Articles de revues : « Toxic diatoms »

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Kumar, Rohit, Melania Paturzo, Angela Sardo, Ida Orefice, Qiucheng Yu, Andrea Rubano et Domenico Paparo. « Toxic Effect of Metal Doping on Diatoms as Probed by Broadband Terahertz Time-Domain Spectroscopy ». Molecules 27, n^o 18 (11 septembre 2022) : 5897. http://dx.doi.org/10.3390/molecules27185897.

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The global marine environment is increasingly affected by human activities causing climate change, eutrophication, and pollution. These factors influence the metabolic mechanisms of phytoplankton species, such as diatoms. Among other pollutant agents, heavy metals can have dramatic effects on diatom viability. Detailed knowledge of the interaction of diatoms with metals is essential from both a fundamental and applicative point of view. To this aim, we assess terahertz time-domain spectroscopy as a tool for sensing the diatoms in aqueous systems which mimic their natural environment. Despite the strong absorption of terahertz radiation in water, we show that diatoms can be sensed by probing the water absorption enhancement in the terahertz range caused by the water–diatom interaction. We reveal that the addition of metal dopants affects this absorption enhancement, thus enabling the monitoring of the toxic effects of metals on diatoms using terahertz spectroscopy. We demonstrate that this technique can detect the detrimental effects of heavy metals earlier than conventional methods such as microscopy, enzymatic assays, and molecular analyses aimed at assessing the overexpression of genes involved in the heavy metal-stress response.

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Chasapis, Christos T., Massimiliano Peana et Vlasoula Bekiari. « Structural Identification of Metalloproteomes in Marine Diatoms, an Efficient Algae Model in Toxic Metals Bioremediation ». Molecules 27, n^o 2 (7 janvier 2022) : 378. http://dx.doi.org/10.3390/molecules27020378.

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The biosorption of pollutants using microbial organisms has received growing interest in the last decades. Diatoms, the most dominant group of phytoplankton in oceans, are (i) pollution tolerant species, (ii) excellent biological indicators of water quality, and (iii) efficient models in assimilation and detoxification of toxic metal ions. Published research articles connecting proteomics with the capacity of diatoms for toxic metal removal are very limited. In this work, we employed a structural based systematic approach to predict and analyze the metalloproteome of six species of marine diatoms: Thalassiosira pseudonana, Phaeodactylum tricornutum, Fragilariopsis cylindrus, Thalassiosira oceanica, Fistulifera solaris, and Pseudo-nitzschia multistriata. The results indicate that the metalloproteome constitutes a significant proportion (~13%) of the total diatom proteome for all species investigated, and the proteins binding non-essential metals (Cd, Hg, Pb, Cr, As, and Ba) are significantly more than those identified for essential metals (Zn, Cu, Fe, Ca, Mg, Mn, Co, and Ni). These findings are most likely related to the well-known toxic metal tolerance of diatoms. In this study, metalloproteomes that may be involved in metabolic processes and in the mechanisms of bioaccumulation and detoxification of toxic metals of diatoms after exposure to toxic metals were identified and described.

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Hetko, Dominika, Małgorzata Witak et Magdalena Bełdowska. « The Relationship between Total Mercury, Its Fractions and Species Diversity of Diatom Taphocoenoses Deposited in Surface Sediments (Southern Baltic Sea) ». Water 15, n^o 22 (9 novembre 2023) : 3907. http://dx.doi.org/10.3390/w15223907.

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Mercury is a toxic metal that in excessive amounts negatively affects the human nervous system. It can biomagnify to enrich successive levels of the trophic web with higher and higher concentrations of Hg. Diatoms are cosmopolitan microalgae that represent the base of the trophic web. The objective of this study was to determine the importance of diatoms in the accumulation of Hg in surface sediments in the example of Puck Lagoon (southern Baltic Sea). The study verified the relationship of mercury forms with diatoms’ characteristic salinity groups and individual diatom species. The identified diatom flora permitted the distinguishment of three regions with different salinity preferences. The obtained results suggest that, together with organic matter and fine sediment fraction, diatoms are an important element of the marine environment in accumulating Hg. Area I, dominated by euhalobous and mesohalobous diatom species, was characterized by a high statistically significant correlation of mesohalobous with HgSO4, Hg in complexes with organic matter and HgS. In Area II, associated with the highest Hg concentrations (ca. 100 ng g−1), euhalobous showed a statistically significant linear correlation with HgSO4. In contrast, in Area III, the freshwater diatom community was associated with stable Hg forms. The identified species showed a connection with labile forms of Hg that can undergo biomagnification.

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Thessen, A. E., T. M. Soniat, Q. Dortch et G. J. Doucette. « Crassostrea virginica grazing on toxic and non-toxic diatoms ». Toxicon 55, n^o 2-3 (février 2010) : 570–79. http://dx.doi.org/10.1016/j.toxicon.2009.10.011.

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Giri, Tapas, Umesh Goutam, Aditi Arya et Shristy Gautam. « Effect of Nutrients on Diatom Growth : A Review ». Trends in Sciences 19, n^o 2 (3 janvier 2022) : 1752. http://dx.doi.org/10.48048/tis.2022.1752.

