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Toxins Oct 2023Cyanobacteria harmful algal blooms (cyanoHABs) can have impacts on human health, aquatic ecosystems, and the economy. Nutrient management is an important mitigation and...
Cyanobacteria harmful algal blooms (cyanoHABs) can have impacts on human health, aquatic ecosystems, and the economy. Nutrient management is an important mitigation and even remediation strategy. In this work, the paralytic shellfish toxin (PST)-producing (.) (Linnaeus) Ralfs ex Bornet & Flahault (now identified as sp.) single filament isolate NH-5 was grown in P-depleted media, N-depleted media, and complete BG-11 media. Growth and heterocyst and vegetative cells were monitored using dry weight and cell counts. Ultrasonication was used to separate heterocysts from vegetative cells. HPLC-FLD with post-column derivatization was used to determine the saxitoxin (STX) and neosaxitoxin (NEOSTX) concentration per cell. sp. NH-5 biomass was lower in the P-depleted media than in the N-depleted media and the control, though higher heterocyst counts were detected in the N-depleted media. The heterocyst toxin concentration was significantly higher compared to the vegetative cells for the N-depleted media, control, and P-depleted media. However, no significant differences were found among all preparations with regard to the STX-to-NEOSTX ratio. We conclude that N limitation induced higher heterocyst numbers and that N fixation activity is a factor behind the increase in the STX and NEOSTX production of sp. NH-5.
Topics: Humans; Nitrogen; Ecosystem; Toxins, Biological; Cyanobacteria; Aphanizomenon
PubMed: 37888642
DOI: 10.3390/toxins15100611 -
Toxins Dec 2023Marine pufferfish, which naturally possess tetrodotoxins (TTXs), selectively take up and accumulate TTXs, whereas freshwater pufferfish, which naturally possess...
Marine pufferfish, which naturally possess tetrodotoxins (TTXs), selectively take up and accumulate TTXs, whereas freshwater pufferfish, which naturally possess saxitoxins (STXs), selectively take up and accumulate STXs. To further clarify the TTXs/STXs selectivity in pufferfish, we conducted a TTX/STX administration experiment using , a euryhaline marine pufferfish possessing both TTXs and STXs. Forty nontoxic cultured individuals of were divided into a seawater group (SW, acclimated/reared at 33‱ salinity; = 20) and a brackish water group (BW, acclimated/reared at 8‱ salinity; = 20). An aqueous TTX/STX mixture was intrarectally administered (both at 7.5 nmol/fish), and five individuals/group were analyzed after 1-48 h. Instrumental toxin analyses revealed that both TTX and STX were taken up, transferred, and retained, but more STX than TTX was retained in both groups. TTX gradually decreased and eventually became almost undetectable in the intestinal tissue, while STX was retained at ~5-10% of the dose level, and only STX showed transient transfer in the liver. The BW group showed a faster decrease/disappearance of TTX, greater STX retention in the intestine, and greater STX transient transfer to the liver. Thus, appears to more easily accumulate STXs than TTXs, especially under hypoosmotic conditions.
Topics: Animals; Saxitoxin; Tetrodotoxin; Takifugu; Fresh Water; Liver
PubMed: 38251235
DOI: 10.3390/toxins16010018 -
Toxics Aug 2023Changes in food quality can dramatically impair zooplankton fitness, especially in eutrophic water bodies where cyanobacteria are usually predominant. Cyanobacteria are...
Changes in food quality can dramatically impair zooplankton fitness, especially in eutrophic water bodies where cyanobacteria are usually predominant. Cyanobacteria are considered a food with low nutritional value, and some species can produce bioactive secondary metabolites reported as toxic to zooplankton. Considering that cyanobacteria can limit the survival, growth and reproduction of zooplankton, we hypothesized that the dietary exposure of neotropical ( and ) to saxitoxin-producing cyanobacteria impairs feeding rates and fitness regardless of a high availability of nutritious algae. Life table and grazing assays were conducted with different diets: (1) without nutritional restriction, where neonates were fed with diets at a constant green algae biomass (as a nutritious food source), and an increasing cyanobacterial concentration (toxic and poor food source), and (2) with diets consisting of different proportions of green algae (nutritious) and cyanobacteria (poor food) at a total biomass 1.0 mg C L. In general, the presence of high proportions of cyanobacteria promoted a decrease in somatic growth, reproduction and the intrinsic rate of population increase () in both diets with more pronounced effects in the nutritionally restricted diet (90% ). A two-way ANOVA revealed the significant effects of species/clone and treatments in both assays, with significant interaction between those factors only in the second assay. Regarding the grazing assay, only was negatively affected by increased cyanobacterial proportions in the diet. In the life table assay with constant nutritious food, a reduction in the reproduction and the intrinsic rate of the population increase () of all species were observed. In conclusion, we found adverse effects of the toxic cyanobacterial strain on fitness, regardless of the constant amount of nutritious food available, proving the toxic effect of and that the nutritional quality of the food has a greater influence on the fitness of these animals.
