The physiological adaptations and toxin profiles of the toxic Alexandrium fundyense on the eastern Bering Sea and Chukchi Sea shelves

Abundant cyst distributions of the toxic dinoflagellate Alexandrium fundyense (previous A. tamarense north American clade) were recently observed on the north Chukchi Sea shelf and on the eastern Bering Sea shelf, suggesting that A. fundyense is both highly adapted to the local environments in the high latitude areas and might cause toxin contamination of plankton feeders. However, little is known about the physiological characteristics and toxin profiles of A. fundyense in these areas, which are characterized by low water temperatures, weak sunlight, and more or less permanent ice cover during winter. To clarify the physiological characteristics of A. fundyense, the effects of water temperature and light intensity on the vegetative growth and toxin profiles of this species were examined using A. fundyense strains isolated from one sediment sample collected from each area. Using the same sediments samples, seasonal changes of the cyst germination in different water temperatures were investigated. Vegetative cells grew at temperatures as low as 5°C and survived at 1°C under relatively low light intensity. They also grew at moderate water temperatures (10-15°C). Their cysts could germinate at low temperatures (1°C) and have an endogenous dormancy period from late summer to early spring, and warmer water temperatures (5-15°C) increased germination success. These physiological characteristics suggest that A. fundyense in the Chukchi Sea and eastern Bering Sea is adapted to the environments of high latitude areas. In addition, the results suggest that in the study areas A. fundyense has the potential to germinate and grow when water temperatures increase. Cellular toxin amounts of A. fundyense strains from the eastern Bering Sea and Chukchi Sea were ranged from 7.2 to 38.2 fmol cell^-1. These toxin amounts are comparable with A. fundyense strains isolated from other areas where PSP toxin contamination of bivalves occurs. The dominant toxin of the strains isolated from the Chukchi Sea was saxitoxin, while most A. fundyense strains from the eastern Bering Sea are dominated by the C2 toxin. Toxin profiles similar to those detected in Chukchi Sea have not been reported by any previous research. The dominance of a highly toxic PST variant in Chukchi A. fundyense suggests that presence of the species at low cell concentrations may cause toxin contamination of predators. This study revealed that abundant A. fundyense cysts deposited on the eastern Bering Sea and Chukchi Sea shelves potentially germinate and grow with PSP toxin contents in the local environments. In conclusion, a high risk of PSP occurrences exists on the eastern Bering Sea and Chukchi Sea shelves.

Low dose extended exposure to saxitoxin and its potential neurodevelopmental effects: A review

Saxitoxin (STX) and its analogs, the paralytic shellfish toxins (PSTs), are a group of potent neurotoxins well known for their role in acute paralytic poisoning by preventing the generation of action potentials in neuronal cells. They are found in both marine and freshwater environments globally and although acute exposure from the former has previously received more attention, low dose extended exposure from both sources is possible and to date has not been investigated. Given the known role of cellular electrical activity in neurodevelopment this pattern of exposure may be a significant public health concern. Additionally, the presence of PSTs is likely to be an ongoing and possibly increasing problem in the future. This review examines the neurodevelopmental toxicity of STX, the risk of extended or repeated exposure to doses with neurodevelopmental effects, the potential implications of this exposure and briefly, the steps taken and difficulties faced in preventing exposure.

Case diagnosis and characterization of suspected paralytic shellfish poisoning in Alaska

Clinical cases of paralytic shellfish poisoning (PSP) are common in Alaska, and result from human consumption of shellfish contaminated with saxitoxin (STX) and its analogues. Diagnosis of PSP is presumptive and based on recent ingestion of shellfish and presence of manifestations consistent with symptoms of PSP; diagnosis is confirmed by detection of paralytic shellfish toxins in a clinical specimen or food sample. A clinical diagnostic analytical method using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to evaluate the diagnosis of saxitoxin-induced PSP (STX-PSP) in 11 Alaskan patients using urine specimens collected between June 2010 and November 2011. Concentrations of urinary STX were corrected for creatinine concentrations to account for dilution or concentration of urine from water intake or restriction, respectively. Of the 11 patients with suspected PSP, four patients were confirmed to have STX-PSP by urine testing (24-364ng STX/g creatinine). Five patients had clinical manifestations of PSP though no STX was detected in their urine. Two patients were ruled out for STX-PSP based on non-detected urinary STX and the absence of clinical findings. Results revealed that dysphagia and dysarthria may be stronger indicators of PSP than paresthesia and nausea, which are commonly used to clinically diagnose patients with PSP. PSP can also occur from exposure to a number of STX congeners, such as gonyautoxins, however their presence in urine was not assessed in this investigation. In addition, meal remnants obtained from six presumptive PSP cases were analyzed using the Association of Official Analytical Chemists' mouse bioassay. All six samples tested positive for PSP toxins. In the future, the clinical diagnostic method can be used in conjunction with the mouse bioassay or HPLC-MS/MS to assess the extent of STX-PSP in Alaska where it has been suggested that PSP is underreported.