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Diatoms are one of the unicellular algae with a rare presence of unaltered, durable, transparent and species-specific silica frustules that persist even after cell death in the deposits of water bodies. Diatom has high capacity for absorption of metals for maintaining the water quality and high rate of multiplication. These characters promoted the use of this microbial biomass for effluent detoxification. These diatoms can also solve metal toxicity problems in aquatic ecosystems in the water polluted environment. In the present review, the focus is on several nutrients (nitrogen, phosphorus, iron and silica) that are essential for the growth of diatoms at very low concentrations, but most of them are toxic at high concentrations. It also shows the relationship between heavy metal stress and lipid body induction which may be a valuable indicator for the evaluation of heavy metal contamination of fluvial ecosystems. HIGHLIGHTS Diatoms are eukaryotic, unicellular, photosynthetic, silica-containing microscopic algae with distinct geometric forms Diatoms are used for biomonitoring purposes for taxonomic and morphological properties of ecosystems, community and human disturbances Diatoms are also the primary producer of oil in the world responsible for fixing 25 % of CO2 and 30 % of crude oil diatoms Many diatoms are appropriate for lipid development up to 70 % of their body volume and are investigated for biofuel as a hotspot GRAPHICAL ABSTRACT

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Tanković, Mirta Smodlaka, Ana Baričević, Victor Stinga Perusco, Roland R. Melzer, Alejandro Izquierdo Lopez, Jana Sophie Dömel, Martin Heß, Nataša Kužat, Daniela Marić Pfannkuchen et Martin Pfannkuchen. « Experimental evidence for shaping and bloom inducing effects of decapod larvae of Xantho poressa (Olivi, 1792) on marine phytoplankton ». Journal of the Marine Biological Association of the United Kingdom 98, n^o 8 (26 juillet 2018) : 1881–87. http://dx.doi.org/10.1017/s0025315418000449.

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To study zooplankton–phytoplankton relationships in the diatom-dominated plankton communities of the northern Adriatic we performed feeding experiments with diatoms and zoea I larvae of the brachyuran Xantho poressa. We found that zoea I of X. poressa feed on diatoms of different forms (centric, pennate, colony forming, single celled, with or without setae) and size classes. In a laboratory setup, we presented the zoeas with a mix of diatom species similar to communities observed during blooms regularly found in the northern Adriatic. We report that the grazing activity resulted in a decrease of the relative abundance of the toxic diatom Pseudo-nitzschia calliantha. For the colonial, bloom-forming diatom Skeletonema marinoi our results show a chain length reduction in the presence of zoea I. Of particular interest is the observation that the presence of larvae also resulted in an increased growth rate and abundance of S. marinoi, which resembles bloom induction by grazer presence.

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Khanaychenko, A. N. « How diatom Cylindrotheca closterium vanquish invasive copepod Oithona davisae ». Marine Biological Journal 3, n^o 3 (28 septembre 2018) : 77–85. http://dx.doi.org/10.21072/mbj.2018.03.3.08.

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Some diatoms are rich food for herbivorous copepods, while others are toxic for their recruitment. No negative effect of diatom Cylindrotheca closterium was ever observed for copepods, and some estuarine copepods preferred it as a food. Data on grazing diatoms by abundant now in the Black Sea coastal waters invasive copepod Oithona davisae are still contradictory. Interaction of O. davisae and C. closterium, both having high colonizing potential and both typical for coastal waters, was studied in experimental culture. Two weeks after inoculation of C. closterium the cultured O. davisae was drastically fouled by globulous conglomerates of diatom cells. Diatom cells in “colonies” on copepod exoskeleton were interconnected by means of adhesive substances at one of their flexible ends at the point-wise areas at various parts of copepods exoskeleton, and the opposite flexible ends performed various circular roll-over fan-shaped movements around the axis passing through the point of their attachment. “Colonies” behaved as integrated aggressive organisms against any approaching flagellate and prevented normal locomotion of copepods. Herein we present the first report on epizoic behavior of C. closterium: quick disastrous colonization of alive copepods O. davisae by diatom “colonies” led to total extinction of cyclopoid experimental population while alive diatoms formed dense network on copepods degenerative tissues.

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Perrin, C. J., et M. L. Bothwell. « Chlorate Discharges from Pulp Mills : An Examination of Effects on River Algal Communities ». Water Quality Research Journal 27, n^o 3 (1 août 1992) : 473–86. http://dx.doi.org/10.2166/wqrj.1992.032.

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Abstract To avoid the formation of organochlorine compounds in pulp products and effluents discharged into the environment, there is a trend in the North American pulping industry to change from molecular chlorine to chlorine dioxide bleaching. However, chlorate (ClO3−) formed during chlorine dioxide bleaching is known to have toxic effects in some marine algae and has been implicated in environmental problems in the Baltic Sea. This study examined the potential effects of chlorate on natural freshwater, riverine diatom communities characteristic of many rivers in western Canada. Under low ambient river nitrate concentrations (ca. 10 µg•L−1 NO3−N), chlorate additions of up to 500 µg•L1 ClO3 did not reduce the specific growth rates (µ) or change the taxonomic composition of the attached riverine diatom community. The lack of chlorate toxicity to freshwater diatoms suggests that the nitrate uptake and/or reduction mechanism(s) of freshwater diatoms have much higher affinities for NO3 than ClO3 compared to many marine macroalgae. These results indicate that chlorate discharged from new or upgraded pulpmills into freshwater river environments will not cause environmental changes to the dominant algal producers such as diatoms.

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Delasoie, Joachim, Natasa Radakovic, Aleksandar Pavic et Fabio Zobi. « Neovascularization Effects of Carbon Monoxide Releasing Drugs Chemisorbed on Coscinodiscus Diatoms Carriers Characterized by Spectromicroscopy Imaging ». Applied Sciences 10, n^o 20 (21 octobre 2020) : 7380. http://dx.doi.org/10.3390/app10207380.