PubMed: 37624198
DOI: 10.3390/toxics11080693 -
Environmental Science & Technology Aug 2023Current climate trends are likely to expand the geographic distribution of the toxigenic microalgae and concomitant phycotoxins, making intoxications by such toxins a...
Current climate trends are likely to expand the geographic distribution of the toxigenic microalgae and concomitant phycotoxins, making intoxications by such toxins a global phenomenon. Among various phycotoxins, saxitoxin (STX) acts as a neurotoxin that might cause severe neurological symptoms in mammals following consumptions of contaminated seafood. To derive a point of departure (POD) for human health risk assessment upon acute neurotoxicity induced by oral STX exposure, a physiologically based kinetic (PBK) modeling-facilitated quantitative to extrapolation (QIVIVE) approach was employed. The PBK models for rats, mice, and humans were built using parameters from the literature, experiments, and predictions. Available toxicity data for STX were converted to dose-response curves via the PBK models established for these three species, and POD values were derived from the predicted curves and compared to reported toxicity data. Interspecies differences in acute STX toxicity between rodents and humans were found, and they appeared to be mainly due to differences in toxicokinetics. The described approach resulted in adequate predictions for acute oral STX exposure, indicating that new approach methodologies, when appropriately integrated, can be used in a 3R-based chemical risk assessment paradigm.
Topics: Rats; Mice; Humans; Animals; Saxitoxin; Models, Biological; Mammals
PubMed: 37478462
DOI: 10.1021/acs.est.3c01987 -
Harmful Algae Aug 2023This study presents the first evidence that a diverse suite of phycotoxins is not only being actively produced by the toxigenic algal communities in the Canadian Arctic...
This study presents the first evidence that a diverse suite of phycotoxins is not only being actively produced by the toxigenic algal communities in the Canadian Arctic waters, but is also entering the marine food web. We detected measurable amounts of Amnesic Shellfish Toxins (ASTs) and Paralytic Shellfish Toxins (PSTs), as well as trace amounts of other lipophilic toxin groups including pectenotoxins, yessotoxins, and cyclic imines, in bivalves collected from the Canadian Beaufort Sea in 2014 and 2018. There appear to be species-specific differences in accumulation and retention of AST by Arctic bivalves, with significantly higher concentrations recorded in Nuculanidae than Propeamussiidae, likely reflecting physiological and allometric differences. We further confirm the omnipresence of potentially toxic taxonomically-versatile phytoplankton communities in the western Canadian Arctic comprising Pseudo-nitzschia delicatissima group, P. obtusa, Dinophysis acuminata, Prorocentrum minimum, Alexandrium tamarense, and Gymnodinium spp. Although measurements of actual toxicity levels and profiles of these species at the time of sampling fall outside of the scope of this study, we show that high abundance and competitive success of known AST-producers, Pseudo-nitzschia spp., are possible in Canadian Arctic waters. In 2014, a strong dominance of Pseudo-nitzschia spp. was observed at a few shallow coastal stations, representing nearly 40% of the total phytoplankton cell abundances with > 10 cells/L at the depth of maximum chlorophyll a. We further describe oceanographic conditions conducive to high abundances of toxin-producing algae, indicating that temperature is likely a key factor. Even though measured AST and PST concentrations in bivalve tissue remained well below the Health Canada's levels at which monitored fisheries would close, i.e., 5% and 4%, respectively, their presence demonstrate that phycotoxin accumulation is occurring in food webs of the Canadian Beaufort Sea. Yet, the phycotoxin production controls and trophic transfer mechanisms remain unknown. Canadian Arctic marine ecosystems are rapidly changing and temperatures are expected to continue to increase. Given that these changes simultaneously affect multiple, and often co-occurring, species of primary producers, adaptive capacity is likely to play an important role in the structure of phytoplankton communities in the Canadian Arctic.
