Domoic Acid

Domoic acid (DA) is a neurotoxin produced by the harmful algae Pseudo-nitzschia that has been directly linked to mass stranding events of the California Sea Lion (CSL). The purpose of this paper is to review the anthropogenic influence on the production of this neurotoxin and examine how human activities are impacting this marine mammal species. A comprehensive and interdisciplinary literature review was conducted to evaluate the future sustainability of the CSL population. It was found that while Pseudo-nitzschia bloom developments are vulnerable to anthropogenic influences, the incontestable existence of natural contributing factors adds a certain complexity to the determination of causalities and the development of solutions. Strong evidence exists to show that DA can cause major and irreversible neurological damage in CSLs. Rehabilitation of DA-impacted CSLs is a polarizing issue in the U.S. and presents interesting implications for sustainable development. While the CSL populat...

This thesis is dedicated to my late Uncle Neil, whose relentless zest for life, unstoppable thirst for knowledge, and constant yearning for adventure inspired me to further my education and study in Sweden. "Better to light one small candle than curse the darkness" -Chinese Proverb Lastly, a special thanks goes out to Gai-lan, a wonderful and charming harbour seal who was the very first marine mammal that I was involved in the rescue, rehabilitation, and release of.

Preliminary results on the application of capillary electrochromatography to the analysis of domoic acid* The feasibility of using capillary electrochromatography (CEC) with photodiode array detection for the analysis of domoic acid (DA), responsible for Amnesic Shellfish Poisoning (ASP), is presented. Factors influencing the separation performance have been investigated. Using a reverse phase column (C18) and a mobile phase consisting of 5 mM phosphate buffer (pH 2.5) -acetonitrile (40 : 60) with an applied voltage of 7 kV, the separation of domoic acid from other compounds in spiked uncontaminated razor clams was accomplished. These preliminary results show the promising potential of the technique as an alternative to HPLC or capillary electrophoresis (CE) for the analysis of such compounds in biological samples.

Domoic acid (DA) is a neurotoxic amino acid that is responsible for the human toxic syndrome, amnesic shellfish poisoning (ASP). A new rapid, sensitive liquid chromatographic (LC) method has been developed for the determination of DA in various marine samples. DA in marine biological materials was derivatised with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and analysed using isocratic reversed-phase LC with fluorimetric detection. The calibration, based on standard DA 2 solutions, was linear in the range 0.04-2 mg / ml (r 50.998) and the detection limit (3:1, signal / noise) was better than 1 ng / ml. Using the certified reference material (MUS-1B), recoveries of DA from shellfish tissue were .95% (n55). When a strong anion exchange SPE cartridge was used for sample clean-up the detection limit was 6 ng DA / g mussel tissue. Good reproducibility was achieved with RSD values ranging from 3% for 8 mg DA/g (n55), to 5% for 0.04 mg DA/g (n55). This new method was successfully applied to the determination of DA in naturally contaminated shellfish and in marine phytoplankton cultures of Pseudonitzschia sp.

Human exposure to naturally occurring marine toxins has been associated with a range of neurobehavioral abnormalities. The toxins are produced by harmful algal blooms (HABs) and are typically contracted through seafood consumption. The primary target of many of the HAB toxins is the neurologic system, and the neurobehavioral symptoms associated with the HAB illnesses have influenced public health policy. The HAB-related illnesses most frequently linked to neuropsychological disturbance are Amnesic Shellfish Poisoning, Ciguatera Fish Poisoning, and Possible Estuarine Associated Syndrome, which is associated with exposure to thePfiesteria piscicidaorganism. Although the neurophysiologic mechanisms underlying many of the HAB illnesses have been well delineated, the literature examining the neuropsychological impairments is unclear and needs to be defined. This review is intended to introduce an emerging area of study linking HAB illnesses with neuropsychological changes. (JINS, 2005,11...

The physiological effects of domoic acid on marine invertebrates which are known to accumulate this neurotoxin have not been investigated previously. Changes in haemolymph pH, PCO,, and PO* were measured in Crassostrea gigas and Mytilus californianus when exposed continuously to the domoic acid producing diatom, Pseudonitzschia pungens f. multiseries, for 48 h followed by a 120 h clearance period. A general stress response by C. gigas was characterized by a respiratory acidosis from shell closure 4-8 h after introduction of the algae. Haemolymph pH in the oyster returned to control levels after 36 h exposure and although hypoxic conditions persisted during 48 h exposure PO, levels returned to normal only after 24 h of clearance. Substantial hypercapnia and elevated haemolymph bicarbonate occurred after 8 h exposure which was rectified during the remaining period of exposure. Body burden of domoic acid was greatest in the oyster after 4 h of exposure. At 120 h of continuous clearance the gill, muscle, and soft tissue still revealed detectable levels of domoic acid. M. californianus exhibited no significant change in haemolymph pH on exposure to the alga although a slight alkalosis occurred, which is associated normally with increased filtration (feeding) and gas exchange. Haemolymph PCO, and PO, were within the range of established control values throughout the experiment. Domoic acid was assimilated to the highest level in gill tissue and no detectable concentration of toxin was observed in any tissue after 120 h of clearance.

Haemocyte changes in the Pacific oyster, Crassostrea gigas, caused by exposure to domoic acid in the diatom Pseudonitzschia pungens f. multiseries. Toxicon 33, 347-353, 1995.--The physiological effects of domoic acid on the immune system of marine invertebrates, which are known to accumulate this neurotoxin, have not been investigated previously. Changes in the number and relative phagocytic activity of circulating haemocytes in Crassostrea gigas exposed to domoic acid in the diatom Pseudonitzschia pungens f. multiseries for 48 hr, followed by clearance for 240 hr, were investigated using chemiluminescence. An initial stress response to the toxin assimilation was characterized by a marked increase in number and activity of haemocytes with 4 hr of exposure to the algae. Although the toxin level in the oyster increased during the 48 hr exposure, both number and activity of haemocytes declined from the 4 hr peak value,; to those significantly lower than control values after 24 hr clearance. This suppression in number and activity of circulating haemocytes following the initial toxin response was rectified only after 48 hr clearance, when domoic acid levels in the oyster tissue had declined to trace levels, allowing blood cells to regain their normal characteristics.