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Silica microparticles made of diatomaceous earth have become particularly attractive materials for designing drug delivery systems. In order to investigate the use of natural diatoms as drug scaffolds for carbon monoxide releasing molecules (CORMs), we evaluated the chemisorption of the cis-[Re(CO)2Br4]2− complex (ReCORM-2) and its vitamin B12 derivative (B12-ReCORM-2) on Coscinodiscus frustules by 3D FT-IR spectroscopic imaging, and the drugs’ neovascularization effects in vivo in the zebrafish (Danio rerio) model. By mapping the symmetric Re-C≡O υ(CO) stretching vibration of the CORMs in the 2000 cm−1 region, we found that the drugs are mostly localized at the girdle band of the diatom frustule. Both ReCORM-2 and B12-ReCORM-2 retain their CO-releasing ability when chemisorbed on the diatoms. When applied in vivo at doses ≥25 µM, the molecules markedly reduced intersegmental and subintestinal vessels development in zebrafish, revealing high anti-angiogenic potential. In addition, diatom frustules did not provoke any toxic in vivo response in the zebrafish embryos, including inflammation. Overall, our results indicate that: (1) CORMs chemisorbed on diatom frustules retain their CO-releasing abilities; (2) both CO-releasing molecules show a concentration-dependent effect on the neovascularization in developing zebrafish; (3) silicate frustules are not toxic and could be used as CORMs drug carriers.

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Ianora A, , SA, A., A. Miralto et SA Poulet. « Are diatoms good or toxic for copepods ? » Marine Ecology Progress Series 177 (1999) : 305–8. http://dx.doi.org/10.3354/meps177305.

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Glaviano, Francesca, Nadia Ruocco, Emanuele Somma, Giuseppe De Rosa, Virginia Campani, Pasquale Ametrano, Davide Caramiello, Maria Costantini et Valerio Zupo. « Two Benthic Diatoms, Nanofrustulum shiloi and Striatella unipunctata, Encapsulated in Alginate Beads, Influence the Reproductive Efficiency of Paracentrotus lividus by Modulating the Gene Expression ». Marine Drugs 19, n^o 4 (17 avril 2021) : 230. http://dx.doi.org/10.3390/md19040230.

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Physiological effects of algal metabolites is a key step for the isolation of interesting bioactive compounds. Invertebrate grazers may be fed on live diatoms or dried, pelletized, and added to compound feeds. Any method may reveal some shortcomings, due to the leaking of wound-activated compounds in the water prior to ingestion. For this reason, encapsulation may represent an important step of bioassay-guided fractionation, because it may assure timely preservation of the active compounds. Here we test the effects of the inclusion in alginate (biocompatible and non-toxic delivery system) matrices to produce beads containing two benthic diatoms for sea urchin Paracentrotus lividus feeding. In particular, we compared the effects of a diatom whose influence on P. lividus was known (Nanofrustulum shiloi) and those of a diatom suspected to be harmful to marine invertebrates, because it is often present in blooms (Striatella unipunctata). Dried N. shiloi and S. unipunctata were offered for one month after encapsulation in alginate hydrogel beads and the larvae produced by sea urchins were checked for viability and malformations. The results indicated that N. shiloi, already known for its toxigenic effects on sea urchin larvae, fully conserved its activity after inclusion in alginate beads. On the whole, benthic diatoms affected the embryogenesis of P. lividus, altering the expression of several genes involved in stress response, development, skeletogenesis and detoxification processes. Interactomic analysis suggested that both diatoms activated a similar stress response pathway, through the up-regulation of hsp60, hsp70, NF-κB, 14-3-3 ε and MDR1 genes. This research also demonstrates that the inclusion in alginate beads may represent a feasible technique to isolate diatom-derived bioactive compounds.

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Zakharova, Yulia, Artem Marchenkov, Nadezhda Volokitina, Aleksey Morozov, Yelena Likhoshway et Mikhail Grachev. « Strategy for the Removal of Satellite Bacteria from the Cultivated Diatom ». Diversity 12, n^o 10 (3 octobre 2020) : 382. http://dx.doi.org/10.3390/d12100382.

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Multiple ecological and genetic studies of diatom algae require an axenic culture. However, algae-associated bacterial biofilms often form in diatom-produced mucus, both during creation of monoclonal cultures from single cells and during biomass growth, and they may be difficult to remove. In this work, we describe a protocol for removing associated bacteria from a monoclonal culture of Ulnaria danica isolated from Lake Baikal. The axenization strategy involves selecting the latent phase of diatom growth, multiple washes to remove extracellular polymeric substances and bacterial cells, filter deposition, and treatment with antibiotics that are not toxic for diatoms. The absence of bacteria during these stages was controlled by light microscopy with Alcian blue staining for mucus, epifluorescent microscopy with DAPI (4′,6-diamino-2-phenylindole) staining for bacterial DNA, and scanning electron microscopy of the diatom cell surface. High-throughput sequencing of a 16S rRNA fragment, amplified with universal bacterial primers, from total DNA of a final culture failed to detect any bacterial contamination, confirming successful axenization. A detailed comparative description of all stages of our protocol may prove useful in developing axenic cultures of other diatoms for various ecological and genetic studies.

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Delasoie, Joachim, et Fabio Zobi. « Natural Diatom Biosilica as Microshuttles in Drug Delivery Systems ». Pharmaceutics 11, n^o 10 (15 octobre 2019) : 537. http://dx.doi.org/10.3390/pharmaceutics11100537.

