) via bivalve vectors. The official testing method in the European Union, commonly known as the 'Lawrence method', involves pre-column oxidation steps. The Portuguese monitoring adopted the hydrogen peroxide oxidation screening approach for bivalves contaminated with Gymnodinium catenatum toxins, which can quantify chromatographically at once 6 out of 10 analogues commonly found in bivalves. Seasonal fluctuation in the fluorescence yield of calibration curves was observed across years in a consistent manner. It correlated with fluctuations in average monthly air temperature in Lisbon, highlighting the importance of recording the room temperature during the oxidation steps as a matter of routine practice. Incubation experiments also showed an increase in fluorescence yield with temperature, more pronounced for the 11-hydroxysulphate analogues (dcGTX2 + 3, C1 + 2, GTX2 + 3) than for the 11-H toxins (dcSTX, GTX5[B1], STX). Temperature can be exploited to increase fluorescence yield, assisting in spectral confirmation, but must not exceed 40–50 °C to avoid toxin decomposition or production of extra oxidation products. [ABSTRACT FROM AUTHOR]

The presence of zooplankton in marine ecosystems is an important factor affecting toxin production in dinoflagellates. However, whether the production of paralytic shellfish toxins (PSTs) by Gymnodinium catenatum and Alexandrium pacificum is affected by substances produced by zooplankton is not yet fully understood. This study assessed the effects of zooplankton extracts on cell abundance, pigment concentration and composition, chlorophyll-a-specific primary production (Chl-a SP), and PST production in G. catenatum and A. pacificum, isolated from Korean coastal waters. In addition, a novel group of hydroxybenzoate PSTs known as GC toxins, which lack commercial reference standards, was evaluated. No significant differences were observed in cell abundance, pigment composition, or Chl-a SP in the experimental group of G. catenatum strains exposed to zooplankton extracts compared to the control group. However, the production of PSTs, including GC toxins, was significantly enhanced when the strain was exposed to extracts of Calanus finmarchicus. Meanwhile, in the A. pacificum strain, some experimental groups showed significant differences in cell abundance and pigment composition, while Chl-a SP significantly decreased in all experimental groups. In addition, PST production was stimulated by the addition of C. finmarchicus extracts. No GC toxins were detected in the A. pacificum strain. This study demonstrated that substances derived from C. finmarchicus enhance the production of PSTs in G. catenatum and A. pacificum. Our findings will improve the current understanding of the occurrence and development mechanisms of PSTs in marine ecosystems and contribute to developing strategies to efficiently secure standard reference toxin products using toxic dinoflagellates. [ABSTRACT FROM AUTHOR]

Exposure to toxigenic harmful algal blooms (HABs) can result in widely recognized acute poisoning in humans. The five most commonly recognized HAB-related illnesses are diarrhetic shellfish poisoning (DSP), paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), neurotoxic shellfish poisoning (NSP), and ciguatera poisoning (CP). Despite being caused by exposure to various toxins or toxin analogs, these clinical syndromes share numerous similarities. Humans are exposed to these toxins mainly through the consumption of fish and shellfish, which serve as the main biological vectors. However, the risk of human diseases linked to toxigenic HABs is on the rise, corresponding to a dramatic increase in the occurrence, frequency, and intensity of toxigenic HABs in coastal regions worldwide. Although a growing body of studies have focused on the toxicological assessment of HAB-related species and their toxins on aquatic organisms, the organization of this information is lacking. Consequently, a comprehensive review of the adverse effects of HAB-associated species and their toxins on those organisms could deepen our understanding of the mechanisms behind their toxic effects, which is crucial to minimizing the risks of toxigenic HABs to human and public health. To this end, this paper summarizes the effects of the five most common HAB toxins on fish, shellfish, and humans and discusses the possible mechanisms. [ABSTRACT FROM AUTHOR]

Over the recent decades, an apparent worldwide rise in Harmful Algae Blooms (HABs) has been observed due to the growing exploitation of the coastal environment, the exponential growth of monitoring programs, and growing global maritime transport. HAB species like Alexandrium catenella—responsible for paralytic shellfish poisoning (PSP)—Protoceratium reticulatum, and Lingulaulax polyedra (yessotoxin producers) are a major public concern due to their negative socioeconomic impacts. The significant northward geographical expansion of A. catenella into more oceanic-influenced waters from the fjords where it is usually observed needs to be studied. Currently, their northern boundary reaches the 36°S in the Biobio region where sparse vegetative cells were recently observed in the water column. Here, we describe the environment of the Biobio submarine canyon using sediment and water column variables and propose how toxic resting cyst abundance and excystment are coupled with deep-water turbulence (10−7 Watt/kg) and intense diapycnal eddy diffusivity (10−4 m2 s−1) processes, which could trigger a mono or multi-specific harmful event. The presence of resting cysts may not constitute an imminent risk, with these resting cysts being subject to resuspension processes, but may represent a potent indicator of the adaptation of HAB species to new environments like the anoxic Biobio canyon. [ABSTRACT FROM AUTHOR]

The blooms of Alexandrium catenella, the main producer of paralytic shellfish toxins worldwide, have become the main threat to coastal activities in Southern Chile, such as artisanal fisheries, aquaculture and public health. Here, we explore retrospective data from an intense Paralytic Shellfish Poisoning outbreak in Southern Chile in Summer–Autumn 2016, identifying environmental drivers, spatiotemporal dynamics, and detoxification rates of the main filter-feeder shellfish resources during an intense A. catenella bloom, which led to the greatest socio-economic impacts in that area. Exponential detoxification models evidenced large differences in detoxification dynamics between the three filter-feeder species surf clam (Ensis macha), giant barnacle (Austromegabalanus psittacus), and red sea squirt (Pyura chilensis). Surf clam showed an initial toxicity (9054 µg STX-eq·100 g−1) around 10-fold higher than the other two species. It exhibited a relatively fast detoxification rate and approached the human safety limit of 80 µg STX-eq·100 g−1 towards the end of the 150 days. Ecological implications and future trends are also discussed. Based on the cell density evolution, data previously gathered on the area, and the biology of this species, we propose that the bloom originated in the coastal area, spreading offshore thanks to the resting cysts formed and transported in the water column. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PSTs) are potent neurotoxins produced by certain microalgae, particularly dinoflagellates, and they can accumulate in shellfish in coastal seawater and thus pose significant health risks to humans. To explore the relationship between toxicity and PST profiles in seawater and mussels, the spatiotemporal variations in PST concentrations and profiles were investigated along the southern coast of Korea under peak PST levels during spring. Seawater and mussel samples were collected biweekly from multiple stations, and the toxin concentrations in the samples were measured. Moreover, the dinoflagellate community composition was analyzed using next-generation sequencing to identify potential PST-producing species. The PST concentrations and toxin profiles showed substantial spatiotemporal variability, with GTX1 and GTX4 representing the dominant toxins in both samples, and C1/2 tending to be higher in seawater. Alexandrium species were identified as the primary sources of PSTs. Environmental factors such as water temperature and salinity influenced PST production. This study demonstrates that variability in the amount and composition of PSTs is due to intricate ecological interactions. To mitigate shellfish poisoning, continuous monitoring must be conducted to gain a deeper understanding of these interactions. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX), an exceptionally potent marine toxin for which no antidote is currently available, is produced by methanogens and cyanobacteria. This poses a significant threat to both shellfish aquaculture and human health. Consequently, the development of a rapid, highly sensitive STX detection method is of great significance. The objective of this research is to create a novel approach for identifying STX. Therefore, amplified luminescent proximity homogeneous assay (AlphaLISA) was established using a direct competition method based on the principles of fluorescence resonance energy transfer and antigen–antibody specific binding. This method is sensitive, rapid, performed without washing, easy to operate, and can detect 8–128 ng/mL of STX in only 10 min. The limit of detection achieved by this method is as low as 4.29 ng/mL with coefficients of variation for the intra-batch and inter-batch analyses ranging from 2.61% to 3.63% and from 7.67% to 8.30%, respectively. In conclusion, our study successfully establishes a simple yet sensitive, rapid, and accurate AlphaLISA method for the detection of STX which holds great potential in advancing research on marine biotoxins. [ABSTRACT FROM AUTHOR]