The king scallop, Pecten maximus (L.), fishery is a valuable economic resource in the UK, and is reliant on supplying premium "roe-on" processed scallops to the continental market. A considerable degree of variability is observed in domoic acid (DA) levels among individual P. maximus and their body components, which complicates the management of the fishery during amnesic shellfish poisoning (ASP) events. This study examined the impact of professional processing and three differing laboratory preparation techniques on final gonadal DA levels. DA analysis was conducted using a LC-MS/MS procedure. The results demonstrate that different methods of preparation can significantly alter gonadal toxicities in scallops from the same site, and the extent to which DA within the digestive loop, which passes through the gonad, contributes to total gonadal DA. Mean gonadal toxicity attributed to the digestive loop contents was estimated at 4.7-24.7 g DA g -1 . Despite large individual variations in toxin levels; in scallops with elevated gonadal toxicities resulting from higher digestive loop content toxicity, the effect of flushing out the contents of the digestive loop significantly reduced the DA content of the tissue and lowered the frequency of individuals harbouring levels above the 20 g DA g -1 statutory safety limit. Removal of the digestive loop contents can potentially result in an 87% decrease in gonadal DA burden. Furthermore, the method applied by professional processors effectively removed the contents of the digestive loop and reduced gonadal DA to levels comparable with the laboratory techniques. Deliberate contamination with scallop mucus did not increase gonadal DA levels. The extent of toxin variation resulting from differing gonad preparations demonstrates the need to standardize scallop tissue preparation techniques during ASP events. Consequently, detailed protocols aimed at minimizing the contamination of edible components should be developed and adhered to by both processing facilities and monitoring bodies.

Okadaic Acid (OA) the major diarrheic shellfish poisoning (DSP) toxin is known as a tumor promoter and seems likely implicated in the genesis of digestive cancer. Little is known regarding genotoxicity and carcinogenicity of Domoic Acid (DA), the major Amnesic Shellfish Poisoning (ASP) toxin. Both OA and DA occur in seafood and are of human health concerns. Micronuclei (MN) arise from abnormalities in nuclear division during mitosis due to a failure of the mitotic spindle or by complex chromosomal configurations that pose problems during anaphase. In order to evaluate the ability of okadaic acid (OA) and domoic acid (DA) to induce DNA damage we performed the micronucleus assay using the Caco-2 cell line. To discriminate between a clastogenic or aneugenic effect of OA and DA, the micronucleus assay was conducted by cytokinesis-block micronucleus assay using cytochalasin B with Giemsa staining and/or acridine orange staining, in parallel to fluorescence in situ hybridization (FISH) using a concentrated human pan-centromeric chromosome paint probe. Our results showed that OA and DA significantly increased the frequency of MN in Caco-2 cells. The MN caused by OA are found in mononucleated cells and binucleated cells, whereas those caused by DA are mainly in binucleated cells. The results of FISH analysis showed that OA induced centromere-positive micronuclei and DA increased the percentage of MN without a centromeric signal. In conclusion, both OA and DA bear mutagenic potential as revealed in Caco-2 cells by induction of MN formation. Moreover, OA induced whole chromosome loss suggesting a specific aneugenic potential, whereas DA seems simply clastogenic. At present, one cannot rule out possible DNA damage of intestinal cells if concentrations studied are reached in vivo, since this may happen with concentrations of toxins just below regulatory limits in case of frequent consumption of contaminated shell fishes.

Okadaic Acid (OA) the major diarrheic shellfish poisoning (DSP) toxin is known as a tumor promoter and seems likely implicated in the genesis of digestive cancer. Little is known regarding genotoxicity and carcinogenicity of Domoic Acid (DA), the major Amnesic Shellfish Poisoning (ASP) toxin. Both OA and DA occur in seafood and are of human health concerns. Micronuclei (MN) arise from abnormalities in nuclear division during mitosis due to a failure of the mitotic spindle or by complex chromosomal configurations that pose problems during anaphase. In order to evaluate the ability of okadaic acid (OA) and domoic acid (DA) to induce DNA damage we performed the micronucleus assay using the Caco-2 cell line. To discriminate between a clastogenic or aneugenic effect of OA and DA, the micronucleus assay was conducted by cytokinesis-block micronucleus assay using cytochalasin B with Giemsa staining and/or acridine orange staining, in parallel to fluorescence in situ hybridization (FISH) using a concentrated human pan-centromeric chromosome paint probe. Our results showed that OA and DA significantly increased the frequency of MN in Caco-2 cells. The MN caused by OA are found in mononucleated cells and binucleated cells, whereas those caused by DA are mainly in binucleated cells. The results of FISH analysis showed that OA induced centromere-positive micronuclei and DA increased the percentage of MN without a centromeric signal. In conclusion, both OA and DA bear mutagenic potential as revealed in Caco-2 cells by induction of MN formation. Moreover, OA induced whole chromosome loss suggesting a specific aneugenic potential, whereas DA seems simply clastogenic. At present, one cannot rule out possible DNA damage of intestinal cells if concentrations studied are reached in vivo, since this may happen with concentrations of toxins just below regulatory limits in case of frequent consumption of contaminated shell fishes.

Domoic acid ([2S-[2α,3β,4β(1Z,3E,5S*)]]-2-carboxy-4-(5-carboxy-1-methyl-1,3-hexadienyl)-3-pyrrolidineacetic acid, DA), a harmful algal toxin produced by several microorganisms genus involved in red tides, was tested for degradation in de-ionized and synthetic sea water using Fenton and Fenton-like advanced oxidation processes (AOPs). Four different AOPs-Fenton, photo-Fenton, cobalt/peroxymonosulfate and cobalt/peroxymonosulfate/ UV-were tested. Cobalt/PMS/UV demonstrated the highest initial reaction rate when compared with the other oxidation processes tested. Results obtained from tests performed in synthetic sea water were similar for the case of Co/PMS/UV process whereas important decrease in degradation reaction rate was observed for photo-Fenton reaction probably due to the formation of chlorine-Fe 2+ or sulfate-Fe 2+ complexes.

Over the last several decades, countries throughout the world have experienced an escalating and worrisome trend in the incidence of harmful algal blooms (HABs). A concern is that highly potent algal toxins might be retained in the treated water, posing a threat to human health. Seawater contaminated with saxitoxins, domoic acid, okadaic acid, and brevetoxins was desalinated using small (<100 mL capacity) reverse osmosis and distillation equipment. Analyses of desalinated water samples indicated efficient removal of the four toxins to greater than 99%, except brevetoxins for which some carryover was observed during distillation. Hypochlorite concentrations of 4 ppm or higher were sufficient to react with all of the saxitoxins, domoic acid and okadaic acid in the samples that contained initial toxin concentrations up to 1,250 ng.mL -1 . Brevetoxins appeared to be unaffected in experiments in which the toxins were exposed to up to 30 ppm hypochlorite in seawater at 35 °C for 60 min. These results and their implications in terms of desalination plant design and operation are discussed. LC Liquid chromatography MS Mass spectrometry ELISA Enzyme-linked immunosorbent assay STX Saxitoxin PSP Paralytic shellfish poisoning ASP Amnesic shellfish poisoning DSP Diarrhetic shellfish poisoning NSP Neurotoxic shellfish poisoning RO Reverse osmosis MSF Multistage flash evaporation

