查看更多>>摘要：The paralytic shellfish toxin-producing dinoflagellate Gymnodinium catenatum is distributed worldwide and often forms massive blooms in coastal waters, which pose a major threat to economic development and human safety. Temperature is among the factors influencing the growth and toxin production of HABs species. However, the physiological and molecular responses of G. catenatum to cold and heat stress need more investigations. Here, we compared the growth, toxin production, and transcriptomes of G. catenatum (Xiamen Bay, China) at different temperatures. Both cold (15 degrees C) and heat (30 degrees C) stress suppressed the growth and chlorophyll a content of G. catenatum. Transcriptomic analysis revealed that carbon from growth-related processes was redirected toward fatty acid synthesis to enhance energy storage under cold stress; up-regulated cold shock proteins and RNA-binding proteins maintained the stability of nucleic acids. Antioxidant activity was enhanced under heat stress with energy and carbon skeletons derived from the light reaction and starch and leucine degradation. The increase in toxin production probably stemmed from the enhanced transcription of core toxin synthesis genes and the inhibition of cell division under cold stress, whereas heat stress markedly enhanced the expression of genes involved in toxin synthesis. This enhanced the ability of G. catenatum to survive over a range of temperatures, and the increased frequency and toxicity of its blooms have significant ecological and economic implications under future global warming.
查看更多>>摘要：Comparatively little is known about paralytic shellfish toxin (PST) accumulation by marine grazers, yet recurrent blooms of Alexandrium catenella have caused repeated closures of wild fisheries and require ongoing monitoring. To determine if the commercially harvested periwinkle Lunella undulata is at risk of PST uptake, a laboratory experiment was conducted exposing the herbivorous/detritovorous marine snails to either live or senescent Alexandrium catenella microalgae. After 21 days of exposure, the highest PST concentrations were observed in the viscera of animals in the senescent and live algal treatments (0.55+0.08 and 0.82+0.12 mg STX.2HCl eq./kg, respectively). No quantifiable PST was observed in the foot of animals from either exposure treatment. The PST profile in the viscera closely matched that of the microalgal source, suggesting PST uptake through direct grazing of L. undulata on vegetative A. catenella cells. Grazing activity remained unchanged throughout the exposure period across all treatments. However, periwinkles exposed to A. catenella were significantly slower to retract their foot in response to touch than those animals in the control treatment (first observed on days 7 and 11 in the dead and live algae treatments, respectively). This effect became more pronounced over time and coincided with higher PST concentrations. While righting speed did not differ between animals exposed to live microalgae and the control, those exposed to senescent algae were generally slower to right (observed from day 4 onwards). The implications of these findings for biotoxin management in periwinkles and related marine grazers are discussed.
查看更多>>摘要：The marine dinoflagellate Gymnodinium catenatum is known to produce saxitoxins (STXs) that are responsible for paralytic shellfish poisoning (PSP); however, the genes involved in STX synthesis are insufficiently understood. In the present study, we determined transcriptome sequences of toxic G. catenatum isolated from Korea (Gc-KR) and compared them with G. catenatum strains reported in other regions such as Spain (Gc-SP) and the United States (Gc-US). Toxin analysis showed that the Korean strain produced the toxins at 6.0 +/- 1.9 STXs eq fmol/cell. Comparative transcriptomics of the three strains identified more than 1000 homologs of nearly all STXs biosynthesis genes in dinoflagellates, except sxtB, sxtN, and sxtY. Gene expression analysis revealed similar sxt expression patterns across all strains, with the highest expression levels observed for sxtA and sxtG. Phylogenetic analysis of sxtA, sxtG, sxtI, sxtU, and sxtS revealed distinct evolutionary patterns, with sxtA being more conserved across G. catenatum, Alexandrium spp., and toxic cyanobacteria, particularly at the sxtA4 domain, suggesting its significance in STXs synthesis. Other sxt genes in G. catenatum showed distinct patterns and significant divergence from Alexandrium spp., suggesting independent acquisition in G. catenatum. Moreover, the absence of core genes, such as sxtB, indicates it may not be essential for STXs production in G. catenatum. These findings provide insight into the sxt candidate genes in G. catenatum, enhancing our understanding of STXs biosynthesis in dinoflagellates.
查看更多>>摘要：Cyanobacterial blooms are common in the Baltic Sea during summer, and even though several cyanobacteria are toxin producers, many organisms still ingest them as feed. These and other phytoplankton toxins can be detected in blue mussels accumulating over the season, which represents a potential health hazard for shellfish consumers. On a global scale, biotoxins therefore need to be quantified in shellfish before human consumption. We monitored 11 different groups of biotoxins in three blue mussel farms and the composition of 23 potentially toxin producing phytoplankton taxa from March to November 2022. None of the biotoxins were above available health guideline values nor regulated levels. However, the well-known cyanobacterial toxin in the Baltic Sea, nodularin, produced by Nodularia spumigena, was detected in net- and rope-farmed mussels throughout the summer, with the highest concentration of 47 mu g kg-1. In contrast, the less studied toxin cylindrospermopsin was only present in mussels in early spring and late fall (surface water temperature approx. 2-10 degrees C), with the maximum concentration of 19.7 mu g kg-1 in April, where Aphanizomenon is a potential producer, but yet not confirmed. Further, Dinophysis acuminata, a potential producer of Diarrhetic Shellfish Toxins (DSTs), was observed above warning levels at two sites with up to 2 400 individuals L-1, although the found concentration of 73 mu g kg-1 is below the regulated level for DST group (160 mu g kg-1). Altogether emphasizing that high species abundance does not necessarily result in a high toxin accumulation. On the other hand, mussels can serve effectively as indicator species, detecting the presence of novel toxins when producer abundance is low. As no period of the year was completely toxin-free, quantitative analysis is recommended when mussels are to be harvested.