Consuming poisoned shellfish can lead to severe health problems and even death. Alexandrium catenella (Group I) and A. pacificum (Group IV) cause paralytic shellfish poisoning (PSP) in Korea, and PSP is detected more in a wider area. However, the association between toxic dinoflagellates and shellfish poisoning is unclear. Therefore, it is necessary to understand the toxicity, detoxification, and compositional differences in PSP in Mytilus edulis exposed to PSP caused by A. catenella and A. pacificum. High-performance liquid chromatography with post-column oxidation was used to analyze PSP toxicity in poisoned M. edulis. PSP in M. edulis increased as the A. catenella and A. pacificum cell density increased. However, the cell density of A. catenella peaked faster than that of A. pacificum, and a high level of toxicity was detected. In the detoxification experiment, PSP in M. edulis decreased rapidly within 24 h in filtered seawater. However, PSP was continuously detected without decreasing below the detection limit until the last day of the experiment. In addition, the carbamate composition (GTX1+4) was detected as the main toxic composition in poisoned M. edulis, unlike in vegetative cells. GTX1+4 can poison shellfish quickly when toxic dinoflagellates appear in the marine environment. However, poisoned shellfish take a long time to be completely detoxified. Moreover, if shellfish continuously feed on poisonous dinoflagellates, their toxicity can increase rapidly due to biotransformation. Our results can help identify the mechanisms of shellfish toxicity and detoxification after PSP caused by toxic dinoflagellates. [ABSTRACT FROM AUTHOR]

The changes in the cell physiology (growth rate, cell size, and cell DNA content), photosynthetic efficiency, toxicity, and sexuality under variable light and nutrient (phosphates) conditions were evaluated in cultures of the dinoflagellate Alexandrium minutum obtained from a red tide in the Ría de Vigo (NW Spain). The cells were grown at low (40 and 150 µE m−2 s−1), moderate (400 µE m−2 s−1), and high (800 µE m−2 s−1) light intensities in a medium with phosphate (P+) and without (P−). Cultures were acclimated to the irradiance conditions for one week, and the experiment was run for ~1 month. The cell size and DNA content were monitored via flow cytometry. Two different clonal strains were employed as a monoculture (in a P− or P+ medium) or, to foster sexuality and resting cyst formation, as a mixed culture (only in a P− medium). A. minutum growth was favored by increasing light intensities until 400 µE m−2 s−1. The DNA content analyses indicated the accumulation of S-phase cells at the highest light intensities (400 and 800 µE m−2 s−1) and therefore the negative effects on cell cycle progression. Only when the cells were grown in a P− medium did higher light intensities trigger dose-dependent, significantly higher toxicities in all the A. minutum cultures. This result suggests that the toxicity level is responsive to the combined effects of (high) light and (low) P stress. The cell size was not significantly affected by the light intensity or P conditions. The optimal light intensity for resting cyst formation was 150 µE m−2 s−1, with higher irradiances reducing the total encystment yield. Encystment was not observed at the lowest light intensity tested, indicative of the key role of low-level irradiance in gamete and/or zygote formation, in contrast to the stressor effect of excessive irradiance on planozygote formation and/or encystment. [ABSTRACT FROM AUTHOR]

The marine dinoflagellate Alexandrium is known to form harmful algal blooms (HABs) and produces saxitoxin (STX) and its derivatives (STXs) that cause paralytic shellfish poisoning (PSP) in humans. Cell growth and cellular metabolism are affected by environmental conditions, including nutrients, temperature, light, and the salinity of aquatic systems. Abiotic factors not only engage in photosynthesis, but also modulate the production of toxic secondary metabolites, such as STXs, in dinoflagellates. STXs production is influenced by a variety of abiotic factors; however, the relationship between the regulation of these abiotic variables and STXs accumulation seems not to be consistent, and sometimes it is controversial. Few studies have suggested that abiotic factors may influence toxicity and STXs-biosynthesis gene (sxt) regulation in toxic Alexandrium, particularly in A. catenella, A. minutum, and A. pacificum. Hence, in this review, we focused on STXs production in toxic Alexandrium with respect to the major abiotic factors, such as temperature, salinity, nutrients, and light intensity. This review informs future research on more sxt genes involved in STXs production in relation to the abiotic factors in toxic dinoflagellates. [ABSTRACT FROM AUTHOR]

Paralytic shellfish poisoning is an important concern for mollusk fisheries, aquaculture, and public health. In Galicia, NW Iberian Peninsula, such toxicity has been monitored for a long time using mouse bioassay. Therefore, little information exists about the precise toxin analogues and their possible transformations in diverse mollusk species and environments. After the change in the European PSP reference method, a refinement of the Lawrence method was developed, achieving a 75% reduction in chromatogram run time. Since the beginning of 2021, when this refinement Lawrence method was accredited under the norm UNE-EN ISO/IEC 17025, it has been used in the area to determine the toxin profiles and to estimate PSP toxicity in more than 4500 samples. In this study, we have summarized three years of monitoring results, including interspecific, seasonal, and geographical variability of PSP toxicity and toxin profile. PSP was detected in more than half of the samples analyzed (55%), but only 4.4% of the determinations were above the EU regulatory limit. GTX1,4 was the pair of STX analogs that produced the highest toxicities, but GTX2,3 was found in most samples, mainly due to the reduction of GTX1,4 but also by the higher sensitivity of the method for this pair of analogs. STX seems to be mainly a product of biotransformation from GTX2,3. The studied species (twelve bivalves and one gastropod) accumulated and transformed PSP toxins to a different extent, with most of them showing similar profiles except for Spisula solida and Haliotis tuberculata. Two seasonal peaks of toxicity were found: one in spring-early summer and another in autumn, with slightly different toxin profiles during outbreaks in relation to the toxicity during valleys. In general, both the total toxicity and toxin profiles of the southernmost locations were different from those in the northern part of the Atlantic coast and the Cantabrian Sea, but this general pattern is modified by the PSP history of some specific locations. [ABSTRACT FROM AUTHOR]

Alexandrium pacificum (A. pacificum) is a typical paralytic shellfish poisonous dinoflagellate. Harmful algal blooms (HABs) caused by this species can bring serious environmental problems and economic losses to the aquaculture industry. In this study, transcriptome sequencing and analyses were performed on the neural tissue of Litopenaeus vannamei (L. vannamei) after acute exposure to A. pacificum disrupted solution for 72 h, and differentially expressed genes (DEGs) were identified. The results showed that, compared with the control samples, 300 DEGs were identified in the experimental group, of which 194 were up-regulated, and 106 down-regulated. The gene ontology (GO) functional enrichment analysis showed that DEGs were significantly enriched in the cortical cytoskeleton organization, troponin complex, amylo-alpha-1,6-glucosidase and thymidine phosphorylase. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis found that DEGs were mainly enriched in the oxidative phosphorylation process, intercellular tight junctions and mitophagy. The results showed that the proteoglycans, signaling pathways, and various metabolic processes that regulate cell proliferation, differentiation, and apoptosis all played an essential role in the response of L. vannamei to A. pacificum toxins. [ABSTRACT FROM AUTHOR]

The article discusses the monitoring of harmful algal biotoxins in British Columbia coastal waters. It highlights the occurrence of a phytoplankton bloom in 2015 that contained species of the pennate diatom Pseudo-nitzschia, which produce the neurotoxin domoic acid. The article also mentions the establishment of the Marine Biotoxin Monitoring Program, which collects samples to analyze biotoxin levels in critical habitats for endangered Southern Resident Killer Whales and Pacific salmon. The program aims to assess the risks posed by toxic harmful algal blooms to marine life and their potential impact on future climate-related changes. [Extracted from the article]