Over the last several decades, countries throughout the world have experienced an escalating and worrisome trend in the incidence of harmful algal blooms (HABs). A concern is that highly potent algal toxins might be retained in the treated water, posing a threat to human health. Seawater contaminated with saxitoxins, domoic acid, okadaic acid, and brevetoxins was desalinated using small (<100 mL capacity) reverse osmosis and distillation equipment. Analyses of desalinated water samples indicated efficient removal of the four toxins to greater than 99%, except brevetoxins for which some carryover was observed during distillation. Hypochlorite concentrations of 4 ppm or higher were sufficient to react with all of the saxitoxins, domoic acid and okadaic acid in the samples that contained initial toxin concentrations up to 1,250 ng.mL -1 . Brevetoxins appeared to be unaffected in experiments in which the toxins were exposed to up to 30 ppm hypochlorite in seawater at 35 °C for 60 min. These results and their implications in terms of desalination plant design and operation are discussed. LC Liquid chromatography MS Mass spectrometry ELISA Enzyme-linked immunosorbent assay STX Saxitoxin PSP Paralytic shellfish poisoning ASP Amnesic shellfish poisoning DSP Diarrhetic shellfish poisoning NSP Neurotoxic shellfish poisoning RO Reverse osmosis MSF Multistage flash evaporation

In order to obtain more detailed information on the distribution of domoic acid-producing Nitzschia in Asian waters, Nitzschia-like diatoms were isolated primarily from the Philippines and established in culture for analysis by HPLC with fluorescence detection. Out of 58 isolates, 35 Nitzschia-like diatoms from the estuary areas of San Pedro Bay, Tacloban City and Manila Bay showed significant levels of domoic acid production (1.3-5.6 pg/cell). These were identified as Nitzschia navis-varingica. Two isolates from the same locality did not produce domoic acid. Of the 21 isolates from Bulacan Estuary, Manila Bay, none produced domoic acid. They did, however, produce two substances that seemed to be domoic acid derivatives. One of the strains was mass cultured and the substances were extracted, purified and analyzed by LC-MS/MS, proton and 13 C NMR, and UV spectra. The produced substances were determined as isodomoic acids A and B. This is the first report of a diatom that produces isodomoic acids A and B as major toxin components.

Copepod Behavior in "Cryptic Blooms" of Toxic Algae A.C. TRUE, D.R. WEBSTER, M.J. WEISSBURG, J. YEN, Georgia Tech -Copepods, Acartia tonsa and Temora longicornis, were exposed to thin layers of exudates from the toxic dinoflagellate Karenia brevis (1 -10,000 cells/mL) (i.e. models of "cryptic blooms" of toxic phytoplankton). Planar laser-induced fluorescence (PLIF) was used to quantify the spatiotemporal structure of the layer allowing for correlation of behavioral responses with toxin levels. Both species explicitly avoided the exudate layer and the vicinity of the layer. Measures of path kinematics (swimming speed, turn frequency) by location (in-layer vs. out-of-layer) and exposure (precontact vs. post-contact) revealed some similarities, but also significant differences, in trends for each species. A. tonsa significantly increases swimming speed and swimming speed variability in the exudate layer and post-contact, whereas T. longicornis slightly increases both in-layer and slightly reduces both post-contact. Both species increase turn frequency in-layer and post-contact with increasing K. brevis exudate concentration. Path fracticality indicates that A. tonsa trajectories became more diffuse/sinuous and T. longicornis trajectories became more linear/ballistic (trending effects). Regression analyses revealed that the rate of change of behavior with increasing exudate concentration for A. tonsa was thrice to fifty times that of T. longicornis. Toxic K. brevis can essentially eliminate top-down grazer control,another sinister means by which it gains a competitive advantage over the local phytoplankton taxa.

Marine toxins, such as saxitoxin and domoic acid are associated with algae blooms and can bioaccumulate in shell fish which present both health and economic concerns. The ability to detect the presence of toxin is paramount for the administration of the correct supportive care in case of intoxication; environmental monitoring to detect the presence of toxin is also important for prevention of intoxication. Immunoassays are one tool that has successfully been applied to the detection of marine toxins. Herein, we had the variable regions of two saxitoxin binding monoclonal antibodies sequenced and used the information to produce recombinant constructs that consist of linked heavy and light variable domains that make up the binding domains of the antibodies (scFv). Recombinantly produced binding elements such as scFv provide an alternative to traditional antibodies and serve to "preserve" monoclonal antibodies as they can be easily recreated from their sequence data. In this paper, we combined the anti-saxitoxin scFv developed here with a previously developed anti-domoic acid scFv and demonstrated their utility in a microsphere-based competitive immunoassay format. In addition to detection in buffer, we demonstrated equivalent sensitivity in oyster and scallop matrices. The potential for multiplexed detection using scFvs in this immunoassay format is demonstrated.

Marine toxins, such as saxitoxin and domoic acid are associated with algae blooms and can bioaccumulate in shell fish which present both health and economic concerns. The ability to detect the presence of toxin is paramount for the administration of the correct supportive care in case of intoxication; environmental monitoring to detect the presence of toxin is also important for prevention of intoxication. Immunoassays are one tool that has successfully been applied to the detection of marine toxins. Herein, we had the variable regions of two saxitoxin binding monoclonal antibodies sequenced and used the information to produce recombinant constructs that consist of linked heavy and light variable domains that make up the binding domains of the antibodies (scFv). Recombinantly produced binding elements such as scFv provide an alternative to traditional antibodies and serve to &quot;preserve&quot; monoclonal antibodies as they can be easily recreated from their sequence data. In this ...

A single strain of Pseudo-nitzschia multiseries was grown axenically and in parallel cultures to which selected bacterial species isolated previously from P. multiseries cultures were added (non-axenic culture), an Alteromonas sp. (a producer of gluconic acid/gluconolactone when grown with glucose) and a Moraxella sp. (a non-producer of gluconic acid/gluconolactone). When gluconic acid/gluconolactone was added to the axenic culture the production of domoic acid was increased to double that produced by the non-axenic culture. The effect of the gluconic acid/gluconolactone on domoic acid production was concentration dependent and could be offset completely by the addition of glutamic acid or proline to cultures containing gluconic acid/gluconolactone. Domoic acid, depending upon culture conditions, was partitioned in varying percentages between the diatom cells and the culture filtrates. It is suggested that the enhancement of the algal production of domoic acid in the presence of specific bacteria could be influenced by production of gluconic acid/gluconolactone by bacteria; this effect may be a direct result of the antagonistic effect of the powerful sequestering properties of gluconic acid which, through tying up nutrients, induces the diatom to produce a counter chelating agent, domoic acid.