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Unicellular diatom microalgae are a promising natural resource of porous biosilica. These microorganisms produce around their membrane a highly porous and extremely structured silica shell called frustule. Once harvested from living algae or from fossil sediments of diatomaceous earth, this biocompatible and non-toxic material offers an exceptional potential in the field of micro/nano-devices, drug delivery, theranostics, and other medical applications. The present review focused on the use of diatoms in the field of drug delivery systems, with the aim of presenting the different strategies implemented to improve the biophysical properties of this biosilica in terms of drug loading and release efficiency, targeted delivery, or site-specific binding capacity by surface functionalization. The development of composite materials involving diatoms for drug delivery applications is also described.

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Ruocco, Nadia, Luisa Albarano, Roberta Esposito, Valerio Zupo, Maria Costantini et Adrianna Ianora. « Multiple Roles of Diatom-Derived Oxylipins within Marine Environments and Their Potential Biotechnological Applications ». Marine Drugs 18, n^o 7 (30 juin 2020) : 342. http://dx.doi.org/10.3390/md18070342.

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The chemical ecology of marine diatoms has been the subject of several studies in the last decades, due to the discovery of oxylipins with multiple simultaneous functions including roles in chemical defence (antipredator, allelopathic and antibacterial compounds) and/or cell-to-cell signalling. Diatoms represent a fundamental compartment of marine ecosystems because they contribute to about 45% of global primary production even if they represent only 1% of the Earth’s photosynthetic biomass. The discovery that they produce several toxic metabolites deriving from the oxidation of polyunsaturated fatty acids, known as oxylipins, has changed our perspectives about secondary metabolites shaping plant–plant and plant–animal interactions in the oceans. More recently, their possible biotechnological potential has been evaluated, with promising results on their potential as anticancer compounds. Here, we focus on some recent findings in this field obtained in the last decade, investigating the role of diatom oxylipins in cell-to-cell communication and their negative impact on marine biota. Moreover, we also explore and discuss the possible biotechnological applications of diatom oxylipins.

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COOKSEY, BARBARA, et KEITH E. COOKSEY. « Chemical signal-response in diatoms of the genus Amphora ». Journal of Cell Science 91, n^o 4 (1 décembre 1988) : 523–29. http://dx.doi.org/10.1242/jcs.91.4.523.

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The marine diatom Amphora coffeaeformis is positively chemotactic to glucose and sugars of similar structure. A free hydroxyl group is required at the 2-position of the ring; however, D-mannose (a toxic sugar) and L-glucose promote negative chemotaxis. Sugar metabolism is not necessary for a chemosensory response. When the direction of higher concentration in a D-glucose gradient is reversed, cells already orientated reverse their direction of movement. Pretreatment of diatoms with a uniform concentration of D-glucose before exposure to a concentration gradient eliminates the chemotactic response. When diatom cells attached to surfaces in the presence of 5mM-Ca2+ are exposed to 0.25-0.625 mM Ca2+, their motility drops rapidly. However, when this experiment is carried out in the presence of a uniform concentration of D-glucose or 3.O-methyl-D-glucose, motility is sustained for 25–30 min before falling. Speed of motility is also increased during this period. These results can be interpreted in terms of an agonist binding-secretion coupling model for diatom chemotaxis.

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Edwards, Bethanie R., Kimberlee Thamatrakoln, Helen F. Fredricks, Kay D. Bidle et Benjamin A. S. Van Mooy. « Viral Infection Leads to a Unique Suite of Allelopathic Chemical Signals in Three Diatom Host–Virus Pairs ». Marine Drugs 22, n^o 5 (17 mai 2024) : 228. http://dx.doi.org/10.3390/md22050228.

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Ecophysiological stress and the grazing of diatoms are known to elicit the production of chemical defense compounds called oxylipins, which are toxic to a wide range of marine organisms. Here we show that (1) the viral infection and lysis of diatoms resulted in oxylipin production; (2) the suite of compounds produced depended on the diatom host and the infecting virus; and (3) the virus-mediated oxylipidome was distinct, in both magnitude and diversity, from oxylipins produced due to stress associated with the growth phase. We used high-resolution accurate-mass mass spectrometry to observe changes in the dissolved lipidome of diatom cells infected with viruses over 3 to 4 days, compared to diatom cells in exponential, stationary, and decline phases of growth. Three host virus pairs were used as model systems: Chaetoceros tenuissimus infected with CtenDNAV; C. tenuissimus infected with CtenRNAV; and Chaetoceros socialis infected with CsfrRNAV. Several of the compounds that were significantly overproduced during viral infection are known to decrease the reproductive success of copepods and interfere with microzooplankton grazing. Specifically, oxylipins associated with allelopathy towards zooplankton from the 6-, 9-, 11-, and 15-lipogenase (LOX) pathways were significantly more abundant during viral lysis. 9-hydroperoxy hexadecatetraenoic acid was identified as the strongest biomarker for the infection of Chaetoceros diatoms. C. tenuissimus produced longer, more oxidized oxylipins when lysed by CtenRNAV compared to CtenDNAV. However, CtenDNAV caused a more statistically significant response in the lipidome, producing more oxylipins from known diatom LOX pathways than CtenRNAV. A smaller set of compounds was significantly more abundant in stationary and declining C. tenuissimus and C. socialis controls. Two allelopathic oxylipins in the 15-LOX pathway and essential fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were more abundant in the stationary phase than during the lysis of C. socialis. The host–virus pair comparisons underscore the species-level differences in oxylipin production and the value of screening more host–virus systems. We propose that the viral infection of diatoms elicits chemical defense via oxylipins which deters grazing with downstream trophic and biogeochemical effects.