Topics: Animals; Marine Toxins; Ecosystem; Chlorophyll A; Canada; Phytoplankton; Bivalvia; Diatoms
PubMed: 37544674
DOI: 10.1016/j.hal.2023.102474 -
Water Research Apr 2024Freshwater benthic algae form complex mat matrices that can confer ecosystem benefits but also produce harmful cyanotoxins and nuisance taste-and-odor (T&O) compounds....
Freshwater benthic algae form complex mat matrices that can confer ecosystem benefits but also produce harmful cyanotoxins and nuisance taste-and-odor (T&O) compounds. Despite intensive study of the response of pelagic systems to anthropogenic change, the environmental factors controlling toxin presence in benthic mats remain uncertain. Here, we present a unique dataset from a rapidly urbanizing community (Kansas City, USA) that spans environmental, toxicological, taxonomic, and genomic indicators to identify the prevalence of three cyanotoxins (microcystin, anatoxin-a, and saxitoxin) and two T&O compounds (geosmin and 2-methylisoborneol). Thereafter, we construct a random forest model informed by game theory to assess underlying drivers. Microcystin (11.9 ± 11.6 µg/m), a liver toxin linked to animal fatalities, and geosmin (0.67 ± 0.67 µg/m), a costly-to-treat malodorous compound, were the most abundant compounds and were present in 100 % of samples, irrespective of land use or environmental conditions. Anatoxin-a (8.1 ± 11.6 µg/m) and saxitoxin (0.18 ± 0.39 µg/m), while not always detected, showed a systematic tradeoff in their relative importance with season, an observation not previously reported in the literature. Our model indicates that microcystin concentrations were greatest where microcystin-producing genes were present, whereas geosmin concentrations were high in the absence of geosmin-producing genes. Together, these results suggest that benthic mats produce microcystin in situ but that geosmin production may occur ex situ with its presence in mats attributable to adsorption by organic matter. Our study broadens the awareness of benthic cyanobacteria as a source of harmful and nuisance metabolites and highlights the importance of benthic monitoring for sustaining water quality standards in rivers.
Topics: Animals; Humans; Microcystins; Saxitoxin; Taste; Odorants; Ecosystem; Cyanobacteria Toxins; Rivers; Naphthols; Tropanes
PubMed: 38401471
DOI: 10.1016/j.watres.2024.121357 -
Environmental Microbiome Jan 2024Fecal bacterial densities are proxy indicators of beach water quality, and beach posting decisions are made based on Beach Action Value (BAV) exceedances for a beach....
BACKGROUND
Fecal bacterial densities are proxy indicators of beach water quality, and beach posting decisions are made based on Beach Action Value (BAV) exceedances for a beach. However, these traditional beach monitoring methods do not reflect the full extent of microbial water quality changes associated with BAV exceedances at recreational beaches (including harmful cyanobacteria). This proof of concept study evaluates the potential of metagenomics for comprehensively assessing bacterial community changes associated with BAV exceedances compared to non-exceedances for two urban beaches and their adjacent river water sources.
RESULTS
Compared to non-exceedance samples, BAV exceedance samples exhibited higher alpha diversity (diversity within the sample) that could be further differentiated into separate clusters (Beta-diversity). For Beach A, Cyanobacterial sequences (resolved as Microcystis and Pseudanabaena at genus level) were significantly more abundant in BAV non-exceedance samples. qPCR validation supported the Cyanobacterial abundance results from metagenomic analysis and also identified saxitoxin genes in 50% of the non-exceedance samples. Microcystis sp and saxitoxin gene sequences were more abundant on non-exceedance beach days (when fecal indicator data indicated the beach should be open for water recreational purposes). For BAV exceedance days, Fibrobacteres, Pseudomonas, Acinetobacter, and Clostridium sequences were significantly more abundant (and positively correlated with fecal indicator densities) for Beach A. For Beach B, Spirochaetes (resolved as Leptospira on genus level) Burkholderia and Vibrio sequences were significantly more abundant in BAV exceedance samples. Similar bacterial diversity and abundance trends were observed for river water sources compared to their associated beaches. Antibiotic Resistance Genes (ARGs) were also consistently detected at both beaches. However, we did not observe a significant difference or correlation in ARGs abundance between BAV exceedance and non-exceedance samples.