Exposure to toxigenic harmful algal blooms (HABs) can result in widely recognized acute poisoning in humans. The five most commonly recognized HAB-related illnesses are diarrhetic shellfish poisoning (DSP), paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), neurotoxic shellfish poisoning (NSP), and ciguatera poisoning (CP). Despite being caused by exposure to various toxins or toxin analogs, these clinical syndromes share numerous similarities. Humans are exposed to these toxins mainly through the consumption of fish and shellfish, which serve as the main biological vectors. However, the risk of human diseases linked to toxigenic HABs is on the rise, corresponding to a dramatic increase in the occurrence, frequency, and intensity of toxigenic HABs in coastal regions worldwide. Although a growing body of studies have focused on the toxicological assessment of HAB-related species and their toxins on aquatic organisms, the organization of this information is lacking. Consequently, a comprehensive review of the adverse effects of HAB-associated species and their toxins on those organisms could deepen our understanding of the mechanisms behind their toxic effects, which is crucial to minimizing the risks of toxigenic HABs to human and public health. To this end, this paper summarizes the effects of the five most common HAB toxins on fish, shellfish, and humans and discusses the possible mechanisms.

Harmful algal blooms (HABs) in marine environments have significant adverse effects on public health, aquaculture and recreational activities. Surges of certain phytoplanktonic toxin-producing microalgae (mostly dinoflagellates or diatoms species) can induce Amnesic, Diarrhetic or Paralytic Shellfish Poisoning (ASP, DSP and PSP). Among HAB species, the genus Dinophysis leads to DSP in human consumers; this being the most recurrent problem in the Iberian Peninsula with the biggest economic impact on clam production and harvesting. While complete elimination of HABs is not feasible, timely implementation of appropriate measures can prevent their negative consequences. This is critical for aquaculture. Research on D. acuminata (dominant Dinophysis species in the North Atlantic) has been focused on ecophysiology and population dynamics, although with few modelling attempts. Weekly monitoring along the Portuguese coast since 2006 has revealed that D. acuminata thrives under spring/summer photosynthetically active radiation (PAR) coupled with water temperatures below 20°C, which typically coincide with the local upwelling regime. In order to advance this knowledge numerically, we developed a demographic model linking D. acuminata growth rate to PAR and sea surface temperature (SST). The 13-year (1-Jan-2006 to 31-Dec-2018) time-series of observations was closely fit by model forecasts. However, the model demonstrated limitations in issuing timely warnings of harmful proliferation of D. acuminata, failing to do so in 50% of cases, and issuing incorrect warnings in 5% of the cases. Furthermore, improving the odds of emitting timely warnings always worsened the odds of emitting false warnings, and vice-versa. To simultaneously improve both aspects, the modelling results clearly indicated the need of implementing both census/ projection intervals smaller than 7 days and a laboratory detection limit below 20 cell/L. The time resolution of the census and of the model proved to be the most limiting factor that must be addressed in order to improve numerical forecasting of HABs. [ABSTRACT FROM AUTHOR]

BACKGROUND: Paralytic shellfish poisoning caused by human consumption of shellfish fed on toxic algae is a public health hazard. It is essential to implement shellfish monitoring programs to minimize the possibility of shellfish contaminated by paralytic shellfish toxins (PST) reaching the marketplace. RESULTS: This paper proposes a rapid detection method for PST in mussels using near‐infrared spectroscopy (NIRS) technology. Spectral data in the wavelength range of 950–1700 nm for PST‐contaminated and non‐contaminated mussel samples were used to build the detection model. Near‐Bayesian support vector machines (NBSVM) with unequal misclassification costs (u‐NBSVM) were applied to solve a classification problem arising from the fact that the quantity of non‐contaminated mussels was far less than that of PST‐contaminated mussels in practice. The u‐NBSVM model performed adequately on imbalanced datasets by combining unequal misclassification costs and decision boundary shifts. The detection performance of the u‐NBSVM did not decline as the number of PST samples decreased due to adjustments to the misclassification costs. When the number of PST samples was 20, the G‐mean and accuracy reached 0.9898 and 0.9944, respectively. CONCLUSION: Compared with the traditional support vector machines (SVMs) and the NBSVM, the u‐NBSVM model achieved better detection performance. The results of this study indicate that NIRS technology combined with the u‐NBSVM model can be used for rapid and non‐destructive PST detection in mussels. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Shellfish poisoning is a common food poisoning. To comprehensively characterize proteome changes in the whole brain due to shellfish poisoning, Tandem mass tag (TMT)-based differential proteomic analysis was performed with a low-dose chronic shellfish poisoning model in mice. A total of 6798 proteins were confidently identified, among which 123 proteins showed significant changes (fold changes of >1.2 or <0.83, p < 0.05). In positive regulation of synaptic transmission, proteins assigned to a presynaptic membrane (e.g., Grik2) and synaptic transmission (e.g., Fmr1) changed. In addition, altered proteins in nervous system development were observed, suggesting that mice suffered nerve damage due to the nervous system being activated. Ion transport in model mice was demonstrated by a decrease in key enzymes (e.g., Kcnj11) in voltage-gated ion channel activity and solute carrier family (e.g., Slc38a3). Meanwhile, alterations in transferase activity proteins were observed. In conclusion, these modifications observed in brain proteins between the model and control mice provide valuable insights into understanding the functional mechanisms underlying shellfish poisoning. [ABSTRACT FROM AUTHOR]

The article discusses the threat of feed-, food-, water-, and plant-related toxins to animal and human health worldwide. It highlights the diverse range of toxins, including bacterial toxins, algal toxins, mycotoxins, and phytotoxins, and their impact on animals. The article also mentions the emerging nature of many phytotoxins, attributing this trend to climate change and the global trade in decorative plants. The Special Issue presented in the article covers various research topics related to plant toxins and feed-associated toxicants, including their determination, epidemiology, degradation methods, clinical signs, and pathologic changes. The article concludes with a list of contributions that discuss specific studies on mycotoxins, pesticide residues, gossypol degradation, plant identification, toxin profiles, and hypoglycin A poisoning. The Special Issue also includes review papers on emerging plant intoxications, the toxicity of house plants, and the co-exposure to mycotoxins. The conflicts of interest are declared, and a list of contributions with their respective authors and publication details is provided. [Extracted from the article]