Liquid Chromatography with a Fluorimetric Detection Method for Analysis of Paralytic Shellfish Toxins and Tetrodotoxin Based on a Porous Graphitic Carbon Column

Paralytic shellfish toxins (PST) traditionally have been analyzed by liquid chromatography with either pre- or post-column derivatization and always with a silica-based stationary phase. This technique resulted in different methods that need more than one run to analyze the toxins. Furthermore, tetrodotoxin (TTX) was recently found in bivalves of northward locations in Europe due to climate change, so it is important to analyze it along with PST because their signs of toxicity are similar in the bioassay. The methods described here detail a new approach to eliminate different runs, by using a new porous graphitic carbon stationary phase. Firstly we describe the separation of 13 PST that belong to different groups, taking into account the side-chains of substituents, in one single run of less than 30 min with good reproducibility. The method was assayed in four shellfish matrices: mussel (Mytillus galloprovincialis), clam (Pecten maximus), scallop (Ruditapes decussatus) and oyster (Ostrea edulis). The results for all of the parameters studied are provided, and the detection limits for the majority of toxins were improved with regard to previous liquid chromatography methods: the lowest values were those for decarbamoyl-gonyautoxin 2 (dcGTX2) and gonyautoxin 2 (GTX2) in mussel (0.0001 mg saxitoxin (STX)·diHCl kg⁻¹ for each toxin), decarbamoyl-saxitoxin (dcSTX) in clam (0.0003 mg STX·diHCl kg⁻¹), N-sulfocarbamoyl-gonyautoxins 2 and 3 (C1 and C2) in scallop (0.0001 mg STX·diHCl kg⁻¹ for each toxin) and dcSTX (0.0003 mg STX·diHCl kg⁻¹ ) in oyster; gonyautoxin 2 (GTX2) showed the highest limit of detection in oyster (0.0366 mg STX·diHCl kg⁻¹). Secondly, we propose a modification of the method for the simultaneous analysis of PST and TTX, with some minor changes in the solvent gradient, although the detection limit for TTX does not allow its use nowadays for regulatory purposes.

Abiotic variables affect STX concentration in a meso-oligotrophic subtropical coastal lake dominated by Cylindrospermopsis raciborskii (Cyanophyceae)

The cyanobacterium Cylindrospermopsis raciborskii is capable of producing toxins including saxitoxin (STX). Few studies have verified the influence of environmental variables on the production of STX and most have only been studied in the laboratory. The goal of this work was to identify the abiotic variables related to STX concentration in situ. The relationship among STX concentration and the physical variables, nutrients and chlorophyll-a (chl-a) concentration was examined in a meso-oligotrophic subtropical coastal lake dominated by C. raciborskii. A generalized linear model was developed, incorporating all variables measured monthly over a 45-month monitoring period. Conductivity and dissolved inorganic nitrogen (DIN) concentration provided the greatest explanatory power for STX concentration in situ. Previous studies suggested that C. raciborskii cells exposed to stress associated with higher ionic concentrations appear to activate the biosynthesis of STX suggesting that STX can elicit changes cell permeability and may contribute to the homeostasis of this organism. An increase of DIN concentration results in a higher concentration of STX which may be related to a reduced metabolic demand, since the uptake of inorganic nitrogen requires less energy than N₂-fixation. Thus, increased DIN can favor the growth of C. raciborskii population or improve cellular homeostasis, both potentially increasing STX concentration in the aquatic system, which was observed through a delayed response pattern. The developed model, while providing only a moderate predictive power, can assist in the understanding of the environmental variables associated with increases in STX concentration, and in monitoring and minimizing the risks of toxic blooms.