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Merino-Virgilio, Fany Del Carmen, Yuri B. Okolodkov, Ana C. Aguilar-Trujillo et Jorge A. Herrera- Silveira. « Phytoplankton of the northern coastal and shelf waters of the Yucatan Peninsula, southeastern Gulf of Mexico, Mexico ». Check List 9, n^o 4 (1 août 2013) : 771. http://dx.doi.org/10.15560/9.4.771.

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Based on long-term monitoring (2001-2012) and four oceanographic cruises (2010-2012) in the coastal and shelf waters of the Yucatan Peninsula, SE Gulf of Mexico, a list of 306 strictly phytoplanktonic and tychoplanktonic species from 131 genera is presented: centric diatoms (83 species), raphid diatoms (47), araphid diatoms (22), Dinoflagellata (124), Cyanoprokaryota (18), Ebriacea (2), Chlorophyceae (3), Dictyochophyceae (2), Euglenophyceae (2), Cryptophyceae (1), Prymnesiophyceae (1), and Raphidophyceae (1). Diatoms also dominated the number of genera (80) followed by dinoflagellates (39) and cyanobacteria (11). The genera most abundant in species were Chaetoceros Ehrenb. (23 species), Protoperidinium Bergh (23) and Ceratium Schrank (17). The relative richness in species of the genus Oxytoxum (11 species) is related to the tropical affiliation of the phytoplankton community. Most of the tychoplanktonic diatoms (57 species out of a total of 152 diatoms, or 37.5%) were observed principally from coastal samplings. Eighteen potentially toxic species were found.

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Jónasdóttir, SH, T. Kiørboe, KW Tang, M. StJohn, AW Visser, E. Saiz et HG Dam. « Role of diatoms in copepod production:good, harmless or toxic ? » Marine Ecology Progress Series 172 (1998) : 305–8. http://dx.doi.org/10.3354/meps172305.

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Homer, Rita A., et James R. Postel. « Toxic diatoms in western Washington waters (U.S. west coast) ». Hydrobiologia 269-270, n^o 1 (octobre 1993) : 197–205. http://dx.doi.org/10.1007/bf00028018.

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Ruiz Gòmez, Anderson, et Jose Ernesto Mancera Pineda. « Potentially Toxic Dinoflagellates Associated to Seagrass on Isla de Barú, Colombian Caribbean, During El Niño ». Acta Biológica Colombiana 24, n^o 1 (1 janvier 2019) : 109–17. http://dx.doi.org/10.15446/abc.v24n1.61799.

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In the last decades, harmful algal blooms (HAB) and toxic events such as ciguatera seem to have increased in frequency and intensity, negatively impacting human health, economy, and marine ecosystems. In Colombia, these events have caused a series of consequences ranging from the death of fish and birds to toxic effects on humans. Although some toxin-producing dinoflagellate species are common in the Caribbean, their dynamics are poorly understood, making the adoption of any regulations difficult. To determine the composition and abundance of dinoflagellates associated with seagrasses we collected 18 samples on Isla de Barú, during 2015. We found ten diatom genera and three dinoflagellate genera, Prorocentrum, Ostreopsis, and Gambierdiscus, that include toxigenic species related to ciguatera and diarrheic shellfish poisoning. Prorocentrum lima was the most abundant dinoflagellate, with average cell densities of 52±48 cells/g substrate wet weight. The temperature hypothesis gains strength as one of the main modulators of dinoflagellate abundance observed in the Caribbean, especially regarding Prorocentrum species and some diatoms such as Mastogloia corsicana and Actinocyclus normanii. This assumption is supported by the Since high positive correlation between El Niño Southern Oscillation and the sea surface temperature in the Caribbean during 2015.

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MacPhee, Daniel J., Louis A. Hanic, Dianne L. Friesen et David E. Sims. « Morphology of the Toxin-Producing Diatom Nitzschia pungens Grunow forma multiseries Hasle ». Canadian Journal of Fisheries and Aquatic Sciences 49, n^o 2 (1 février 1992) : 303–11. http://dx.doi.org/10.1139/f92-034.

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The toxin-producing diatom Nitzschia pungens Grunow forma multiseries Hasle from three toxic blooms in two Prince Edward Island estuaries, spanning 1987–89, was studied using light and electron microscopy. Cell ultrastructure of N. pungens is, in general, similar to that of other species of Nitzschia and other diatoms. Important features include prominent peripheral, polarized nucleoli (numbering one or two) and imperforate poroids, present on inner valves and girdle bands. Cell division is usually synchronous for all cells in a filament with respect to polarity and time. Postdivisional elongation of the filament appears to involve a "slide-by" process whereby sibling cells slide by each other along their opposed valve faces and then stop, becoming fused by their overlapping tips. The raphe is probably involved in this, as well as in filament and cell motility. Observations of particle motion along the cell raphe suggest the existence of a motility apparatus such as microcilia which would facilitate locomotion, intercellular coordination, and the postdivisional slide-by process. No bacteria or other organisms were observed associated with field samples of toxic N. pungens f. multiseries. This supports a view that domoic acid production is autonomous.