EFSA was asked by the European Commission to provide information on levels of lipophilic shellfish toxins in whole scallops that would ensure levels in edible parts below the regulatory limits after shucking, i.e. removal of non-edible parts. This should include the okadaic acid (OA), the azaspiracid (AZA) and the yessotoxin (YTX) groups, and five species of scallops. In addition, EFSA was asked to recommend the number of scallops in an analytical sample. To address these questions, EFSA received suitable data on the three toxin groups in two scallop species, Aequipecten opercularis and Pecten maximus, i.e. data on individual and pooled samples of edible and non-edible parts from contamination incidents. The majority of the concentration levels were below limit of quantification (LOQ)/limit of detection (LOD), especially in adductor muscle but also in gonads. Shucking in most cases resulted in a strong decrease in the toxin levels. For Pecten maximus, statistical analysis showed that levels in whole scallops should not exceed 256 lg OA eq/kg or 217 lg AZA1 eq/kg to ensure that levels in gonads are below the regulatory limits of 160 lg OA or AZA1 eq/kg with 99% certainty. Such an analysis was not possible for yessotoxins or any toxin in Aequipecten opercularis and an assessment could only be based on upper bound levels. To ensure a 95% correct prediction on whether the level in scallops in an area or lot is correctly predicted to be compliant/non-compliant, it was shown that 10 scallops per sample would be sufficient to predict with 95% certainty if levels of OA-group toxins in the area/lot were 25% below or above the regulatory limit. However, to predict with a 95% certainty for levels between 140 and 180 lg OA eq/kg, a pooled sample of more than 30 scallops would have to be tested.

Amnesic shellfish poisoning (ASP) is a potentially lethal human toxic syndrome which is caused by domoic acid (DA) that originates in marine phytoplankton belonging to the Pseudonitzschia genus. A confirmatory and sensitive procedure has been developed and validated for the determination of DA in shellfish. The proposed method includes pressurised liquid extraction (PLE) with methanol/acetone (9:1), florisil ® cleanup purification inside the PLE extraction cell and detection by liquid chromatography (LC) coupled to electrospray ionization in positive mode tandem mass spectrometry (ESI-MS-MS). Comparison of ionization sources (ESI, atmospheric pressure ionization (APCI) atmospheric pressure photoionization (APPI) and combined APCI/APPI) were carried out in order to improve the analytical signal. The main parameters affecting the performance of the different ionization sources and PLE parameters were previously optimised using statistical design of experiments (DOE). Linear calibrations were obtained using mussel tissue extracts 0.05-5 g DA/ml (R 2 > 0.999). The limits of detection (LOD) and quantitation (LOQ) of the method were 0.2 and 0.5 g/g respectively and recoveries ranged from 81 to 95%. This method was successfully applied to determine DA levels in 46 shellfish samples collected from Valencian (Spain) supermarkets, showing high sample throughput.

Domoic acid (DA) is a glutaminergic excitatory neurotoxin that causes morbidity and mortality of California sea lions (Zalophus californianus; CSL) and other marine mammals due to a suite of effects mostly on the nervous and cardiac systems. Between 1998 and 2019, 11,737 live-stranded CSL were admitted to The Marine Mammal Center (TMMC; Sausalito, CA, USA), over 2,000 of which were intoxicated by DA. A plethora of clinical research has been performed over the past 20 years to characterize the range of toxic effects of DA exposure on CSLs, generating the largest dataset on the effects of natural exposure to this toxin in wildlife. Here we review published methods for diagnosing DA intoxication, clinical presentation and treatment of DA-intoxicated CSL, and present a practical, reproducible scoring system called the neuroscore (NS) to help assess whether a DA-affected CSL is fit for release to the wild following rehabilitation. The largest proportion of DA-intoxicated CSL were adult f...

BACKGROUND Domoic acid (DA) is a naturally occurring neurotoxin harmful to marine animals and humans. California sea lions exposed to DA in prey during algal blooms along the Pacific coast exhibit significant neurological symptoms, including epilepsy with hippocampal atrophy. OBSERVATIONS Here the authors describe a xenotransplantation procedure to deliver interneuron progenitor cells into the damaged hippocampus of an epileptic sea lion with suspected DA toxicosis. The sea lion has had no evidence of seizures after the procedure, and clinical measures of well-being, including weight and feeding habits, have stabilized. LESSONS These preliminary results suggest xenotransplantation has improved the quality of life for this animal and holds tremendous therapeutic promise.

The productive but highly exposed coastline of the southern Benguela eastern boundary upwelling system offers limited natural environment for aquaculture. Saldanha Bay located on the west coast of South Africa is one of the few embayments on the coastline that provides a productive and relatively sheltered environment suitable for the cultivation of shellfish. Consequently, bivalve culture in South Africa is centered in Saldanha Bay and is presently targeted for expansion. Pseudo-nitzschia blooms including toxin-producing species are shown to contribute significantly to the phytoplankton of Saldanha Bay specifically in spring and summer. Their dominance at this time of the year, when upwelling is strongest, fits the ecological profile of Pseudo-nitzschia occurring during periods of high turbulence and nutrients. Multiple Pseudo-nitzschia blooms were sampled under varying environmental conditions and the strength of the relationship between Pseudo-nitzschia cell abundance and particulate domoic acid (pDA) content, reflecting bloom toxicity, varied greatly. This variability is the result of the combined influence of species and strain composition of the Pseudo-nitzschia assemblage and the effect of environmental conditions on toxin production. Elevated levels of pDA were associated with higher concentrations of cells of the P. seriata complex differentiated by frustule width (>3 µm). P. australis was identified as a toxin-producing species and a prominent member of the P. seriata complex. Low DA levels in shellfish in Saldanha Bay are considered a function of low cellular domoic acid (cDA). Silicate limitation has emerged as an important factor inducing DA production in Pseudo-nitzschia species. The high ratio of silicate to nitrate in Saldanha Bay provides a plausible explanation for the low toxin content of Pseudo-nitzschia blooms in the bay and the consequent low risk posed by these blooms to the aquaculture sector.

Harmful algal blooms (HABs), varying in intensity and causative species, have historically occurred throughout the Chesapeake Bay, U.S.; however, phycotoxin data are sparse. The spatiotemporal distribution of phycotoxins was investigated using solid-phase adsorption toxin tracking (SPATT) across 12 shallow, nearshore sites within the lower Chesapeake Bay and Virginia's coastal bays over one year (2017)(2018). Eight toxins, azaspiracid-1 (AZA1), azaspiracid-2 (AZA2), microcystin-LR (MC-LR), domoic acid (DA), okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), and goniodomin A (GDA) were detected in SPATT extracts. Temporally, phycotoxins were always present in the region, with at least one phycotoxin group (i.e., consisting of OA and DTX1) detected at every time point. Co-occurrence of phycotoxins was also common; two or more toxin groups were observed in 76% of the samples analyzed. Toxin maximums: 0.03 ng AZA2/g resin/day, 0.25 ng DA/ g resin/day, 15 ng DTX1/g resin/day, 61 ng OA/g resin/day, 72 ng PTX2/g resin/day, and 102,050 ng GDA/g resin/day were seasonal, with peaks occurring in summer and fall. Spatially, the southern tributary and coastal bay regions harbored the highest amount of total phycotoxins on SPATT over the year, and the former contained the greatest diversity of phycotoxins. The novel detection of AZAs in the region, before a causative species has been identified, supports the use of SPATT as an explorative tool in respect to emerging threats. The lack of karlotoxin in SPATT extracts, but detection of Karlodinium veneficum by microscopy, however, emphasizes that this tool should be considered complementary to, but not a replacement for, more traditional HAB management and monitoring methods.