Distribution, occurrence and biotoxin composition of the main shellfish toxin producing microalgae within European waters: A comparison of methods of analysis

Harmful algal blooms (HABs) are a natural global phenomena emerging in severity and extent. Incidents have many economic, ecological and human health impacts. Monitoring and providing early warning of toxic HABs are critical for protecting public health. Current monitoring programmes include measuring the number of toxic phytoplankton cells in the water and biotoxin levels in shellfish tissue. As these efforts are demanding and labour intensive, methods which improve the efficiency are essential. This study compares the utilisation of a multitoxin surface plasmon resonance (multitoxin SPR) biosensor with enzyme-linked immunosorbent assay (ELISA) and analytical methods such as high performance liquid chromatography with fluorescence detection (HPLC-FLD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for toxic HAB monitoring efforts in Europe. Seawater samples (n=256) from European waters, collected 2009-2011, were analysed for biotoxins: saxitoxin and analogues, okadaic acid and dinophysistoxins 1/2 (DTX1/DTX2) and domoic acid responsible for paralytic shellfish poisoning (PSP), diarrheic shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP), respectively. Biotoxins were detected mainly in samples from Spain and Ireland. France and Norway appeared to have the lowest number of toxic samples. Both the multitoxin SPR biosensor and the RNA microarray were more sensitive at detecting toxic HABs than standard light microscopy phytoplankton monitoring. Correlations between each of the detection methods were performed with the overall agreement, based on statistical 2×2 comparison tables, between each testing platform ranging between 32% and 74% for all three toxin families illustrating that one individual testing method may not be an ideal solution. An efficient early warning monitoring system for the detection of toxic HABs could therefore be achieved by combining both the multitoxin SPR biosensor and RNA microarray.

Paralytic shellfish toxin production by the dinoflagellate Alexandrium pacificum (Chinhae Bay, Korea) in axenic, nutrient-limited chemostat cultures and nutrient-enriched batch cultures

Blooms of Alexandrium pacificum (formerly Alexandrium tamarense) are common in Chinhae Bay (Korea), presumably linked to anthropogenic eutrophication. Here we examine PSP toxin content and composition in axenic chemostat and batch cultures of A. pacificum using growth conditions that differed according to dilution rate, nutrient limitations, and enrichments. Phosphate (P)-limited cells in chemostat cultures had higher toxin content and a toxin composition that differed from that of nitrogen (N)-limited cells at the highest growth rates. Therefore, toxin composition changes do occur in axenic cultures of A. pacificum following extended growth under steady state conditions. In nutrient-limited batch cultures that received N and P enrichment, the N-enriched cultures showed a more diverse toxin profile than the P-enriched cells; the toxin content of N-enriched cells was lower than in the P-enriched cultures. We infer the following order for the biosynthesis of individual toxins: C1, C2>GTX3>GTX1>neoSTX.

A Rapid Method for the Analysis of Paralytic Shellfish Toxins Utilizing Standard Pressure HPLC: Refinement of AOAC 2005.06

Superficially porous column technologies have previously been shown to provide faster chromatographic analysis of toxin oxidation products when analyzing shellfish for paralytic shellfish toxins. While sub 3 μm fused core columns have facilitated enhanced method performance, including significantly lower analysis times and lower LOD, they were also found to last for only a few hundred injections before pressure increases rendered them unusable with standard HPLC. Recently 5 μm superficially porous columns have become commercially available. In this study, a 5 μm fused core column was used to develop a fast chromatographic method for the analysis of paralytic shellfish toxins, with performance characteristics and column lifetime being assessed. The 5 μm column was found to be able to perform approximately 3000 injections without significant increases in back pressure or reduction in performance. Data generated using the column were found to be equivalent to that determined using current HPLC column technologies for both screening and quantitation methods. Furthermore, an increase in sensitivity for all toxins tested under the routine monitoring program for British waters was observed and the overall run time of the analysis halved. Overall, the 5 μm fused core column provided a significant increase in sample throughput, a reduction in mobile phase consumption, and an increase in method sensitivity.

Determination of Gonyautoxin-4 in Echinoderms and Gastropod Matrices by Conversion to Neosaxitoxin Using 2-Mercaptoethanol and Post-Column Oxidation Liquid Chromatography with Fluorescence Detection

Paralytic Shellfish Toxin blooms are common worldwide, which makes their monitoring crucial in the prevention of poisoning incidents. These toxins can be monitored by a variety of techniques, including mouse bioassay, receptor binding assay, and liquid chromatography with either mass spectrometric or pre- or post-column fluorescence detection. The post-column oxidation liquid chromatography with fluorescence detection method, used routinely in our laboratory, has been shown to be a reliable method for monitoring paralytic shellfish toxins in mussel, scallop, oyster and clam species. However, due to its high sensitivity to naturally fluorescent matrix interferences, when working with unconventional matrices, there may be problems in identifying toxins because of naturally fluorescent interferences that co-elute with the toxin peaks. This can lead to erroneous identification. In this study, in order to overcome this challenge in echinoderm and gastropod matrices, we optimized the conversion of Gonyautoxins 1 and 4 to Neosaxitoxin with 2-mercaptoethanol. We present a new and less time-consuming method with a good recovery (82.2%, RSD 1.1%, n = 3), requiring only a single reaction step.