Shellfish are filter feeders that can accumulate toxic algae and their related toxins, increasing risk when consumed. Shellfish toxins can directly affect the physiological activities of marine organisms and threaten the stability of marine ecosystems. Ultimately, these toxins pass through the food chain and can endanger human health and economic security. Globally, shellfish poisoning incidents have occurred in many countries. The Bohai Sea is a semi-enclosed inland sea, where severe eutrophication of the seawater has occurred in recent years, leading to harmful algal blooms. To date, no simultaneous surveillance of diarrhetic shellfish poisonings (DSP) and paralytic shellfish poisonings (PSP) have been reported in the Tangshan shellfish culture area.To better understand shellfish toxin pollution in the shellfish culture areas of Tangshan and the dietary and health risks to residents, Mactra veneriformis, Ruditapes philippinarum, Rapana venosa, Crassostrea gigas, Cyclina sinensis, Meretrix meretrix, Mercenaria mercenaria, and Azumapecten farreri were collected for toxin monitoring from the Tangshan shellfish culture areas in Bohai Sea from October 2019 to September 2020. A total of 34 samples were collected for each shellfish species. Each sample weighed approximately 3 kg. All samples were transported to the laboratory on ice. In the laboratory, samples were flushed with tap water to remove sand and silt and shucked to collect the soft tissue. The tissue was thoroughly homogenized with a household blender, and approximately 50 g of tissue from each sample was stored at –20 ℃ until required for analysis. Five DSP including okadaic acid (OA), dinophysistoxin 1 (DTX1), dinophysistoxin 2 (DTX2), yessotoxin (YTX), and azaspiracid 1 (AZA1), and 14 PSP including saxitoxin (STX), neosaxitoxin (NEO), gonyautoxin 1/4 (GTX1/4), gonyautoxin 2/3 (GTX2/3), decarbamoylsaxitoxin (dcSTX), decarbamoylneosaxitoxin (dcNEO), decarbamoylgonyautoxin 2/3 (dcGTX2/3), gonyautoxin 5 (GTX5), gonyautoxin 6 (GTX6), and N-sulfocarbamoyl toxin 1/2 (C1/2) were tested using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The detection limit of the DSP method was 5 μg/kg, and the detection limit of the PSP method was 10–20 μg/kg.The DSP toxins were not detected in any of the samples. Several PSP toxins were detected, including saxitoxin (STX), gonyautoxin 1 (GTX1), gonyautoxin 2 (GTX2), and decarbamoylgonyautoxin 3 (dcGTX3). The GTX1 levels were the highest overall PSP toxin at 537.95 μg/kg in April. The results revealed positive rates of PSP for R. philippinarum, C. gigas, M. meretrix, and M. mercenaria, which were 11.76%, 47.06%, 5.90%, and 8.82%, respectively. Of the toxins tested, none were detected in the remaining samples. The highest PSP toxin levels in the positive samples from R. philippinarum, C. gigas, M. meretrix, and M. mercenaria were 414.26, 532.57, 452.77 and 195.46 μg STXeq/kg, respectively. We ranked the species in order of highest to lowest PSP toxin levels as: C. gigas > M. meretrix > R. philippinarum > M. mercenaria. In general, the toxin content of the shellfish in this area was lower than the EU limit of 800 μg STXeq/kg. The composition of shellfish toxins is related to many factors, including the sampling location and collection time. The toxin accumulation capacity by shellfish is also affected by many factors, including water pollution, salinity, light intensity, and most importantly, the species and density of the toxic algae in the surrounding waters.The ecological risk assessment methods used in this study were the risk quotient method (RQ) and the point assessment method. The RQ method is primarily used for semi-quantitative risk assessments to determine whether the pollutant concentrations have harmful effects. The point assessment model is a dietary exposure assessment tool. We applied risk quotient and point assessment methods to determine risk. There was no safety risk in the consumption of shellfish harvested from the Tangshan coastal study area during the study period. According to the point assessment method, at this specific time it was safe to consume the shellfish as the toxin levels were low. This analysis indicated that the safe single intake quantity of shellfish during months with high levels of shellfish-enriched toxins was reduced. As the toxin levels accumulating in different shellfish tissues can vary greatly, each sampled tissue was analyzed separately. The results indicate when there is a high accumulation of shellfish toxins present, consumers should restrict their consumption to a single serving rather than regularly consuming shellfish as part of their daily diet. The safety risk assessment results indicate that the seven shellfish species posed no food safety risk during the study period.This study provides a scientific basis for improving shellfish management practices to ensure shellfish are safe for consumption. This study analyzed the effects of toxin residues in shellfish species; different seasons and different locations vary in toxin content and components. We recommended consumers regulate their consumption to avoid potential poisoning events. This study provides social, economic, and ecological benefits in promoting green and healthy aquaculture of shellfish products, by ensuring the safety of shellfish products for consumer health. However, continuous long-term monitoring of both phytoplankton and biotoxins are recommended to ensure the development of the shellfish aquaculture industry and to support consumer health.

Saxitoxin (STX), an exceptionally potent marine toxin for which no antidote is currently available, is produced by methanogens and cyanobacteria. This poses a significant threat to both shellfish aquaculture and human health. Consequently, the development of a rapid, highly sensitive STX detection method is of great significance. The objective of this research is to create a novel approach for identifying STX. Therefore, amplified luminescent proximity homogeneous assay (AlphaLISA) was established using a direct competition method based on the principles of fluorescence resonance energy transfer and antigen–antibody specific binding. This method is sensitive, rapid, performed without washing, easy to operate, and can detect 8–128 ng/mL of STX in only 10 min. The limit of detection achieved by this method is as low as 4.29 ng/mL with coefficients of variation for the intra-batch and inter-batch analyses ranging from 2.61% to 3.63% and from 7.67% to 8.30%, respectively. In conclusion, our study successfully establishes a simple yet sensitive, rapid, and accurate AlphaLISA method for the detection of STX which holds great potential in advancing research on marine biotoxins.

The changes in the cell physiology (growth rate, cell size, and cell DNA content), photosynthetic efficiency, toxicity, and sexuality under variable light and nutrient (phosphates) conditions were evaluated in cultures of the dinoflagellate Alexandrium minutum obtained from a red tide in the Ría de Vigo (NW Spain). The cells were grown at low (40 and 150 µE m−2 s−1), moderate (400 µE m−2 s−1), and high (800 µE m−2 s−1) light intensities in a medium with phosphate (P+) and without (P−). Cultures were acclimated to the irradiance conditions for one week, and the experiment was run for ~1 month. The cell size and DNA content were monitored via flow cytometry. Two different clonal strains were employed as a monoculture (in a P− or P+ medium) or, to foster sexuality and resting cyst formation, as a mixed culture (only in a P− medium). A. minutum growth was favored by increasing light intensities until 400 µE m−2 s−1. The DNA content analyses indicated the accumulation of S-phase cells at the highest light intensities (400 and 800 µE m−2 s−1) and therefore the negative effects on cell cycle progression. Only when the cells were grown in a P− medium did higher light intensities trigger dose-dependent, significantly higher toxicities in all the A. minutum cultures. This result suggests that the toxicity level is responsive to the combined effects of (high) light and (low) P stress. The cell size was not significantly affected by the light intensity or P conditions. The optimal light intensity for resting cyst formation was 150 µE m−2 s−1, with higher irradiances reducing the total encystment yield. Encystment was not observed at the lowest light intensity tested, indicative of the key role of low-level irradiance in gamete and/or zygote formation, in contrast to the stressor effect of excessive irradiance on planozygote formation and/or encystment.

ObjectiveThis study aimed to assess control measures regarding the epidemiological characteristics of food-borne disease outbreaks to guide future prevention measures and treatment methods.MethodsDescriptive epidemiological methods were used to retrospectively investigate poisoning events， and epidemiological characteristics were analyzed.ResultsA total of 55 incidents and three deaths were reported， of which 60% were in individuals aged over 50 years. The incidents were all caused by family meals， exhibiting distinct family clustering. The main clinical manifestations were abnormal liver function （54 cases， 98.2%）， nausea （36 cases， 65.5%）， fatigue （29 cases， 52.7%）， and partial numbness of the mouth and lip extremities （9 cases， 16.4%）. The food suspected to cause the disease was Bullacta exarata， of which paralytic shellfish poisoning was detected in six samples. After taking comprehensive prevention and control measures， the incident was brought under control.ConclusionThis is a food poisoning case study caused by the consumption of paralytic shellfish-poisoned snails. The presence of other pathogenic factors cannot be ruled out. It is suggested that related departments should strengthen education and monitor early warning symptoms.