查看更多>>摘要：Freshwater is a declining natural resource sensitive to anthropogenic impacts on the environment, now exacerbated by climate change and elevated global temperatures. Among modern predicaments associated with the Anthropocene are nuisance and harmful algal blooms (HABs), which typically correlate with eutrophication resulting in the rapid growth and overabundance of planktonic microalgae, including cyanobacteria. Regions of hypoxia are common following bloom collapse, and some species of microalgae produce potent toxins, intensifying environmental impacts. While there has been some success implementing mitigation strategies against common bloom-forming microalgae, their responses to treatments are inconsistent. Routine mitigation can be incredibly costly while not being entirely effective, warranting innovation in mitigation strategies. Ultimately, a significant reduction in nutrient loading has the greatest potential for successful mitigation yet is not feasible due to societal requirements. At present, eutrophication and water pollution associated with bloom events are treated on a case-by-case basis, which can be unique depending on the microalgae present. This review provides a comprehensive summary of nuisance and harmful bloom-forming taxa, driving environmental factors, and existing mitigation strategies unique to freshwater microalgae. The major groups of bloom-forming microalgae are discussed, integrating factors responsible for increasing blooms in a rapidly changing climate, including potential treatment strategies.
查看更多>>摘要：Several methods to monitor cyanobacteria exist, based partly on characteristics that differentiate cyanobacteria from other phytoplankton, such as pigmentation and morphology. However, it is not certain whether all methods give similar insights into the development and properties of a cyanobacterial bloom. It is important to understand the level of consistency of measurements, especially in the case of novel methods. In situ imaging flow cytometry provides community composition information at high frequency but has been little used for filamentous bloomforming cyanobacteria. To understand if different methods agree, we compared multi-year biomass data collected with Imaging FlowCytobot (IFCB), CytoSense (CS), phycocyanin (PC) and chlorophyll (Chl) a fluorescence, and turbidity sensors, light microscopy, and satellite-based Frequency of Cyanobacteria Accumulations (FCA). Continuous high-throughput data was recorded at Uto<spacing diaeresis> Atmospheric and Marine Research Station in the Baltic Sea during summers 2018-2022, along with samples for light microscopy and adjacent satellite observations. The IFCB cyanobacteria biomass pattern most closely resembled those of CS and PC fluorescence. IFCB also described the blooms similarly to FCA, and to some extent to turbidity, but differed from Chl a fluorescence. IFCB and light microscopy agreed on the bloom development and species composition but differed concerning exact biomass. Our study demonstrates that both IFCB and CS are suitable for studying filamentous cyanobacteria and that in situ imaging flow cytometry provides valuable support for cyanobacteria monitoring by yielding detailed high-frequency taxon-specific information. Still, the best overall coverage of rapid biological processes such as bloom development is achieved with the parallel use of multiple observation techniques.
查看更多>>摘要：Several outbreaks of ciguatera poisoning have been recorded in La Re<acute accent>union (SW Indian Ocean) since 1986. Toxicities and toxin profiles of fish from the Indian Ocean are poorly documented. In this work, a multidisciplinary study on the toxicity of fish from the Indian Ocean by neuro-2a cell-based assay was assessed, and the CTX-like compounds were evaluated by a magnetic bead-based immunoassay. The toxin profile is described by liquid chromatography coupled to tandem mass spectrometry and high-resolution mass spectrometry. The liver, muscle, and viscera of four fish specimens of three different species (one Lutjanus bohar, two Variola louti and one Carcharinus leucas) caught in the waters of La Re<acute accent>union were analysed. One of the V. louti specimens was obtained after a CP incident. Their toxicity values ranged between 0.01 and 2.69 mu g CTX1B equiv.center dot kg-1 in flesh, 1.60 and 6.50 mu g CTX1B equiv.center dot kg-1 in liver and 0.07 and 4.77 mu g CTX1B equiv.center dot kg-1 in viscera. In general, liver and viscera showed higher concentrations of CTX-like compounds than flesh. Several potential CTX congeners were identified. LC-MS/MS confirmed the presence of CTX1B, 52-epi-54-deoxyCTX1B and 54-deoxyCTX1B in the flesh of the V. louti specimen involved in the CP incident. CTX1B was identified in the three tissues of the other V. louti individual and in the L. bohar. The C. leucas samples revealed the presence of a complex CTXs profile showing congeners of the CTX3C-group. The strategy used within this research work could be a valuable tool for future food safety monitoring in the Indian Ocean area.
NETL
NSTL
Elsevier