A tyrosine-containing analog of mu-conotoxin GIIIA as ligand in the receptor binding assay for paralytic shellfish poisons

Development of novel analytical tools to detect marine biotoxins has been warranted in view of the apparent global pervasiveness of algal-derived shellfish poisoning, and the limitations of existing methods. Here, we describe the initial phase in the development and evaluation of a tyrosine-containing analog of μ-conotoxin (μ-CTX) GIIIA as an alternative to saxitoxin (STX) in a receptor binding assay (RBA) for paralytic shellfish poisons. The peptide analog was synthesized and characterized for structure and bioactivity. The major product of oxidation elicited paralytic symptoms in mice at a minimum dose of 1.31 mg kg(-1) (i.p.). Mass spectrometry analysis of the bioactive peptide gave a molecular mass of 2637.52 Da that was close to the predicted value. Iodination via chloramine-T produced non-, mono- and di-iodinated peptides (respectively, NIP, MIP and DIP). Competition assays against (3)H-STX revealed higher Ki and EC50 (P < 0.0001, ANOVA) indicating reduced affinity for the receptor, and limited displacement of receptor-bound STX. However, subsequent use of MIP may extend the application of RBA to detect small changes in toxin levels owing to its likely enhanced displacement by STX. This may be useful in analyzing samples with toxicities near the regulatory limit, or in establishing baseline values in high risk environments.

Environmental effects of modified clay flocculation on Alexandrium tamarense and paralytic shellfish poisoning toxins (PSTs)

Among various mitigation strategies for harmful algal blooms (HABs), the flocculation of algal cells by using modified clay (MC) has been widely applied in the field, particularly in Japan, Korea and China. However, to examine the long-term effects and the environmental safety of this method, we investigated alterations in macronutrients and paralytic shellfish poisoning toxins (PSTs) induced by the application of MC treatment to a toxic bloom, Alexandrium tamarense. The control, algal cells grew in nature condition (A1), was compared to the only MC flocculation (A2) and the MC-sediment co-matrix systems of A. tamarense (A3). The low-dosage of 0.25 g L(-1) MC could efficiently remove >90% of the A. tamarense cells within 3.5h. The mechanisms underlying the effects elicited by MC flocculation on nutrient cycling, PSTs and Chl-a degradation were also discussed. This study demonstrated that MC treatment was able to significantly remove the macronutrients (43-60% TP removal and 17-30% TN removal) and scavenge most of the PSTs from seawater, thereby speeding up the nutrient settling and the transformation and degradation of PSTs (83% decreasing in A2). Simultaneously, the study firstly demonstrated the potential detoxification of PSTs by using MC treatment, from the high toxicity of gonyautoxin 1 and 4 (GTX1 and GTX4) to the lower toxicity decarbamoyl gonyautoxins (dcGTX3) and gonyautoxin 2 (GTX2), particularly within the water-sediment environment during the two month incubation.

Antioxidative responses in zebrafish liver exposed to sublethal doses Aphanizomenon flos-aquae DC-1 aphantoxins

Aphanizomenon flos-aquae secretes paralytic shellfish poisons (PSPs), termed aphantoxins, and endangers environmental and human health via eutrophication of water worldwide. Although the molecular mechanism of neuronal PSP toxicity has been well studied, several issues remain unresolved, notably the in vivo hepatic antioxidative responses to this neurotoxin. Aphantoxins extracted from a natural isolate of A. flos-aquae DC-1 were resolved by high performance liquid chromatography. The primary components were gonyautoxins 1 and 5 and neosaxitoxin. Zebrafish (Danio rerio) were treated intraperitoneally with either 5.3 or 7.61 (low and high doses, respectively) μg saxitoxin (STX) equivalents (eq)/kg of A. flos-aquae DC-1 aphantoxins. Antioxidative responses in zebrafish liver were examined at different timepoints 1-24h post-exposure. Aphantoxin administration significantly enhanced hepatic malondialdehyde (MDA) content 1-12h post-exposure, indicative of oxidative stress and lipid peroxidation. By contrast, levels of reduced glutathione (GSH) in zebrafish liver declined significantly after 3-24h exposure, suggesting that GSH participates in MDA metabolism. A significant upregulation of the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) was observed, suggesting that aphantoxins induce lipid peroxidation in zebrafish liver and are likely to be hepatotoxic. Hepatic levels of MDA and GSH, and of the three enzymes (SOD, CAT, and GPx), therefore provide potential biomarkers for studying environmental exposure to aphantoxins/PSPs from cyanobacterial blooms.