Species of the dinoflagellate genus Alexandrium are marine and planktonic forms, widely distributed, and some are recognized to form harmful algal blooms and to produce saxitoxins causing Paralytic Shellfish Poisoning in humans, and other toxins. We studied the species composition of Alexandrium in tropical and subtropical coastal areas of the Mexican Pacific: from the southern Gulf of California to the Gulf of Tehuantepec. Eleven Alexandrium species were identified, described, and illustrated using light microscopy, and occasionally scanning electron microscopy for certain species. Additionally, the genetic characterization of seven strains and four species, was performed, using sequences of the D1/D2 LSU rDNA and ITS regions. We identified the species (morphospecies): Alexandrium affine, A. gaarderae, A. globosum, A. leei, A. margalefii, A. minutum, A. monilatum, A. pseudogonyaulax, A. tamarense, A. tamiyavanichii, and A. tropicale. Of these, A. affine, A. leei, A. minutum, A. monilatum, A. pseudogonyaulax, A. tamarense and A. tamiyavanichii have been widely recognized as harmful algae. Alexandrium gaarderae, A. globosum and A. tropicale are new records for the Mexican Pacific. This is the first morphological documentation of A. pseudogonyaulax. Future studies of the genus might increase its species richness if more cultures are established and metabarcoding approach is used. [ABSTRACT FROM AUTHOR]

DINOPHYSIS NUTRITIONAL SOURCES I Dinophysis i species are obligate mixotrophs that require ciliate prey (e.g., I Mesodinium i species), light, and nutrients for sustained growth (Hansen et al., [16]; Kim, Kim, et al., [22]). These two issues are dealt with and all available results related to I Dinophysis i and their toxins in the United States are reviewed in: "A survey of I Dinophysis i spp. and their potential to cause diarrhetic shellfish poisoning in coastal waters of the United States" (Ayache et al., [3]). A synoptic view of the current distribution of I Dinophysis i species and reported DSP events (Figure 1) confirms that occurrence of toxic outbreaks is determined by the composition (profile and content) of local strains and the shellfish species affected (Blanco, [4]). Species of I Dinophysis i produce diarrhetic toxins and pectenotoxins and frequently cause harvesting bans in intensive shellfish cultivation sites in Western Europe, Chile, Perú, and Japan (Reguera et al., [29]). [Extracted from the article]

Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for these toxins in shellfish flesh has been adopted by many countries. In a recent study, mice were dosed with saxitoxin and tetrodotoxin mixtures daily for 28 days showing toxicity at low concentrations, which appeared to be at odds with other work. To further investigate this reported toxicity, we dosed groups of mice with saxitoxin and tetrodotoxin mixtures daily for 21 days. In contrast to the previous study, no effects on mouse bodyweight, food consumption, heart rate, blood pressure, grip strength, blood chemistry or hematology were observed. Furthermore, no histological findings were associated with dosing in this trial. The dose rates in this study were 2.6, 3.8 and 4.9 times greater, respectively, than the highest dose of the previous study. As rapid mortality in three out of five mice was observed in the previous study, the deaths are likely to be due to the methodology used rather than the shellfish toxins. To convert animal data to that used in a human risk assessment, a 100-fold safety factor is required. After applying this safety factor, the dose rates used in the current study were 3.5, 5.0 and 6.5 times greater, respectively, than the acute reference dose for each toxin type set by the European Union. Furthermore, it has previously been proposed that tetrodotoxin be included in the paralytic shellfish poisoning suite of toxins. If this were done, the highest dose rate used in this study would be 13 times the acute reference dose. This study suggests that the previous 28-day trial was flawed and that the current paralytic shellfish toxin regulatory limit is fit for purpose. An additional study, feeding mice a diet laced with the test compounds at higher concentrations than those of the current experiment, would be required to comment on whether the current paralytic shellfish toxin regulatory limit should be modified. [ABSTRACT FROM AUTHOR]

Many communities in Southeast Alaska harvest shellfish such as mussels and clams as an important part of a subsistence or traditional diet. Harmful algal blooms (HABs) of phytoplankton such as Alexandrium spp. produce toxins that can accumulate in shellfish tissues to concentrations that can pose a hazard for human health. Since 2013, several tribal governments and communities have pooled resources to form the Southeast Alaska Tribal Ocean Research (SEATOR) network, with the goal of minimizing risks to seafood harvest and enhancing food security. SEATOR monitors toxin concentrations in shellfish and collects and consolidates data on environmental variables that may be important predictors of toxin levels such as sea surface temperature and salinity. Data from SEATOR are publicly available and are encouraged to be used for the development and testing of predictive algorithms that could improve seafood risk assessment in Southeast Alaska. To date, more than 1700 shellfish samples have been analyzed for paralytic shellfish toxins (PSTs) in more than 20 locations, with potentially lethal concentrations observed in blue mussels (Mytilus trossulus) and butter clams (Saxidomus gigantea). Concentrations of PSTs exhibit seasonality in some species, and observations of Alexandrium are correlated to sea surface temperature and salinity; however, concentrations above the threshold of concern have been found in all months, and substantial variation in concentrations of PSTs remain unexplained.

The Galician Rías (NW Iberian Peninsula) are an important shellfish aquaculture area periodically affected by toxic episodes often caused by dinoflagellates such as Dinophysis acuminata and Alexandrium minutum, among others. In turn, water discolorations are mostly associated with non-toxic organisms such as the heterotrophic dinoflagellate Noctiluca scintillans, a voracious non-selective predator. The objective of this work was to study the biological interactions among these dinoflagellates and their outcome in terms of survival, growth and toxins content. To that aim, short experiments (4 days) were carried out on mixed cultures with N. scintillans (20 cells mL−1) and (i) one strain of D. acuminata (50, 100 and 500 cells mL−1) and (ii) two strains of A. minutum (100, 500 and 1000 cells mL−1). Cultures of N. scintillans with two A. minutum collapsed by the end of the assays. Both D. acuminata and A. minutum exposed to N. scintillans arrested its growth, though feeding vacuoles in the latter rarely contained any prey. Toxin analyses at the end of the experiment showed an increase in intracellular OA levels in D. acuminata and a significant reduction in PSTs in both A. minutum strains. Neither OA nor PSTs were detected in N. scintillans. Overall, the present study indicated that the interactions among them were ruled by negative allelopathic effects. [ABSTRACT FROM AUTHOR]

The armoured dinoflagellate Alexandrium can be found throughout many of the world's temperate and tropical marine environments. The genus has been studied extensively since approximately half of its members produce a family of potent neurotoxins, collectively called saxitoxin. These compounds represent a significant threat to animal and environmental health. Moreover, the consumption of bivalve molluscs contaminated with saxitoxin poses a threat to human health. The identification of Alexandrium cells collected from sea water samples using light microscopy can provide early warnings of a toxic event, giving harvesters and competent authorities time to implement measures that safeguard consumers. However, this method cannot reliably resolve Alexandrium to a species level and, therefore, is unable to differentiate between toxic and non-toxic variants. The assay outlined in this study uses a quick recombinase polymerase amplification and nanopore sequencing method to first target and amplify a 500 bp fragment of the ribosomal RNA large subunit and then sequence the amplicon so that individual species from the Alexandrium genus can be resolved. The analytical sensitivity and specificity of the assay was assessed using seawater samples spiked with different Alexandrium species. When using a 0.22 µm membrane to capture and resuspend cells, the assay was consistently able to identify a single cell of A. minutum in 50 mL of seawater. Phylogenetic analysis showed the assay could identify the A. catenella, A. minutum, A. tamutum, A. tamarense, A. pacificum, and A. ostenfeldii species from environmental samples, with just the alignment of the reads being sufficient to provide accurate, real-time species identification. By using sequencing data to qualify when the toxic A. catenella species was present, it was possible to improve the correlation between cell counts and shellfish toxicity from r = 0.386 to r = 0.769 (p ≤ 0.05). Furthermore, a McNemar's paired test performed on qualitative data highlighted no statistical differences between samples confirmed positive or negative for toxic species of Alexandrium by both phylogenetic analysis and real time alignment with the presence or absence of toxins in shellfish. The assay was designed to be deployed in the field for the purposes of in situ testing, which required the development of custom tools and state-of-the-art automation. The assay is rapid and resilient to matrix inhibition, making it suitable as a potential alternative detection method or a complementary one, especially when applying regulatory controls. [ABSTRACT FROM AUTHOR]