This paper shows the results of an intralaboratory validation of a fast method for the determination of lipophilic shellfish toxins working under acidic conditions using ultra-high performance LC (UHPLC) with MS/MS. Fourteen lipophilic marine toxins and domoic acid were acquired with fast polarity switching.Whereas azaspiracids (AZAs), pecenotoxins, 13-desmethyl spirolide C (SPX1), and gymnodimine were analyzed in the positive mode, yessotoxins (YTXs) were measured in negative mode. The okadaic acid (OA) group compounds were analyzed in both positive and negativeionization modes, and the accuracy of the results for both were compared. When using dynamic multiple reaction monitoring (MRM) in fast polarity switching, LODs were lower and reproducibility and linearity were better compared to static MRM. The UHPLC separation allowed for higher sample throughput in routineuse. Compared to the previously used HPLC/MS/MS method, LODs were improved up to a factor of 10 in mussel extract. Mat...

Domoic acid (DOM) is known to cause hippocampal neuronal damage and produces amnesic effects. We examined synaptic plasticity changes induced by DOM exposure in rat hippocampal CA1 region. Brief bath application of DOM to hippocampal slices produces a chemical form of long-term potentiation (LTP) of CA1 field synaptic potentials. The potentiation cannot be blocked by NMDA receptor antagonist MK-801 but can be blocked by the calcium-calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-62 or cAMP-dependent protein kinase (PKA) inhibitor H-89. DOM-potentiated slices show decreased autophosphorylated CaMKII (p-Thr286), an effect that is also dependent on the activity of CaMKII and PKA. Increased phosphorylation of a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit GluR1 (p-Ser831) was seen in DOM-potentiated slices. Therefore, aberrant regulation of CaMKII and GluR1 phosphorylation occurs after DOM application. In addition, tetanus-induced LTP as well as the increase of phosphorylation of CaMKII (p-Thr286) were reduced in DOM-potentiated slices. Compared with brief exposure, slices recovering from prolonged exposure did not show potentiation or altered levels of CaMKII (p-Thr286) or GluR (p-Ser831). However, decreased phosphorylation of GluR1 at Ser845 was seen. These results describe a new chemical form of LTP and uncover novel molecular changes induced by DOM. The observed impairment of tetanus LTP and misregulation of CaMKII and GluR1 phosphorylation may partially account for DOM neurotoxicity and underlie the molecular basis for DOM-induced memory deficit.

The increasing occurrence of poisoning accidents in marine animals caused by the amnesic shellfish toxin, domoic acid (DOM), necessitates a better understanding of the factors contributing to DOM neurotoxicity. Here we evaluated the contribution and temporal involvement of NMDA, non-NMDA-and metabotropic-type glutamate receptors (GluRs) in DOM-induced neuronal death using rat primary mixed cortical cultures. Coapplication of antagonists for AMPA/kainate-(NBQX) and NMDA-type GluRs (D-AP5) but not for metabotropic GluRs reduced DOM toxicity induced by either of three EC 50 dose/ duration exposure paradigms. Maximal protection offered by D-AP5 and NBQX either extended or not to the 30-to 60-min period after DOM exposure, respectively. Antagonists were ineffective if applied with a 2-h delay, indicating the presence of a critical time window for neuronal protection after DOM exposure. Early effects correlated with neuronal swelling was seen as early as 10 min post-DOM, which has been linked to non-NMDAR-mediated depolarization and release of endogenous glutamate. That DOM toxicity is dictated by iGluRs is supported by the finding that increased efficacy and potency of DOM with in vitro neuronal maturation are positively correlated with elevated protein levels of iGluR subunits, including NR1, GluR1, GluR2/3, GluR5, and GluR6/7. We determined the time course of DOM excitotoxicity. At >10 mM maximal neuronal death occurs within 2 h, while doses 10 mM continue to produce death during the subsequent 22-h washout period, indicating a quicker progression of the neuronal death cascade with high DOM concentrations. Accordingly, NBQX applied 30 min post-DOM afforded better protection against low dose/prolonged duration (3 mM/24 h) than against high dose/brief duration exposure (50 mM/10 min). Interestingly, prior exposure to subthreshold DOM dose-dependently aggravated toxicity produced by a subsequent exposure to DOM. These findings provide greater insight into the complex properties underlying DOM toxicity, including the sequential involvement of multiple GluRs, greater potency with increasing neuronal maturation and protein levels of iGluRs, varying efficacy depending on dose, duration, and prior history of DOM exposure.

Domoic acid (DOM) is known to cause hippocampal neuronal damage and produces amnesic effects. We examined synaptic plasticity changes induced by DOM exposure in rat hippocampal CA1 region. Brief bath application of DOM to hippocampal slices produces a chemical form of long-term potentiation (LTP) of CA1 field synaptic potentials. The potentiation cannot be blocked by NMDA receptor antagonist MK-801 but can be blocked by the calcium-calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-62 or cAMP-dependent protein kinase (PKA) inhibitor H-89. DOM-potentiated slices show decreased autophosphorylated CaMKII (p-Thr286), an effect that is also dependent on the activity of CaMKII and PKA. Increased phosphorylation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit GluR1 (p-Ser831) was seen in DOM-potentiated slices. Therefore, aberrant regulation of CaMKII and GluR1 phosphorylation occurs after DOM application. In addition, tetanus-induced LTP as w...

BACKGROUND Domoic acid (DA) is a naturally occurring neurotoxin harmful to marine animals and humans. California sea lions exposed to DA in prey during algal blooms along the Pacific coast exhibit significant neurological symptoms, including epilepsy with hippocampal atrophy. OBSERVATIONS Here the authors describe a xenotransplantation procedure to deliver interneuron progenitor cells into the damaged hippocampus of an epileptic sea lion with suspected DA toxicosis. The sea lion has had no evidence of seizures after the procedure, and clinical measures of well-being, including weight and feeding habits, have stabilized. LESSONS These preliminary results suggest xenotransplantation has improved the quality of life for this animal and holds tremendous therapeutic promise.

Domoic acid, a marine neurotoxin causative of Amnesic Shellfish Poisoning (ASP) was first detected in Chilean shellfish in January 1997. The presence of domoic acid (DA) in shellfish extracts was determined by reverse-phase HPLC-UV. Domoic acid concentrations exceeded in some instances the maximum permitted level (MPL) of 20 mg kg-1 of tissue. The highest levels were found in mussels (Mytilus chilensis) and its presence was associated with diatom blooms of the genus Pseudo-nitzschia. Since the diatoms P. cf. australis and P. cf. pseudodelicatissima are frequent phytoplankton components with a wide distribution in Chilean coastal waters, a permanent ASP monitoring program was implemented by the National Fisheries Service (Sernapesca) in 2000. Analyses of live shellfish samples collected from production areas from Los Lagos Region (41 o 30' to 42 o 30' S) are reported from January 1999 to May 2021. A total of 94 from 57,882 samples (0.16%) were found to contain DA above 20 mg kg-1. Another 1,360 samples (2.35%) contained DA below MPL (0.01 to < 20 mg kg-1). Diatom blooms and domoic acid were detected every year. However, toxicity levels above MPL were observed only in nine of the 22 years of continuous monitoring. Regular increases in toxicity were observed mainly during the transition from spring to summer (October to March) with peaks during December and January. High detoxification rates of DA from mussels (T 1/2 < 4 ± 1 days) allowed the development of contingency plans during the blooms that minimized harvest closures. Despite its recurrent nature, the risk observed to date has been low, with no reported cases of poisoning in humans, marine mammals, or birds.