Identification and separation of saxitoxins using hydrophilic interaction liquid chromatography coupled to traveling wave ion mobility-mass spectrometry

The aim of this work was to develop a reliable and efficient analytical method to characterise and differentiate saxitoxin analogues (STX), including sulphated (gonyautoxins, GTX) and non-sulphated analogues. For this purpose, hydrophilic interaction liquid chromatography (HILIC) was used to separate sulphated analogues. We also resorted to ion mobility spectrometry to differentiate the STX analogues because this technique adds a new dimension of separation based on ion gas phase conformation. Positive and negative ionisation modes were used for gonyautoxins while positive ionisation mode was used for non-sulphated analogues. Subsequently, the coupling of these three complementary techniques, HILIC-IM-MS, permitted the separation and identification of STX analogues; isomer differentiation was achieved in HILIC dimension while non-sulphated analogues were separated in the IM-MS dimension. Additional structural characteristics concerning the conformation of STXs could be obtained using IM-MS measurements. Thus, the collision cross sections (CCS) of STXs are reported for the first time in the positive ionisation mode. These experimental CCSs correlated well with the calculated CCS values using the trajectory method.

Molecular phylogeny and PSP toxin profile of the Alexandrium tamarense species complex along the coast of China

To explore the genetic diversity and paralytic shellfish poisoning (PSP) toxin profile of the Alexandrium tamarense species complex along the coast of China, 67 strains of A. tamarense from the China Sea were collected and genetic diversity were analyzed based on the rDNA sequences. In addition, PSP toxin compositions and contents were detected by HPLC. According to the 5.8S rDNA and ITS, and LSU rDNA D1-D2 sequence, A. tamarense in the China Sea comprises at least Group IV and Group I ribotypes. In these Chinese strains, the toxins with the highest concentration in the profile were C1/2, gonyautoxins 1/4 (GTX1/4) and neosaxitoxin (NEO). However, the toxin profiles were atypical and C1/2 toxins were not detected in some strains. No strict correlation was observed between the PSP toxins profile and the geographical distribution.

Multi-detection method for five common microalgal toxins based on the use of microspheres coupled to a flow-cytometry system

Freshwater and brackish microalgal toxins, such as microcystins, cylindrospermopsins, paralytic toxins, anatoxins or other neurotoxins are produced during the overgrowth of certain phytoplankton and benthic cyanobacteria, which includes either prokaryotic or eukaryotic microalgae. Although, further studies are necessary to define the biological role of these toxins, at least some of them are known to be poisonous to humans and wildlife due to their occurrence in these aquatic systems. The World Health Organization (WHO) has established as provisional recommended limit 1μg of microcystin-LR per liter of drinking water. In this work we present a microsphere-based multi-detection method for five classes of freshwater and brackish toxins: microcystin-LR (MC-LR), cylindrospermopsin (CYN), anatoxin-a (ANA-a), saxitoxin (STX) and domoic acid (DA). Five inhibition assays were developed using different binding proteins and microsphere classes coupled to a flow-cytometry Luminex system. Then, assays were combined in one method for the simultaneous detection of the toxins. The IC50's using this method were 1.9±0.1μg L(-1) MC-LR, 1.3±0.1μg L(-1) CYN, 61±4μg L(-1) ANA-a, 5.4±0.4μg L(-1) STX and 4.9±0.9μg L(-1) DA. Lyophilized cyanobacterial culture samples were extracted using a simple procedure and analyzed by the Luminex method and by UPLC-IT-TOF-MS. Similar quantification was obtained by both methods for all toxins except for ANA-a, whereby the estimated content was lower when using UPLC-IT-TOF-MS. Therefore, this newly developed multiplexed detection method provides a rapid, simple, semi-quantitative screening tool for the simultaneous detection of five environmentally important freshwater and brackish toxins, in buffer and cyanobacterial extracts.

Survey of cyanobacterial toxins in Czech water reservoirs--the first observation of neurotoxic saxitoxins

The environmental occurrence and concentrations of cyanobacterial toxins (cyanotoxins) were investigated in the Czech Republic. Concentrations of microcystins (MCs), cylindrospermopsin (CYN) or saxitoxins (STXs) were determined immunochemically by ELISA assays in 30 water samples collected from the surface layers of 19 reservoirs during the summer season of 2010. MCs were detected in 18 reservoirs and 83 % of samples, with median and maximal concentration being 1.5 and 18.6 μg/L, respectively. The high frequency of MC occurrence coincided with prevalence of cyanobacterium Microcystis sp., which was detected in 87 % samples, followed by Dolichospermum (Anabaena) sp. observed in 33 % samples. CYN was detected by ELISA only in one sample at a concentration of 1.2 μg/L. STXs presence was indicated for the first time in Czech water reservoirs when the toxins were found at low concentrations (0.03-0.04 μg/L) in two samples (7 %) collected from two different reservoirs, where STXs co-occurred with MCs and eventually also with CYN. In both STX-positive samples, the phytoplankton community was dominated by Microcystis sp., but Dolichospermum sp. and/or Aphanizomenon sp. were also present as putative producers of STX and/or CYN. Cyanotoxins commonly occurred in Czech water reservoirs, and MCs frequently at concentrations possibly associated with human health risks. MCs were the most prevalent and abundant cyanotoxins, but also other cyanotoxins were detected, though sporadically. Further research and regulatory monitoring of cyanotoxins other than MCs is therefore required.