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Azanza, Rhodora V., Nero M. Austero, Jenelle Clarisse R. Dungca, Frenchly Joyce O. Caspe et Lidita Khandeparker. « Phytoplankton and Bacterial Communities in South Harbour, Manila Bay, Philippines ». ASEAN Journal on Science and Technology for Development 35, n^o 1-2 (15 septembre 2018) : 107–13. http://dx.doi.org/10.29037/ajstd.480.

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In line with the ASEAN-India project “Extent of Transfer of Alien Invasive Organisms in South/Southeast Asia via Shipping”, phytoplankton and bacterial communities in the waters off South Harbour, Manila Bay were investigated. Sampling was done in July and August 2012 and in April and May 2013. A total of 67 phytoplankton species including 29 diatoms and 38 dinoflagellates were identified. Potentially toxic Pseudo-nitzschia spp. were among the diatoms found as well as dinoflagellates Alexandrium spp., and Gymnodinium spp. The diatom Skeletonema costatum appeared to be the dominant species in July and August 2012, whereas Chaetoceros spp. constituted over 85% of the total phytoplankton assemblage in April and May 2013. Mean bacterialabundance ranged from 9.53 x 102–3.18 x 105 cells/mL in July 2012. In addition, 93 bacterial isolates were identified using 16S rDNA, several of which belonged to the following phyla: Actinobacteria, Bacteriodetes, Firmicutes, and Proteobacteria; whereas, others were determined as uncultured bacterial clones. These results will serve as a valuable baseline for future studies on phytoplankton and bacterial community structure in Manila Bay.

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Sankaranarayanan, A., Muhammad Musthafa Poyil, Ponmurugan Karuppiah et Abubucker Peer Mohideen. « Effect of Physico-chemical Parameters on the Population Diversity of Potentially Harmful Micro-algae during Post-monsoon Season along the Malabar Coast ». Journal of Pure and Applied Microbiology 15, n^o 4 (22 novembre 2021) : 2382–93. http://dx.doi.org/10.22207/jpam.15.4.63.

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There are several toxic microalgae species known as Harmful algal bloom (HAB) causing serious effects to the environment and economy. Knowledge on these groups of marine micro-flora is scanty and several areas remain unexplored. The present study focuses on the analysis of microalgal diversity in the Malabar coastal areas at Southwest and Northeast monsoon. The diatoms, dinoflagellates and total microalgal population were analysed and quantified. Predominant species were identified. Physicochemical parameters of the seawater at different time intervals and Correlation between diatoms, dinoflagellates and total microalgae population with physicochemical parameters were identified. From the analysis, a total of 53 diatoms and 15 dinoflagellates were identified. The predominant species including toxic or harmful bloom-forming were found to be Dinophysis caudata, Noctiluca scintillans, Prorocentrum lima and Tripos furca. The total microalgae population varied from 18,592 cells/L to 7,832 cells/L in the months of April and December. Dinoflagellates were positively correlated with salinity (r = 0.848; p = 0.008), nitrite (r = 0.752; p = 0.032) and total phosphorous (r = 0.734, p = 0.038). Diatoms were positively correlated with temperature (r = 0.804; p = 0.016) and nitrate (r = 0.774, p = 0.024). Total microalgal density was positively correlated with temperature (r = 0.825; p = 0.012) and nitrate content (r = 0.811, p = 0.15).

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Li, S. X., F. J. Liu, F. Y. Zheng, Y. G. Zuo et X. G. Huang. « The role of iron species on the competition of two coastal diatoms, <i>Skeletonema costatum</i> ; and <i>Thalassosira weissflogii</i> ; ». Biogeosciences Discussions 10, n^o 12 (13 décembre 2013) : 19603–31. http://dx.doi.org/10.5194/bgd-10-19603-2013.

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Abstract. Coastal diatoms are often exposed to macronutrient (N and P) and Fe enrichment. However, how these exposures influence on Fe biogeochemical cycle and then on diatom interspecific competition is unknown. In this study, two non-toxic coastal diatoms, Skeletonema costatum and Thalassosira weissflogii were exposed to N, P, and Fe enrichment for four-day. The growth of algae was co-controlled by macronutrient and Fe species (Fe (III)-EDTA, Fe(OH)3, dissolved, colloidal, and particulate Fe from culture medium). The influence of Fe species on algal cell density was more significant than macronutrient. When S. costatum coexisted with T. weissflogii, their cell density ratios were ranged between 5.57–7.03 times, indicating that S. costatum was more competitive than T. weissflogii. There were not significant correlation between cell density ratio and iron requirement, including iron adsorption and absorption per cell, iron adsorption and absorption by all algal cells. As Fe complexing ligands, algal exudates can promote diatom growth itself and such promotion on S. costatum was more obvious than that on T. weissflogii. Iron species was a key determinant on interspecific competition of coastal diatom, and the degree of bioavailability was described as follows: dissolved iron from own exudates > colloidal iron from own exudates > particulate iron from own exudates > particulate iron from another algal exudates > colloidal iron from another algal exudates > dissolved iron from another algal exudates > Fe (III)-EDTA> Fe (OH)3.

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Motylkova, I. V., et N. V. Konovalova. « Structure of phytoplankton for the coastal waters in the eastern Aniva Bay of the Okhotsk Sea in 2018 ». Izvestiya TINRO 204, n^o 2 (2 juillet 2024) : 433–43. http://dx.doi.org/10.26428/1606-9919-2024-204-433-443.