20 Several species of the marine diatom Pseudo-nitzschia can produce the neurotoxin domoic 21 acid that is responsible for the seafood-borne illness amnesic shellfish poisoning in humans, 22 marine wildlife mortalities, and prolonged closures of fisheries resulting in economic losses 23 to coastal communities. Since the year 2000, Pseudo-nitzschia species have been monitored 24 in the Pacific Ocean with the Continuous Plankton Recorder (CPR). This study used a 25 combination of scanning electron microscopy with high-throughput and Sanger sequencing of 26 CPR survey samples to compare the diversity of phytoplankton, including Pseudo-nitzschia 27 species, from the north-eastern Pacific Ocean over three climatically different years: 2002, 28 2005, and 2008. Using a Pseudo-nitzschia- specific primer set targeting a 320bp region of the 29 large subunit ribosomal DNA (rDNA), revealed spatially-separated communities of Pseudo- 30 nitszschia . The coastal region was dominated by a diverse a...

Several species of the marine diatom Pseudo-nitzschia can produce the neurotoxin domoic acid that is responsible for the seafood-borne illness amnesic shellfish poisoning in humans, marine wildlife mortalities and prolonged closures of fisheries resulting in economic losses to coastal communities. Since the year 2000, Pseudo-nitzschia species have been monitored in the Pacific Ocean with the Continuous Plankton Recorder (CPR). We used a combination of scanning electron microscopy with high-throughput and Sanger sequencing of CPR survey samples to compare the diversity of phytoplankton, including Pseudo-nitzschia species, from the northeastern Pacific Ocean over 3 climatically different years: 2002, 2005 and 2008. A Pseudonitzschia-specific primer set targeting a partial region of the large subunit ribosomal DNA (rDNA) revealed spatially separated communities of Pseudo-nitzschia. The coastal region was dominated by a diverse array of P. fraudulenta unique sequences (operational taxonomic units), whereas the offshore region was rich in P. multiseries and contained a wide range of other Pseudo-nitzschia taxa, many not previously observed in this region. In 2008, exceptionally cold sea surface temperatures were recorded, influenced by a strong negative Pacific Decadal Oscillation signal. In that year, a more diverse assemblage of species was present in a spring open water sample, whereas P. fraudulenta was unusually rare from a coastal autumn sample. This is the first application of high-throughput genetic methods to uncover patterns of Pseudo-nitzschia genetic diversity from archival CPR samples, demonstrating the value of using CPR for plankton community analysis in rarely sampled regions of the oceans.

Some diatoms of the genera Pseudo-nitzschia and Nitzschia produce the neurotoxin domoic acid (DA), a compound that caused amnesic shellfish poisoning (ASP) in humans just over 30 years ago (December 1987) in eastern Canada. This review covers new information since two previous reviews in 2012. Nitzschia bizertensis was subsequently discovered to be toxigenic in Tunisian waters. The known distribution of N. navis-varingica has expanded from Vietnam to Malaysia, Indonesia, the Philippines and Australia. Furthermore, 15 new species (and one new variety) of Pseudo-nitzschia have been discovered, bringing the total to 52. Seven new species were found to produce DA, bringing the total of toxigenic species to 26. We list all Pseudo-nitzschia species, their ability to produce DA, and show their global distribution. A consequence of the extended distribution and increased number of toxigenic species worldwide is that DA is now found more pervasively in the food web, contaminating new marine organisms (especially marine mammals), affecting their physiology and disrupting ecosystems. Recent findings highlight how zooplankton grazers can induce DA production in Pseudo-nitzschia and how bacteria interact with Pseudo-nitzschia. Since 2012, new discoveries have been reported on physiological controls of Pseudo-nitzschia growth and DA production, its sexual reproduction, and infection by an oomycete parasitoid. Many advances are the result of applying molecular approaches to discovering new species, and to understanding the population genetic structure of Pseudo-nitzschia and mechanisms used to cope with iron limitation. The availability of genomes from three Pseudo-nitzschia species, coupled with a comparative transcriptomic approach, has allowed advances in our understanding of the sexual reproduction of Pseudo-nitzschia, its signaling pathways, its interactions with bacteria, and genes involved in iron and vitamin B 12 and B 7 metabolism. Although there have been no new confirmed cases of ASP since 1987 because of monitoring efforts, new blooms have occurred. A massive toxic Pseudo-nitzschia bloom affected the entire west coast of North America during 2015-2016, and was linked to a 'warm blob' of ocean water. Other smaller toxic blooms occurred in the Gulf of Mexico and east coast of North America. Knowledge gaps remain, including how and why DA and its isomers are produced, the world distribution of potentially toxigenic Nitzschia species, the prevalence of DA isomers, and molecular markers to discriminate between toxigenic and non-toxigenic species and to discover sexually reproducing populations in the field. 1989; Hanic, 2014). Since then, no additional deaths have been confirmed due to Amnesic Shellfish Poisoning (ASP), the syndrome caused by DA, although the prevalence of DA, its isomers, and toxic diatoms, has increased worldwide. This is because of increased monitoring, research and awareness, but is most certainly also due to limited medical awareness of ASP.

Diatom blooms generated by the alleviation of iron limitation in high nitrate-low chlorophyll (HNLC) regions of the oceans often are composed of pennate diatoms of the genus Pseudo-nitzschia, many of which periodically produce the potent neurotoxin domoic acid. We show that toxigenic diatoms have an inducible high-affinity iron uptake capability that enables them to grow efficiently on iron complexed by strong organic ligands in seawater. This low-iron adaptive strategy requires copper and domoic acid, a copper chelator whose production increases sharply when both iron and copper are limiting. Addition of either domoic acid or copper to seawater improves the growth of Pseudo-nitzschia spp. on strongly complexed iron during deck incubation experiments with natural phytoplankton. Our findings indicate that domoic acid is a functional component of the unusual high-affinity iron acquisition system of these organisms. This system may help explain why Pseudo-nitzschia spp. are persistent seed populations in oceanic HNLC regions, as well as in some neritic regions. Our findings also indicate that in the absence of an adequate copper supply, iron-limited natural populations of Pseudo-nitzschia will become increasingly toxic.