Algal blooms formed by some phytoplankton species can produce toxins or alter environmental conditions that can affect aquatic organisms and water quality, with impacts on the aquaculture and fisheries industries that can pose a risk to public health. The ABSa15 cell line and fish erythrocytes were the most sensitive to these extracts (up to 74.5% loss of viability and 100% haemolysis, respectively), confirming the haemolytic and cytotoxic effects of this dinoflagellate [[19]]. A previous study confirmed the sensitivity of the RTgill-W1 cells towards the two brevetoxins PbTx-2 and PbTx-3 purified from I K. brevis i , the karlotoxin KmTx-2 from the dinoflagellate I Karlodinium veneficum i , and paralytic shellfish toxins from I Alexandrium i spp. [[28], [31]], confirming the suitability of this assay for I in vitro i - I in vivo i correlations. 34564605 36 Industry - Aquaculture New ZealandAvailable online: https://www.aquaculture.org.nz/resources/general(accessed on 7 May 2023) 37 Rolton A., Rhodes L., Hutson K.S., Biessy L., Bui T., Mackenzie L., Symonds J.E., Smith K.F. Effects of Harmful Algal Blooms on Fish and Shellfish Species: A Case Study of New Zealand in a Changing Environment. [Extracted from the article]

Pyrodinium bahamense blooms reaching and exceeding 105 cells L-1 occur nearly every summer in Tampa Bay, Florida, USA. These high biomass blooms can reduce light penetration, degrade water quality, and deplete dissolved oxygen. In addition, this alga produces potent neurotoxins (saxitoxins) that can accumulate in filter-feeding shellfish and cause paralytic shellfish poisoning in humans if contaminated shellfish are consumed. Variability in toxicity of two alternate life history stages (vegetative cells and resting cysts) of P. bahamense can have implications for resource management. Here we discuss the saxitoxin composition and concentration observed in vegetative cells and resting cysts of P. bahamense collected from Tampa Bay. Analysis of bloom samples and cysts collected from Tampa Bay confirmed the presence of three saxitoxin congeners: decarbamoylsaxitoxin (dcSTX), gonyautoxin 5 (GTX5), and saxitoxin (STX) and showed that in general, vegetative cells in this area may be more toxic than resting cysts. In samples collected on 10 days throughout a laboratory growth experiment on a single isolate, the average total cellular toxin was 0.2 ± 0.02 pmol cell-1. In contrast, the average total cellular toxin in vegetative cells from bloom samples collected from 9 locations during peak bloom was 0.02 ± 0.002 pmol cell-1 and the concentration in resting cyst from one sediment sample 0.003 pmol cyst-1. [ABSTRACT FROM AUTHOR]

Shellfish poisoning is a common food poisoning. To comprehensively characterize proteome changes in the whole brain due to shellfish poisoning, Tandem mass tag (TMT)-based differential proteomic analysis was performed with a low-dose chronic shellfish poisoning model in mice. A total of 6798 proteins were confidently identified, among which 123 proteins showed significant changes (fold changes of >1.2 or p < 0.05). In positive regulation of synaptic transmission, proteins assigned to a presynaptic membrane (e.g., Grik2) and synaptic transmission (e.g., Fmr1) changed. In addition, altered proteins in nervous system development were observed, suggesting that mice suffered nerve damage due to the nervous system being activated. Ion transport in model mice was demonstrated by a decrease in key enzymes (e.g., Kcnj11) in voltage-gated ion channel activity and solute carrier family (e.g., Slc38a3). Meanwhile, alterations in transferase activity proteins were observed. In conclusion, these modifications observed in brain proteins between the model and control mice provide valuable insights into understanding the functional mechanisms underlying shellfish poisoning.

The more frequent occurrence of marine harmful algal blooms (HABs) and recent problems with newly-described toxins in Puget Sound have increased the risk for illness and have negatively impacted sustainable access to shellfish in Washington State. Marine toxins that affect safe shellfish harvest because of their impact on human health are the saxitoxins that cause paralytic shellfish poisoning (PSP), domoic acid that causes amnesic shellfish poisoning (ASP), diarrhetic shellfish toxins that cause diarrhetic shellfish poisoning (DSP) and the recent measurement of azaspiracids, known to cause azaspiracid poisoning (AZP), at low concentrations in Puget Sound shellfish. The flagellate, Heterosigma akashiwo, impacts the health and harvestability of aquacultured and wild salmon in Puget Sound. The more recently described flagellates that cause the illness or death of cultivated and wild shellfish, include Protoceratium reticulatum, known to produce yessotoxins, Akashiwo sanguinea and Phaeocystis globosa. This increased incidence of HABs, especially dinoflagellate HABs that are expected in increase with enhanced stratification linked to climate change, has necessitated the partnership of state regulatory programs with SoundToxins, the research, monitoring and early warning program for HABs in Puget Sound, that allows shellfish growers, Native tribes, environmental learning centers and citizens, to be the "eyes on the coast". This partnership enables safe harvest of wholesome seafood for consumption in the region and helps to describe unusual events that impact the health of oceans, wildlife and humans. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PSTs) are biotoxins derived from harmful algal blooms and cause paralytic shellfish poisoning (PSP). PSTs are widely found in natural waters, indicating that they can cause human death through food chain and economic losses of aquatic species worldwide. Therefore, accurate, sensitive, and efficient methods are needed for the detection of PSTs in the environment and food. Biosensor is one of the fastest-growing detection methods since they are simple, sensitive, portable, and efficient for real-time or near real-time analyses. This article provides a comprehensive review of PSTs biosensors by highlighting different signaling mechanisms (electrochemical, optical, etc.). Typically, the effects of the generation of bio-recognition elements on PSTs sensing performance to expand new biosensors applications which were highlighted. Although mouse bioassay and HPLC are the current methods used for PSTs detection, biosensor could become an alternative method for PSTs detection in the future. Although antibodies are the most popular affinity-based recognition elements, aptamers have been rapidly developed in recent years to mimic antibodies. As a result, biosensor detection of PSTs mainly focuses on electrochemical and optical signal transduction. Nonetheless, robust, accurate, and portable biosensors are needed for real application and commercialization. [Display omitted] • MerIts and demerits of bio-recognition elements for detceting PSTs were summarized. • Recent advanced biosensors methods for paralytic shellfish toxins was reviewed. • Electrochemical and optical signal transduction based biosensors had been strengthen. • AntiBodies and adaptors showed potential for development of practical biosensors. [ABSTRACT FROM AUTHOR]

Pyrodinium bahamense var compressum is a harmful dinoflagellate that produces saxitoxin, which causes paralytic shellfish poisoning (PSP) that is deadly to humans. A non-axenic culture of P. bahamense was established using f/2 media from samples collected from Sepanggar Bay, Kota Kinabalu, Sabah. Toxin analyses of cultures harvested on days 60, 120, 180, and 360 were performed using high-performance liquid chromatography with a fluorescence detector and compared with samples collected at the same location during the bloom in 2021. The highest cell toxin content was found in the bloom sample (86.2 fmole/ cell), and no toxin was detected in the culture 60 days old. In addition, cell toxin content for the P. bahamense culture was low (9.4-16.5 fmole/cell). Based on the toxin profile, P. bahamense comprises 84-98% of gonyautoxin 4. In summary, the current findings add to the existing knowledge of the toxin profiling of P. bahamense, a toxic, harmful algal bloom species, thus, leading to better toxin management. [ABSTRACT FROM AUTHOR]