Evaluation of the MIDTAL microarray chip for monitoring toxic microalgae in the Orkney Islands, U.K

Harmful or nuisance algal blooms can cause economic damage to fisheries and tourism. Additionally, toxins produced by harmful algae and ingested via contaminated shellfish can be potentially fatal to humans. The seas around the Orkney Islands, UK currently hold a number of toxic algal species which cause shellfishery closures in most years. Extensive and costly monitoring programs are carried out to detect harmful microalgae before they reach action levels. However, the ability to distinguish between toxic and non-toxic strains of some algae is not possible using these methods. The microarrays for the detection of toxic algae (MIDTAL) microarray contains rRNA probes for toxic algal species/strains which have been adapted and optimized for microarray use. In order to investigate the use of the chip for monitoring in the Orkney Islands, samples were collected between 2009 and 2011 from Brings Deep, Scapa Flow, Orkney Islands, UK; RNA was extracted and hybridized with generation 2 and 3.1 of the chip. The data were then compared to cell counts performed under light microscopy and in the case of Alexandrium tamarense to qPCR data targeting the saxitoxin gene and the LSU-rRNA gene. A good agreement between cell numbers and microarray signal was found for A. tamarense, Pseudo-nitzschia sp., Dinophysis sp. (r<0.5, for all) in addition to this there the chip successfully detected a large bloom of Karenia mikimotoi (r<0.70) in August and September 2011. Overall, there was good improvement in probe signal between generation 2 and generation 3.1 of the chip with much less variability and more consistent results and better correlation between the probes. The chip performed well for A. tamarense group I signal to cell numbers in calibrations (r>0.9). However, in field samples, this correlation was slightly lower suggesting interactions between all species in the sample may affect signal. Overall, the chip showed it could identify the presence of target species in field samples although some work is needed to improve the quantitative nature of the chip before it would be suitable for monitoring in the Orkney Islands.

The quantitative real-time PCR applications in the monitoring of marine harmful algal bloom (HAB) species

In the last decade, various molecular methods (e.g., fluorescent hybridization assay, sandwich hybridization assay, automatized biosensor detection, real-time PCR assay) have been developed and implemented for accurate and specific identification and estimation of marine toxic microalgal species. This review focuses on the recent quantitative real-time PCR (qrt-PCR) technology developed for the control and monitoring of the most important taxonomic phytoplankton groups producing biotoxins with relevant negative impact on human health, the marine environment, and related economic activities. The high specificity and sensitivity of the qrt-PCR methods determined by the adequate choice of the genomic target gene, nucleic acid purification protocol, quantification through the standard curve, and type of chemical detection method make them highly efficient and therefore applicable to harmful algal bloom phenomena. Recent development of qrt-PCR-based assays using the target gene of toxins, such as saxitoxin compounds, has allowed more precise quantification of toxigenic species (i.e., Alexandrium catenella) abundance. These studies focus only on toxin-producing species in the marine environment. Therefore, qrt-PCR technology seems to offer the advantages of understanding the ecology of harmful algal bloom species and facilitating the management of their outbreaks.

New invertebrate vectors for PST, spirolides and okadaic acid in the North Atlantic

The prevalence of poisoning events due to harmful algal blooms (HABs) has declined during the last two decades through monitoring programs and legislation, implemented mainly for bivalves. However, new toxin vectors and emergent toxins pose a challenge to public health. Several locations on the Portuguese coast were surveyed between 2009 and 2010 for three distinct biotoxin groups [saxitoxin (PST), spirolide (SPX) and okadaic acid (OA)], in 14 benthic species of mollusks and echinoderms. Our main goals were to detect new vectors and unravel the seasonal and geographical patterns of these toxins. PSTs were analyzed by the Lawrence method, SPXs by LC-MS/MS, and OA by LC-MS/MS and UPLC-MS/MS. We report 16 new vectors for these toxins in the North Atlantic. There were differences in toxin contents among species, but no significant geographical or seasonal patterns were found. Our results suggest that legislation should be adjusted to extend the monitoring of marine toxins to a wider range of species besides edible bivalves.