Spatial and temporal trends of marine harmful algal events in Canada over the last three decades were examined using data from the Harmful Algal Event Database (HAEDAT). This database contains the most complete record of algal blooms, phycotoxins and shellfish harvesting area closures in Canada since 1987. This 30-year review of 593 Canadian HAEDAT records from 1988 to 2017, together with other Canadian data and publications, shows that recurring harmful algal events have been widespread throughout both the Atlantic and Pacific coastal regions. The 367 paralytic shellfish toxin (PST) reports revealed annual and frequent recurrence throughout both the Atlantic and Pacific regions, including multi-year PST events in the Bay of Fundy, the Estuary and Gulf of St. Lawrence and the Strait of Georgia. The 70 amnesic shellfish toxin (AST) records revealed no recognizable trend, as these events were usually area specific and did not recur annually. The increasing frequency of diarrhetic shellfish toxin (DST) events over the period of this review, in total 59 records, can be at least partially explained by increased sampling effort. Marine species mortalities caused by harmful algae (including diatoms, dictyochophytes, dinoflagellates, and raphidophytes), were a common occurrence in the Pacific region (87 reports), but have been reported much less frequently in the Atlantic region (10 reports). Notable Canadian records contained in HAEDAT include the first detection worldwide of amnesic shellfish poisoning (ASP), attributed to the production of domoic acid (an AST) by a diatom (Pseudo-nitzschia multiseries) in Prince Edward Island in 1987. The first proven case of diarrhetic shellfish poisoning (DSP) in Canada and North America was recorded in 1990, and the first closures of shellfish harvesting due to DST (associated with the presence of Dinophysis norvegica) occurred in Nova Scotia in 1992, followed by closures in Newfoundland and Labrador in 1993. In 2008, mass mortalities of fishes, birds and mammals in the St. Lawrence Estuary were caused by Alexandrium catenella and high levels of PST. During 2015, the Pacific coast experienced a large algal bloom that extended from California to Alaska. It resulted in the closure of several shellfish harvesting areas in British Columbia due to AST, produced by Pseudo-nitzschia australis. Data from the Canadian Arctic coast is not included in HAEDAT. However, because of the emerging importance of climate change and increased vessel traffic in the Arctic, information on the occurrence of harmful algal species (pelagic and sympagic = sea ice-associated) in that region was compiled from relevant literature and data. The results suggest that these taxa may be more widespread than previously thought in the Canadian Arctic. Information in HAEDAT was not always robust or complete enough to provide conclusions about temporal trends. Compilation of spatial and temporal information from HAEDAT and other records is nevertheless important for evaluating the potential role of harmful algae as a

We report on the investigation of a mass stranding of 68 short-beaked common dolphins (Delphinus delphis) that occurred in Golfo Nuevo, Peninsula Valdes, Argentina in March 2018. Twenty-one of the stranded dolphins were returned alive to the sea, while 47 animals died. Dead dolphins included all ages, with more males than females (29 males and 18 females). The cause of death investigation reported here is restricted to 15 adult individuals and one fetus on which a full set of diagnostics was prioritized due to limited funding. Our results demonstrate that the death of 16 dolphins assessed in this study was not due to obvious human effects (e.g. bycatch) or underlying pathologies, as all animals were in good body condition and had no external evidence of injuries. Infections by Morbillivirus, Influenza A virus, Sarcocystis spp., Toxoplasma gondii, or Neospora caninum, as well domoic acid (DA) toxicity were ruled out as ethiologies in this event. Notably, results on exposure to paraly...

Peptaibols are small linear fungal peptides which are produced in the marine environment. They exhibit neurotoxicity by forming pores in neuronal membranes. This work describes their combine effect with domoic acid, a neurotoxic phycotoxin, on Diptera larvae. The Acute toxicity bioassay on this biological model was tested with a panel of different toxins (microbial, algal or fungal). It allowed the discrimination of neurotoxins and non-neurotoxic toxins, and an evaluation of the toxicity level (MED and ED 50) which were correlated with published LD 50 in mice for neurotoxins tested. The highest activities on this test were found for Na + channel blockers tetrodotoxin (ED 50 = 0.026 mg/kg) and saxitoxin (ED 50 = 0.18 mg/kg). Domoic acid was less active with an ED 50 = 7.6 mg/kg. For synergism study, longibrachin-A-I, a 20-mer peptaibol isolated from cultures of a marine-derived strain of Trichoderma longibrachiatum Rifai was chosen. Bioassay results confirmed its neuroactivity. Its level of toxicity (ED 50 = 270 mg/kg) was lower than those of phycotoxins tested but higher than mycotoxin ones. Injected together, longibrachin-A-I and domoic acid exhibited an increase of their activities. With doses of longibrachin-A-I below its Minimal Effective Dose (MED), the synergism factor which expresses the enhancement of domoic acid toxicity could reach 34.5. Both domoic acid and longibrachin-A-I are acting on ion channels and pores in neuronal membranes which contribute to the intake of Ca 2+ into cells.

A recent outbreak of marine food poisoning in humans was attributed to the consumption of blue mussels (Mytilus edulis L.) contaminated with domoic acid (DA) that was produced by the diatom Nitzschia pungens. The clinical and morphological effects of single oral doses of extracts of mussels contaminated with DA or of DA isolated from toxic mussels were investigated in small groups (one to six) ofcynomolgus monkeys (Macacafascicularis; 0.5-10 mg DA/kg body weight) and of Sprague Dawley rats (60 to 80 mg DA/kg body weight). Control animals were either given saline or were not treated. To test whether monosodium glutamate, present in the food consumed by some affected humans, and dimethylsulphoxide, suspected of being present in the plankton, enhanced the response, monosodium glutamate (at 0.25% of mussel extract bolus) or dimethylsulphoxide (at 1 g per bolus) were co-administered to two (one each) of the DA-treated monkeys. DA-treated monkeys developed transient excitation characterized by vomiting. DA-treated rats showed withdrawal followed by hyperexcitation and death (in one case). Mild to moderate central nervous system lesions consistent with neuroexcitation were present in both monkeys and rats. The addition of monosodium glutamate and dimethylsulphoxide had no significant effect on the appearance and severity of central nervous system clinical signs and lesions. The wide variations in the response of test animals to orally administered DA were attributed to the protective effect of vomiting, and to suspected incomplete or slow gastro-intestinal absorption of the toxic agent. The results reinforce the view that DA is an emetic and that under appropriate conditions may also inflict excitotoxic central nervous system damage.