Outbreaks of paralytic shellfish poisoning caused by the toxic dinoflagellate Alexandrium catenella (Dinophyceae) are currently a serious global problem both from economic and food hygiene perspectives. In Chile, A. catenella was first recorded in 1972 and is currently the main harmful algae species in the country, in terms of seafood security. As no relevant microsatellite markers for Chilean A. catenella populations were available, we isolated 23 new polymorphic microsatellite loci of A. catenella from Chile, of which 15 are applicable to both Chilean and Japanese populations. We found a strong genetic break between Chilean and Japanese A. catenella populations (FST=0.298, P<0.001), consistent with the morphological differences between them. In contrast to the Japanese population, for which genetic diversity ranged from 0.268 to 0.937, the Chilean population had a lower genetic diversity, ranging between 0.065 and 0.512. This study successfully developed A. catenella microsatellite markers that can be used to investigate its genetic spatial and temporal bloom diversity and assess further genetic connectivity between the population from southern and northern Chilean areas. [ABSTRACT FROM AUTHOR]

• Saxitoxin biosynthetic enzyme, SxtG, localizes to chloroplasts. • The PST-negative subclone of Alexandrium catenella expresses active SxtG but not SxtA. • The first in vitro reproduction of the early step of STX biosynthesis in dinoflagellates. Paralytic shellfish poisoning is caused by saxitoxin (STX), and its analogues (paralytic shellfish toxins (PSTs)) produced by marine dinoflagellates. SxtA and SxtG are the most essential enzymes in STX biosynthesis. Previous studies investigated the abundance and subcellular localization (i.e. , chloroplasts) of SxtA in dinoflagellates using immunostaining. The present study characterized SxtG, and positive signals were detected in sister subclones of Alexandrium catenella (Group I) with extremely different levels of PSTs. Multiplex fluorescence immunostaining detection of a PST-positive subclone revealed co-localization of SxtA and SxtG, suggesting that SxtG localizes to chloroplasts. In vitro amidino-transfer from arginine to Int-A', the first intermediate product in the biosynthesis, was presumed to be catalyzed by SxtG, and the reaction was established using crude extracts of PST-positive and negative A. catenella subclones. These analyses suggested that the PST-negative subclone expresses active SxtG but not SxtA. These findings support our hypothesis that decrease of SxtA leads to the loss of toxicity in the PST-negative subclone of A. catenella. Our results identified a key reaction that could enhance understanding of the biochemistry of STX biosynthesis in dinoflagellates. [Display omitted] [ABSTRACT FROM AUTHOR]

One way to resolve the paralytic shellfish poisoning problem is to reduce the number of causative plankton cysts through dredging. However, due to the long-term survival capabilities of Alexandrium cysts, suppressing germination remains a challenge, particularly in areas where these cysts are buried deep within sediments. This challenge could be mitigated by utilizing macrobenthic organisms, specifically deposit feeders, which are capable of ingesting ellipsoidal Alexandrium cysts. In this study, we examined whether three macrobenthic organisms collected from Ofunato Bay, along the Pacific coast of northern Japan, influence the abundance and germination of ellipsoidal Alexandrium cysts through ingestion experiments. The cyst counts in the sediments from ingestion experiments with Thyasira tokunagai (Mollusca) and Maldanidae sp. (Annelida) remained unchanged compared to the control, whereas a significant reduction was observed in the sediments from ingestion experiments with Theora lata (Mollusca). The digestion rate of ellipsoidal Alexandrium cysts by T. lata amounted to 375 cysts per individual per day. Moreover, the germination percentage in the presence of all three macrobenthic organisms declined compared to the control. These findings suggest that T. lata, which are highly concentrated in Ofunato Bay, are effective at removing ellipsoidal Alexandrium cysts and suppressing their germination. [ABSTRACT FROM AUTHOR]

San Francisco Bay (SFB) is a eutrophic estuary that harbors both freshwater and marine toxigenic organisms that are responsible for harmful algal blooms. While there are few commercial fishery harvests within SFB, recreational and subsistence harvesting for shellfish is common. Coastal shellfish are monitored for domoic acid and paralytic shellfish toxins (PSTs), but within SFB there is no routine monitoring for either toxin. Dinophysis shellfish toxins (DSTs) and freshwater microcystins are also present within SFB, but not routinely monitored. Acute exposure to any of these toxin groups has severe consequences for marine organisms and humans, but chronic exposure to sub-lethal doses, or synergistic effects from multiple toxins, are poorly understood and rarely addressed. This study documents the occurrence of domoic acid and microcystins in SFB from 2011 to 2016, and identifies domoic acid, microcystins, DSTs, and PSTs in marine mussels within SFB in 2012, 2014, and 2015. At least one toxin was detected in 99% of mussel samples, and all four toxin suites were identified in 37% of mussels. The presence of these toxins in marine mussels indicates that wildlife and humans who consume them are exposed to toxins at both sub-lethal and acute levels. As such, there are potential deleterious impacts for marine organisms and humans and these effects are unlikely to be documented. These results demonstrate the need for regular monitoring of marine and freshwater toxins in SFB, and suggest that co-occurrence of multiple toxins is a potential threat in other ecosystems where freshwater and seawater mix.

The receptor-binding assay (RBA) method for the detection of paralytic shellfish poisoning (PSP) toxins was evaluated for its overall performance in comparison with the mouse bioassay (MBA). An initial study to evaluate the effects of filtering shellfish extracts prior to running the RBA indicated no significant difference between filtered and unfiltered extracts on the determined saxitoxin (STX) concentrations. Next, we tested the RBA assay on 295 naturally contaminated mussel tissue samples, ranging in concentrations from 320 µg STX equiv. kg-1 to 13,000 µg STX equiv. kg-1 by MBA. An overall trend was observed with the RBA giving higher results (256 µg STX equiv. kg-1 on average) than the MBA; however, at low concentrations (< 500 µg STX equiv. kg-1) the RBA results were marginally lower. A third study was conducted using spiked mussel tissue analysed by three independent laboratories, two of which performed the RBA and one the MBA. This multi-laboratory study again showed the RBA to give higher results than the MBA; however, it also revealed that STX determination was accurate by the RBA, unlike the MBA. To optimise the assay for efficient usage under regulatory practice, three suggestions have been made: the use of an initial screening plate to separate those samples that exceed the alert level; use of rapid PSP test kits in the field and in the laboratory for screening negative samples and for early detection of toxicity; and use of an alternate commercially available porcine membrane in place of the laboratory-prepared rat membrane homogenate. The large number of samples analysed and the diversity of the tests conducted in this study further support the RBA as an affordable rapid method for STX detection that is also free of the routine sacrifice of live animals.

Twenty-five years of paralytic shellfish poisoning (PSP) toxicity in Galician bivalves have been studied. PSP was detected in 4785 out of 73,740 samples of the commercially important bivalve species analyzed from 1995 to 2020. Its general prevalence in the area was 6.5%. Only 1.6% of all samples tested were over the regulatory limit (incidence). The maximum level of PSP in the area, 40,800 µg STX 2HCl-eq kg−1, was recorded in raft mussels from Bueu (PON-II, Pontevedra) in December 2005. The highest maximum PSP values were found in mussels, which were mostly affected by Gymnodinium catenatum, but not those of prevalence and incidence which were recorded in clams, mostly affected by Alexandrium. Average levels in mussels were higher than in any other studied species. Spatially, in general, the prevalence, incidence, maximum, and average PSP toxicity during episodes tend to decrease from south to northeast, but some hot points with high levels can be identified. PCA analysis separates the southern rías, associated to G. catenatum blooms, from the middle and northern ones, associated to Alexandrium blooms. Along the year, two main peaks of the four variables are observed, the first one in late autumn–winter and the other in summer, the summer peak being much more important for the infaunal species than for raft mussels. In the seasonal pattern obtained by time series analysis of the average PSP toxicity, the autumn-winter peak was only maintained (and very reduced) in the southern rías, indicating that this peak is seasonally much less important than the summer peak. The observed seasonality is expected based on the timing of the blooms of the two PSP-producing phytoplankton groups present in the area. Over the 25 years of monitoring, large differences in PSP toxicity have been observed. Apart from some special years, an ascending trend in prevalence and incidence seems to be present from 2011 to 2020. No trend seems to exist during the same period for average or maximum toxicity. [ABSTRACT FROM AUTHOR]