Selection and identification of a DNA aptamer that mimics saxitoxin in antibody binding

In this article, high-affinity single-stranded DNA (ssDNA) aptamer-targeting F(ab')₂ fragments of saxitoxin (STX) antibodies were selected from a random ssDNA library by the SELEX strategy. After 16 rounds of repeated selection, the enriched ssDNA library was sequenced, and all of the sequences were carefully identified by indirect enzyme-linked assay and indirect competitive enzyme-linked assay (icELISA). The candidate aptamers in the above identification were selected for further characterization by icELISA and the equilibrium filtration method. We successfully obtained an aptamer that mimics STX in antibody binding, and a substitute for STX in aptamer form has been developed. Further work is in progress aimed at using this aptamer substitute to replace the STX standard in an antibody-based, nontoxic detection method for field determination of STX in seafood products.

[Application of a fluorescent dye method based on changes in membrane potential in detecting shellfish toxins]

OBJECTIVE

To develop a rapid and sensitive assay for detecting the common sea food toxins including paralytic shellfish poisoning toxin (PST), tetrodotoxin (TTX) and neurotoxic shellfish poisoning toxin (NST) based on their toxicological character.

METHODS

Neuroblastoma cells were incubated with the fluorescent dye bis-oxonol, whose distribution across the membrane was potential-dependent. Changes in membrane potential of the cells induced by gonyautoxins (GTX2,3), brevetoxin (BTX) and TTX were observed respectively, using bis-oxonol.

RESULTS

Within 2 - 200 nmol/L of GTX2,3 or 20 - 600 nmol/L of TTX, veratridine-induced depolarization was shown to be inhibited by GTX2,3 or TTX in dose-dependent manner. Within 15 - 400 ng/ml, there was a dose-dependent relationship between the NSP-induced depolarization and toxin concentration.

CONCLUSION

It was likely to find a rapid, specific, and reliable method with bis-oxonol for detecting GTX2,3, TTX and BTX in sea food.

Algal toxins and reverse osmosis desalination operations: laboratory bench testing and field monitoring of domoic acid, saxitoxin, brevetoxin and okadaic acid

The occurrence and intensity of harmful algal blooms (HABs) have been increasing globally during the past few decades. The impact of these events on seawater desalination facilities has become an important topic in recent years due to enhanced societal interest and reliance on this technology for augmenting world water supplies. A variety of harmful bloom-forming species of microalgae occur in southern California, as well as many other locations throughout the world, and several of these species are known to produce potent neurotoxins. These algal toxins can cause a myriad of human health issues, including death, when ingested via contaminated seafood. This study was designed to investigate the impact that algal toxin presence may have on both the intake and reverse osmosis (RO) desalination process; most importantly, whether or not the naturally occurring algal toxins can pass through the RO membrane and into the desalination product. Bench-scale RO experiments were conducted to explore the potential of extracellular algal toxins contaminating the RO product. Concentrations exceeding maximal values previously reported during natural blooms were used in the laboratory experiments, with treatments comprised of 50 μg/L of domoic acid (DA), 2 μg/L of saxitoxin (STX) and 20 μg/L of brevetoxin (PbTx). None of the algal toxins used in the bench-scale experiments were detectable in the desalinated product water. Monitoring for intracellular and extracellular concentrations of DA, STX, PbTx and okadaic acid (OA) within the intake and desalinated water from a pilot RO desalination plant in El Segundo, CA, was conducted from 2005 to 2009. During the five-year monitoring period, DA and STX were detected sporadically in the intake waters but never in the desalinated water. PbTx and OA were not detected in either the intake or desalinated water. The results of this study demonstrate the potential for HAB toxins to be inducted into coastal RO intake facilities, and the ability of typical RO operations to effectively remove these toxins.

Rapid liquid chromatography for paralytic shellfish toxin analysis using superficially porous chromatography with AOAC Official Method 2005.06