The IOC-ICES-PICES Harmful Algal Event Database (HAEDAT) was used to describe the diversity and spatiotemporal distribution of harmful algal events along the Atlantic margin of Europe from 1987 -2018. The majority of events recorded are caused by Diarrhetic Shellfish Toxins (DSTs). These events are recorded annually over a wide geographic area from southern Spain to northern Scotland and Iceland, and are responsible for annual closures of many shellfish harvesting areas. The dominant causative dinoflagellates, members of the morphospecies 'Dinophysis acuminata complex' and D. acuta, are common in the waters of the majority of countries affected. There are regional differences in the causative species associated with PST events; the coasts of Spain and Portugal with the dinoflagellates Alexandrium minutum and Gymnodinium catenatum, north west France/south west England/south Ireland with A. minutum, and Scotland/Faroe Islands/Iceland with A. catenella. This can influence the duration and spatial scale of PST events as well as the toxicity of shellfish. The diatom Pseudo-nitzschia australis is the most widespread Domoic Acid (DA) producer, with records coming from Spain, Portugal, France, Ireland and the UK. Amnesic Shellfish Toxins (ASTs) have caused prolonged closures for the scallop fishing industry due to the slow depuration rate of DA. Amendments to EU shellfish hygiene regulations introduced between 2002 and 2005 facilitated end-product testing and sale of adductor muscle. This reduced the impact of ASTs on the scallop fishing industry and thus the number of recorded HAEDAT events. Azaspiracids

Some diatoms belonging to the genus Pseudo-nitzschia produce the neurotoxin domoic acid (DA), which causes amnesic shellfish poisoning (ASP). In Europe, accumulation of DA in shellfish has led to shellfish harvesting closures in western Scottish waters since 1999. However, little is yet known of the temporal appearance and succession of Pseudo-nitzschia species and how this may relate to environmental forcing. A phytoplankton monitoring programme was established for almost 3 yr at a coastal station in western Scottish waters to study the diversity and seasonal variation of Pseudo-nitzschia species in relation to physical and chemical parameters of the water column. Samples were collected with a high temporal resolution. Annually repeatable seasonal patterns of Pseudo-nitzschia abundance were evident. Pseudo-nitzschia cells were categorised by shape and size into 2 groups, the 'delicatissima-group' and the 'seriata-group'. Cluster analysis demonstrated the different dynamics of the 2 Pseudo-nitzschia groups. The delicatissima-group was dominated in spring by non-toxic P. delicatissima, while the seriata-group occurred mainly during the summer months. Summer to autumn blooms of both groups were composed of several species, including toxic P. australis and P. seriata and potentially toxic P. pseudo-delicatissima. Redundancy analysis indicated that 31% of the variance in Pseudo-nitzschia spp. abundance could be explained by the measured environmental variables. The repeatable annual nature of the blooms suggests that deterministic forecasting of the timing of future toxic Pseudo-nitzschia spp. events may be an achievable goal.

In 1999, a 49,000 km2 area in western Scottish waters was closed to shellfish harvesting due to the amnesic shellfish poisoning (ASP) toxin domoic acid (DA). The only previously confirmed DA producer identified had been Pseudo‐nitzschia australis Frenguelli. The toxin has appeared every year since and has led to more harvesting closures. We isolated and cultured two strains of Pseudo‐nitzschia seriata f. seriata (P. T. Cleve) H. Peragallo from western Scottish waters in 2001 and 2002. They were identified using TEM analysis of their morphological fine structure and sequencing of the internal transcribed spacer (ITS)1, 5.8S, ITS2, and partial large subunit (LSU) rDNA. The morphology of the Scottish P. seriata f. seriata strains differed slightly, for example, in the number of poroid rows, from descriptions in identification keys. Comparison of P. seriata sequences with those of two co‐occurring Pseudo‐nitzschia australis isolates showed an overall divergence of only 0.012. Sequence d...

Una inusual muerte masiva de peces sucedio durante un florecimiento de diatomeas ocurrido del 10 de junio al 3 de julio en la Bahia de La Paz, Golfo de California. Los organismos dominantes fueron Pseudo-nitzschia spp. (2.4 x 106 cels L-1), Thalassiosira eccentrica (2.3 x 106 cels L-1) y Chaetoceros spp. (9.65 x 105 cels L-1). Se identificaron tres especies toxicas: una pertenece al complejo P. pseudodelicatissima, P. fraudulenta y P. pungens. La fucoxantina, con un pico de 9.3 μg L-1, fue el pigmento dominante durante el florecimiento. La temperatura superficial del mar en el transcurso del evento drasticamente se incremento de 19.0 °C a 27.0 °C, con valores de nitrogeno inorganico de 1.0 ± 0.6 μM y Si(OH)4 de 15.5 ± 8.0 μM. El contenido de acido domoico determinado por HPLC-UV fue bajo tanto en muestras de red con un rango de 24.0 a 52.0 ng por filtro como en tejido de almeja chocolata Megapitaria squalida (0.55 μg g-1) y almeja blanca Dosinia ponderosa (0.06 μg g-1). El analisis ...

This investigation is aimed at providing a baseline survey of the current status of the occurrence and spatio-temporal distribution of amnesic shellfish poisoning (ASP) and paralytic shellfish poisoning (PSP) in the Nigerian coast, Gulf of Guinea. The study applied the Jellett Rapid Test technique to algal samples collected from 8 states of South-south (SS) and Southwest (SW) zones of coastal Nigeria, spanning the Bight of Bonny to the Bight of Benin, in the Gulf of Guinea, during the rainy and dry seasons, to screen for the presence of the human syndromes of ASP and PSP produced by domoic acid and saxitoxin, respectively. Classified as low, medium, high and highest, various levels of these syndromes were detected across the length of the Nigerian coast. Comparatively, the SW region had more syndromes (PSP and ASP) (64%) than the SS (36%) region of Nigerian coast. The prevalence of PSP (68%) was more than ASP (31%) in both zones with rainy season also recording higher (27%) ASP and PSP for SW than SS (12%) zone. Seasonal consideration revealed that more syndromes (ASP and PSP) were recorded in the rainy season compared to the dry season. With the confirmed presence, spatial and temporal distribution of ASP and PSP in the coastal waters of Nigeria, the need for regular monitoring of algal syndromes and toxins screening is advocated.

Algal toxins may accumulate in fish and shellfish and thus cause poisoning in consumers of seafood. Such toxins and the algae producing them are regularly surveyed in many countries, including Europe, North America, Japan and others. However, very little is known regards the occurrence of such algae and their toxins in most African countries. This paper reports on a survey of phytoplankton and algal toxins in Nigerian coastal waters. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. During this study, the occurrence of the marine dinoflagellate toxins OA and PTX2 has been demonstrated in coastal waters of Nigeria, despite unfavourable environmental conditions, with regards to the low salinities measured. Hence shellfish samples should be monitored in future to assess the risk for public health through accumulation of such toxins in seafood.

Nitzschia pungens f. multiseries (clone NPARL) was grown in nonaxenic batch culture under a range of growth conditions. Domoic acid (DA) was not detected during exponential growth, but production promptly started at a rate of approximately 1 pg DA∙cell−1∙d−1 at the onset of the stationary phase, in this case induced by silicate limitation. Cellular DA reached a maximum of 7 pg∙cell−1; thereafter, DA production continued at the same rate, with cellular levels remaining relatively constant due to concurrent release of DA into the culture medium. DA production ceased in the absence of nitrogen during the stationary phase, but resumed when nitrate was added back to the medium. Low irradiance slowed the division rate and consequently delayed the attainment of the stationary phase, but DA production rates were comparable with the control once stationary phase was reached. Cells during the dark period of a light–dark cycle, or placed into darkness, or in the presence of the photosynthetic ...