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Species composition, distribution density and biomass of phytoplankton were surveyed in the coastal area of eastern Aniva Bay in May-October 2018. In total, 297 species and intraspecific taxa of microalgae belonged to Bacillariophyta, Chlorophyta, Cryptophyta, Dinophyta, Euglenophyta, Crysophyta were found. Their total abundance ranged from 14.8 . 103 to 1024.7 . 103 cells/L, biomass was 19.4–324.6 mg/m3. Two peaks in the abundance (in June and October) and five peaks in the biomass (in May, June, September and October) were noted. The bulk of population was formed by diatoms in spring and autumn, and flagellates in summer. A bloom of potentially toxic diatoms of genus Pseudo-nitzschia was registered. In this connection, monitoring of toxic species is necessary for planning and development of aquaculture farms.

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Kang, Sunggu, Yeeun Woo, Yoseph Seo, Daehyeon Yoo, Daeryul Kwon, Hyunjun Park, Sang Deuk Lee, Hah Young Yoo et Taek Lee. « A Descriptive Review on the Potential Use of Diatom Biosilica as a Powerful Functional Biomaterial : A Natural Drug Delivery System ». Pharmaceutics 16, n^o 9 (5 septembre 2024) : 1171. http://dx.doi.org/10.3390/pharmaceutics16091171.

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Although various chemically synthesized materials are essential in medicine, food, and agriculture, they can exert unexpected side effects on the environment and human health by releasing certain toxic chemicals. Therefore, eco-friendly and biocompatible biomaterials based on natural resources are being actively explored. Recently, biosilica derived from diatoms has attracted attention in various biomedical fields, including drug delivery systems (DDS), due to its uniform porous nano-pattern, hierarchical structure, and abundant silanol functional groups. Importantly, the structural characteristics of diatom biosilica improve the solubility of poorly soluble substances and enable sustained release of loaded drugs. Additionally, diatom biosilica predominantly comprises SiO2, has high biocompatibility, and can easily hybridize with other DDS platforms, including hydrogels and cationic DDS, owing to its strong negative charge and abundant silanol groups. This review explores the potential applications of various diatom biosilica-based DDS in various biomedical fields, with a particular focus on hybrid DDS utilizing them.

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Riouchi, Ouassila, Faid El Madani, Eric Abadie, Ali Skalli, Mustapha Akodad, Abdelmajid Moumen, Hanane Ait Hmeid, Ghizlane Azizi et Mourad Baghour. « Pseudo-Nitzschia sp (Bacillariophyceae), seasonal distribution in the lagoon of Nador (Morroco) ». E3S Web of Conferences 314 (2021) : 01003. http://dx.doi.org/10.1051/e3sconf/202131401003.

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The goal of this study is to look into the dominance of diatoms, specifically the genus “Pseudo-Nitzschia Sp” at the Nador lagoon level and how it relates to the physicochemical parameters of the environment. From the four sampling stations and for two seasons (spring and summer 2018). This diatom of the genus “Pseudo-Nitzschia Sp” includes toxic species capable of producing domoic acid (DA), a neurotoxin responsible for amnesic intoxication syndrome in humans. During sampling, the species “PseudoNitzschia Sp” showed variable cell densities between stations and seasons. The dominate microalgae were observed during the spring period with a maximum concentration of (4000 Cells / l). And a low viscosity during the summer seasons (140 Cells / l).

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Timmerman, Amanda H. V., Margaret A. McManus, O. M. Cheriton, Robert K. Cowen, Adam T. Greer, Raphael M. Kudela, Kathleen Ruttenberg et Jeff Sevadjian. « Hidden thin layers of toxic diatoms in a coastal bay ». Deep Sea Research Part II : Topical Studies in Oceanography 101 (mars 2014) : 129–40. http://dx.doi.org/10.1016/j.dsr2.2013.05.030.

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Díaz, Patricio A., Iván Pérez-Santos, Ángela M. Baldrich, Gonzalo Álvarez, Camila Schwerter, Michael Araya, Álvaro Aravena et al. « Small-Scale Biophysical Interactions and Dinophysis Blooms : Case Study in a Strongly Stratified Chilean Fjord ». Journal of Marine Science and Engineering 12, n^o 10 (29 septembre 2024) : 1716. http://dx.doi.org/10.3390/jmse12101716.

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Diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTXs) produced by endemic species of Dinophysis, mainly D. acuta and D. acuminata, threaten public health and negatively impact the shellfish industry worldwide. Despite their socioeconomic impact, research on the environmental drivers of DSP outbreaks in the Chilean fjords is scanty. From 22 to 24 March 2017, high spatial–temporal resolution measurements taken in Puyuhuapi Fjord (Northern Patagonia) illustrated the short-term (hours, days) response of the main phytoplankton functional groups (diatoms and dinoflagellates including toxic Dinophysis species) to changes in water column structure. Results presented here highlight the almost instantaneous coupling between time–depth variation in density gradients, vertical shifts of the subsurface chlorophyll maximum, and its evolution to a buoyancy-driven thin layer (TL) of diatoms just below the pycnocline the first day. A second shallower TL of dinoflagellates, including Dinophysis acuta, was formed on the second day in a low-turbulence lens in the upper part of the pycnocline, co-occurring with the TL of diatoms. Estimates of in situ division rates of Dinophysis showed a moderate growth maximum, which did not coincide with the cell density max. This suggests that increased cell numbers resulted from cell entrainment of off-fjord populations combined with in situ growth. Toxin profiles of the net tow analyses mirrored the dominance of D. acuminata/D. acuta at the beginning/end of the sampling period. This paper provides information about biophysical interactions of phytoplankton, with a focus on Dinophysis species in a strongly stratified Patagonian fjord. Understanding these interactions is crucial to improv predictive models and early warning systems for toxic HABs in stratified systems.