CONCLUSION
This study provides a more comprehensive analysis of bacterial community changes associated with BAV exceedances for recreational freshwater beaches. While there were increases in bacterial diversity and some taxa of potential human health concern associated with increased fecal indicator densities and BAV exceedances (e.g. Pseudomonas), metagenomics analyses also identified other taxa of potential human health concern (e.g. Microcystis) associated with lower fecal indicator densities and BAV non-exceedances days. This study can help develop more targeted beach monitoring strategies and beach-specific risk management approaches.
PubMed: 38225663
DOI: 10.1186/s40793-024-00547-8 -
Toxins Jul 2023Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for...
Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for these toxins in shellfish flesh has been adopted by many countries. In a recent study, mice were dosed with saxitoxin and tetrodotoxin mixtures daily for 28 days showing toxicity at low concentrations, which appeared to be at odds with other work. To further investigate this reported toxicity, we dosed groups of mice with saxitoxin and tetrodotoxin mixtures daily for 21 days. In contrast to the previous study, no effects on mouse bodyweight, food consumption, heart rate, blood pressure, grip strength, blood chemistry or hematology were observed. Furthermore, no histological findings were associated with dosing in this trial. The dose rates in this study were 2.6, 3.8 and 4.9 times greater, respectively, than the highest dose of the previous study. As rapid mortality in three out of five mice was observed in the previous study, the deaths are likely to be due to the methodology used rather than the shellfish toxins. To convert animal data to that used in a human risk assessment, a 100-fold safety factor is required. After applying this safety factor, the dose rates used in the current study were 3.5, 5.0 and 6.5 times greater, respectively, than the acute reference dose for each toxin type set by the European Union. Furthermore, it has previously been proposed that tetrodotoxin be included in the paralytic shellfish poisoning suite of toxins. If this were done, the highest dose rate used in this study would be 13 times the acute reference dose. This study suggests that the previous 28-day trial was flawed and that the current paralytic shellfish toxin regulatory limit is fit for purpose. An additional study, feeding mice a diet laced with the test compounds at higher concentrations than those of the current experiment, would be required to comment on whether the current paralytic shellfish toxin regulatory limit should be modified.
Topics: Humans; Animals; Mice; Saxitoxin; Tetrodotoxin; Shellfish Poisoning; Shellfish; Seafood
PubMed: 37505706
DOI: 10.3390/toxins15070437 -
Marine Drugs Apr 2024The Drinking Water Directive (EU) 2020/2184 includes the parameter microcystin LR, a cyanotoxin, which drinking water producers need to analyze if the water source has...
The Drinking Water Directive (EU) 2020/2184 includes the parameter microcystin LR, a cyanotoxin, which drinking water producers need to analyze if the water source has potential for cyanobacterial blooms. In light of the increasing occurrences of cyanobacterial blooms worldwide and given that more than 50 percent of the drinking water in Sweden is produced from surface water, both fresh and brackish, the need for improved knowledge about cyanotoxin occurrence and cyanobacterial diversity has increased. In this study, a total of 98 cyanobacterial blooms were sampled in 2016-2017 and identified based on their toxin production and taxonomical compositions. The surface water samples from freshwater lakes throughout Sweden including brackish water from eight east coast locations along the Baltic Sea were analyzed for their toxin content with LC-MS/MS and taxonomic composition with 16S rRNA amplicon sequencing. Both the extracellular and the total toxin content were analyzed. Microcystin's prevalence was highest with presence in 82% of blooms, of which as a free toxin in 39% of blooms. Saxitoxins were found in 36% of blooms in which the congener decarbamoylsaxitoxin (dcSTX) was detected for the first time in Swedish surface waters at four sampling sites. Anatoxins were most rarely detected, followed by cylindrospermopsin, which were found in 6% and 10% of samples, respectively. As expected, nodularin was detected in samples collected from the Baltic Sea only. The cyanobacterial operational taxonomic units (OTUs) with the highest abundance and prevalence could be annotated to NIES-81 and the second most profuse cyanobacterial taxon to PCC 7914. In addition, two correlations were found, one between NIES-81 and saxitoxins and another between PCC 7914 and microcystins. This study is of value to drinking water management and scientists involved in recognizing and controlling toxic cyanobacteria blooms.
Topics: Sweden; Cyanobacteria; Microcystins; Lakes; Marine Toxins; Saxitoxin; Environmental Monitoring; RNA, Ribosomal, 16S; Bacterial Toxins; Cyanobacteria Toxins; Tandem Mass Spectrometry
PubMed: 38786590
DOI: 10.3390/md22050199