The bioaccumulation of paralytic shellfish toxins in mussels, oysters, cockles, hard clams, razors, and king scallops is monitored in England, Scotland, and Wales by AOAC Official Method 2005.06 LC-with fluorescence detection (FLD). One of the commonly perceived disadvantages of using this method is the long turnaround time and low throughput in a busy laboratory environment. The chromatographic analysis of each sample typically utilizes a 15 min cycle time to achieve toxin oxidation product separation and column equilibration prior to subsequent analysis. A standard RP C18 analytical column, used successfully in recent years, achieves good separation with a long column lifetime. The analysis of a 40 sample qualitative screening batch takes approximately 18 h, including blanks, standards, and other QC samples. The availability of superficially porous column technology has offered the potential to reduce analysis time while retaining column performance on existing hardware. In this study, AOAC Official Method 2005.06 with LC-FLD was transferred to two different commercially available superficially porous columns, and the method performance characteristics were evaluated. Both columns separated all toxins adequately with cycle times less than half that of the existing method. Linearity for each toxin was acceptable up to two times the European maximum permitted limit of 800 microg di-HCl saxitoxin equivalent/kg flesh. LOD and LOQ values were substantially improved for the majority of toxins, with gonyautoxin 1&4 and neosaxitoxin showing up to a two- and fourfold improvement, respectively, depending on the column used. Quantification results obtained from parallel analysis of contaminated samples were acceptable on both columns. Comparative screen results gave a slight increase in the occurrence of contaminated samples, which was attributed to the improved detection limit for most toxins. Issues with rapidly increasing back pressure, however, were identified with both columns, with a limit of around 500 injections. This compares to the >3000 cycles routinely obtained with the standard RP-C18 HPLC columns currently in use. Overall, the gain achieved with these columns through shorter analysis time and improved analytical sensitivity is potentially of benefit in a high-throughput environment. For the routine high-throughput screening of shellfish samples, however, an improved column lifetime is desirable.

Toxin levels and profiles in microalgae from the north-Western Adriatic Sea--15 years of studies on cultured species

The Northern Adriatic Sea is the area of the Mediterranean Sea where eutrophication and episodes related to harmful algae have occurred most frequently since the 1970s. In this area, which is highly exploited for mollusk farming, the first occurrence of human intoxication due to shellfish consumption occurred in 1989, nearly 10 years later than other countries in Europe and worldwide that had faced similar problems. Until 1997, Adriatic mollusks had been found to be contaminated mostly by diarrhetic shellfish poisoning toxins (i.e., okadaic acid and dinophysistoxins) that, along with paralytic shellfish poisoning toxins (i.e., saxitoxins), constitute the most common marine biotoxins. Only once, in 1994, a toxic outbreak was related to the occurrence of paralytic shellfish poisoning toxins in the Adriatic coastal waters. Moreover, in the past 15 years, the Adriatic Sea has been characterized by the presence of toxic or potentially toxic algae, not highly widespread outside Europe, such as species producing yessotoxins (i.e., Protoceratium reticulatum, Gonyaulax spinifera and Lingulodinium polyedrum), recurrent blooms of the potentially ichthyotoxic species Fibrocapsa japonica and, recently, by blooms of palytoxin-like producing species of the Ostreopsis genus. This review is aimed at integrating monitoring data on toxin spectra and levels in mussels farmed along the coast of the Emilia-Romagna region with laboratory studies performed on the species involved in the production of those toxins; toxicity studies on toxic or potentially toxic species that have recently appeared in this area are also reviewed. Overall, reviewed data are related to: (i) the yessotoxins producing species P. reticulatum, G. spinifera and L. polyedrum, highlighting genetic and toxic characteristics; (ii) Adriatic strains of Alexandrium minutum, Alexandrium ostenfeldii and Prorocentrum lima whose toxic profiles are compared with those of strains of different geographic origins; (iii) F. japonica and Ostreopsis cf. ovata toxicity. Moreover, new data concerning domoic acid production by a Pseudo-nitzschia multistriata strain, toxicity investigations on a Prorocentrum cf. levis, and on presumably ichthyotoxic species, Heterosigma akashiwo and Chattonella cf. subsalsa, are also reported.

A coagulation-powdered activated carbon-ultrafiltration--multiple barrier approach for removing toxins from two Australian cyanobacterial blooms

Cyanobacteria are a major problem for the world wide water industry as they can produce metabolites toxic to humans in addition to taste and odour compounds that make drinking water aesthetically displeasing. Removal of cyanobacterial toxins from drinking water is important to avoid serious illness in consumers. This objective can be confidently achieved through the application of the multiple barrier approach to drinking water quality and safety. In this study the use of a multiple barrier approach incorporating coagulation, powdered activated carbon (PAC) and ultrafiltration (UF) was investigated for the removal of intracellular and extracellular cyanobacterial toxins from two naturally occurring blooms in South Australia. Also investigated was the impact of these treatments on the UF flux. In this multibarrier approach, coagulation was used to remove the cells and thus the intracellular toxin while PAC was used for extracellular toxin adsorption and finally the UF was used for floc, PAC and cell removal. Cyanobacterial cells were completely removed using the UF membrane alone and when used in conjunction with coagulation. Extracellular toxins were removed to varying degrees by PAC addition. UF flux deteriorated dramatically during a trial with a very high cell concentration; however, the flux was improved by coagulation and PAC addition.