American bullfrog (Rana castesbeiana) saxiphilin (RcSxph) is a high-affinity "toxin sponge" protein thought to prevent intoxication by saxitoxin (STX), a lethal bisguanidinium neurotoxin that causes paralytic shellfish poisoning (PSP) by blocking voltage-gated sodium channels (Nays). How specific RcSxph interactions contribute to STX binding has not been defined and whether other organisms have similar proteins is unclear. Here, we use mutagenesis, ligand binding, and structural studies to define the energetic basis of Sxph:STX recognition. The resultant STX "recognition code" enabled engineering of RcSxph to improve its ability to rescue Nays from STX and facilitated discovery of 10 new frog and toad Sxphs. Definition of the STX binding code and Sxph family expansion among diverse anurans separated by ~ 140 My of evolution provides a molecular basis for understanding the roles of toxin sponge proteins in toxin resistance and for developing novel proteins to sense or neutralize STX and related PSP toxins. [ABSTRACT FROM AUTHOR]

Gymnodinium catenatum has been the main species responsible for paralytic shellfish poisoning events along the Portuguese coast (Iberian Peninsula), causing bans on bivalve harvesting that result in huge economic losses. This work presents the characterization of two novel isolates of G. catenatum regarding their growth and toxin profiles. Laboratory growth experiments revealed that, although low growth rates were obtained during cultivation, the cell yields were high compared to those reported in the literature. Evaluation of the toxin profiles, by HPLC-FLD, essentially confirmed the typical composition of toxins of this regional population (Iberian Peninsula), namely, the absence or low representation of the toxins dcNEO, GTX1,4 and NEO and a higher ratio of the toxins C1,2, GTX6 and GTX5. However, the percentage of the identified toxins varied among the strains of this study (under the same isolation, growth, and analysis conditions), and also differed from that of other strains described in the literature. Interestingly, we found a comparatively high abundance of dcSTX in both strains, relative to the other toxins, and an unquantifiable amount of C3,4 toxins. In addition to the geographic relationship between toxin profiles, chemical conversions among toxins may explain some differences encountered in the toxin profiles of G. catenatum strains. [ABSTRACT FROM AUTHOR]

In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and hydrophilic toxins. Water temperature, salinity, hydrogen potential, dissolved oxygen saturation, inorganic nutrients and phytoplankton abundance were also determined. Two samples filtered through glass fiber filters were used for the extraction and analysis of paralytic shellfish toxins (PSTs) by lateral flow immunochromatography (IFL), HPLC with post-column oxidation and fluorescent detection (FLD) and UHPLC coupled to tandem mass spectrometry (UHPLC-MS/MS). Elevated nutrient contents were associated with the sites of rainwater discharge or those near anthropogenic activities. A predominance of the dinoflagellate Pyrodinium bahamense was found with abundances of up to 104 cells L−1. Identification of the dinoflagellate was corroborated by light and scanning electron microscopy. Samples for toxins were positive by IFL, and the analogs NeoSTX and STX were identified and quantified by HPLC-FLD and UHPLC-MS/MS, with a total PST concentration of 6.5 pg cell−1. This study is the first report that confirms the presence of PSTs in P. bahamense in Mexican waters of the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Simple Summary: Harmful algal blooms present a particular risk for marine ecosystems and human health alike. In this sense, it is important to accurately predict how toxin-producing microalgae could be affected by future climate change. The present study applied species distribution models (SDMs) to project the potential changes in the habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2040/50 and 2090/2100, across four different greenhouse gas emission scenarios, and using four abiotic predictors (i.e., sea surface temperature, salinity, current velocity, and bathymetry). In general, considerable contractions were observed for all three species in the lower latitudes of their distribution, together with projected expansions into higher latitudes, particularly in the Northern Hemisphere. This study aims to entice further research on the future biogeographical impacts of climate change in toxin-producing microalgae species while, at the same time, helping to advise the correct environmental management of coastal habitats and ecosystems. Toxin-producing microalgae present a significant environmental risk for ecosystems and human societies when they reach concentrations that affect other aquatic organisms or human health. Harmful algal blooms (HAB) have been linked to mass wildlife die-offs and human food poisoning episodes, and climate change has the potential to alter the frequency, magnitude, and geographical extent of such events. Thus, a framework of species distribution models (SDMs), employing MaxEnt modeling, was used to project changes in habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2050 and 2100, across four representative concentration pathway scenarios (RCP-2.6, 4.5, 6.0, and 8.5; CMIP5). Despite slightly different responses at the regional level, the global habitat suitability has decreased for all the species, leading to an overall contraction in their tropical and sub-tropical ranges, while considerable expansions are projected in higher latitudes, particularly in the Northern Hemisphere, suggesting poleward distributional shifts. Such trends were exacerbated with increasing RCP severity. Yet, further research is required, with a greater assemblage of environmental predictors and improved occurrence datasets, to gain a more holistic understanding of the potential impacts of climate change on PST-producing species. [ABSTRACT FROM AUTHOR]

Harmful algal blooms are an increasing worldwide threat to the seafood industry and human health as a consequence of the natural production of biotoxins that can accumulate in shellfish. In the Argentine Sea, this has been identified as an issue for the offshore fisheries of Patagonian scallops (Zygochlamys patagonica), leading to potentially harmful effects on consumers. Here we assess spatial and temporal patterns in marine biotoxin concentrations in Patagonian scallops harvested in Argentinian waters between 2012–2017, based on analyses for paralytic shellfish toxins, lipophilic toxins, and amnesic shellfish toxins. There was no evidence for concentrations of lipophilic or amnesic toxins above regulatory acceptance thresholds, with trace concentrations of pectenotoxin 2, azaspiracid 2 and okadaic acid group toxins confirmed. Conversely, paralytic shellfish toxins were quantified in some scallops. Gonyautoxins 1 and 2 dominated the unusual toxin profiles (91%) in terms of saxitoxin equivalents with maximum concentrations reaching 3985 µg STX eq/kg and with changes in profiles linked in part to seasonal changes. Total toxin concentrations were compared between samples of the adductor muscle and whole tissue, with results showing the absence of toxins in the adductor muscle confirming toxin accumulation in the digestive tracts of the scallops and the absence of a human health threat following the processing of scallop adductor meat. These findings highlight that paralytic shellfish toxins with an unusual toxin profile can occur in relatively high concentrations in whole Patagonian scallops in specific regions and during particular time periods, also showing that the processing of scallops on board factory ships to obtain frozen adductor muscle is an effective management process that minimizes the risk of poisonings from final products destined for human consumption. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) are a significant global environmental management challenge, especially with respect to microalgae that produce dangerous natural toxins. Examples of HAB toxin diseases with major global health impact include: ciguatera poisoning, paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), diarrhetic shellfish poisoning (DSP), and neurotoxic (brevetoxin) shellfish poisoning (NSP). Such diseases affect communities globally and contribute to health inequalities within the United States and beyond. Sharing data and lessons learned about the factors determining bloom occurrence and associated exposure to contaminated seafood across locations can reduce public health risks. Knowledge sharing is particularly important as ongoing global environmental changes seem to alter the intensity, location, and timing of toxic HAB events, reducing the reliability of conventional guidance where toxin risks have been endemic and leading to emerging challenges in new settings. Political changes that disrupt membership in knowledge-sharing networks may impede efforts to share scientific expertise and best practices. In this commentary, we stress the importance of community and expert knowledge sharing for reducing HAB risks, both for vulnerable communities in the United States and globally. Considering the impacts of political changes, we note the indirect engagement sometimes required for continued participation in international coordination programs. As an example, we highlight how lessons learned from a Native-led toxin monitoring and testing program (the Southeast Alaska Tribal Ocean Research partnership) can inform programs in other settings. We also describe how international knowledge is mutually valuable for this program in Southeast Alaska. [ABSTRACT FROM AUTHOR]