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Joseph, Mwangi. « Usage of human diatomaceous earth ». Annals of Limnology and Oceanography 8, n^o 1 (28 décembre 2023) : 009–12. http://dx.doi.org/10.17352/alo.000014.

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Diatomaceous earth is naturally formed sedimentary mineral rock resulting from the remains of diatoms, or oceanic unicellular algae. It is extracted from diatoms mined from deposits of diatomite and manufactured into a powder that is diatomaceous earth for human use, as a natural compound. It is gaining popularity as having an outstanding list of health benefits and non-toxic, no-known side effect origins. In this paper, a comprehensive review is presented to highlight the availability, benefits, mechanism of operation, and effects on the use of Human Diatomaceous Earth. The review revealed that diatomaceous earth has an outstanding list of health benefits and non-toxic, no-known side effects. It has the ability to lower the concentration of cholesterol in the blood. It is a very essential mineral for tendons, cartilage, blood vessels, and bones. Diatomaceous Earth is also considered to greatly help the body in getting rid of toxic substances such as heavy metals. It improves body joints bones, and ligaments through silica, which is the highest-occurring compound in diatomaceous earth that aids in the metabolism and formation of the joints.

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Mamanazarova, Karomat, Kholiskhon Alimjanova et Sophia Barinova. « Biodiversity of Diatoms as Indicators of Water Quality and Landscape Sustainable Dynamics in the Zarafshan River, Uzbekistan ». Land 13, n^o 11 (1 novembre 2024) : 1809. http://dx.doi.org/10.3390/land13111809.

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For the first time, we have compiled a general list of diatoms for the Zarafshan River consisting of 428 species based on our own research and the literature data. Indicator species for nine water parameters were identified, making up more than 90% of the list. Bioindicators and statistical methods revealed that sections of the river around the city of Samarkand and further in the middle reaches reflect the complexity of the impact of the environment on diatom communities. The surveyed sections of the middle reaches of the river are divided into branches and the dynamics of water parameters and diatom communities are shown from the border with Tajikistan to the confluence of the Zarafshan with the Amu Darya. The indices of organic pollution, S, and toxic impact, WESI, were calculated. They show that there is an increase in salinity and turbidity and a decrease in organic pollution downriver. At the same time, the Navoi section is a source of water acidification. Nutrients and heavy metals, as well as phenol pollution, enter the river from various sources, mainly in the middle reaches of the river. The Zarafshan Nature Reserve in the catchment area of the upper section of the river within Uzbekistan is important for maintaining water quality. Bioindicators show an increase in self-purification, with an increase in the species richness and abundance of diatoms in the middle section of the Zarafshan River. The integrated index of river pollution, RPI, shows that most pollution comes from the northern canal of the river in the middle reaches. A general look at the Zarafshan River catchment basin and the dynamics of the identified water parameters and bioindicator species of diatoms shows that the river ecosystem successfully copes with incoming pollution, including transboundary impacts from Tajikistan. Such a conclusion could not be made based on chemical analysis of the water alone. This allowed us to recommend expanding state monitoring points to the lower section of Karakul while including biological indicators in the observations.

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Rico-Virgen, Erika Guadalupe, Ismael Ortiz-Aguirre, Claire Hellio, Carlos Rangel-Dávalos, Anahí Escobedo-Fregoso, Francisco Omar López-Fuerte, María Concepción Lora-Vilchis et Ruth Noemí Aguila-Ramírez. « Antifouling activity of marine bacterial extracts : A non-toxic alternative as biocide ». Revista de Biología Marina y Oceanografía 59, n^o 1 (1 juin 2024) : 39–50. http://dx.doi.org/10.22370/rbmo.2024.59.1.4456.

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Biofouling is generated by the biochemical condition of the substrate to form complex communities; this could be negative at an ecological and industrial level. To inhibit this process, coatings based on heavy metals are used. Microorganisms are promising sources of antifouling compounds that are non-toxic or less toxic than the commercial chemicals in use today. In order to evaluate the antifouling effectiveness of bacterial extracts, seven crude extracts from cultures of bacteria isolated from marine organisms were obtained. They were subjected to a toxicity test with Artemia nauplii, at different concentrations. Non-toxic extracts were incorporated into a gelling agent (Phytagel™) and exposed to the sea for 30 days to evaluate the inhibition of diatoms and macroorganisms adhesion. Sixty-seven diatoms’ taxa were identified, belonging to 45 genera, besides four groups of non-photosynthetic macroorganisms were identified; these are sea squirts, barnacles, bryozoans, and polychaetes. Toxicity test showed that only Bacillus safensis (C2) extract was toxic, and it was excluded from subsequent tests. There are significant differences between treatments, the extracts with the best activity are Shewanella algae (18) and Staphylococcus aureus (28). These extracts contain different organic compounds such as saponins, terpenes, sterols, and proteins, which could be responsible for their activity. These results suggest that microorganisms are an effective alternative to replace harmful chemical substances currently used in antifouling coatings. The extracts, being less toxic, are potential inhibitors or retardants of the epibiotic colonization process.

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Hale, E. A., J. M. Krupp et D. L. Garrison. « SEM observations of bloom-forming toxic diatoms from Monterey Bay, California ». Proceedings, annual meeting, Electron Microscopy Society of America 50, n^o 1 (août 1992) : 832–33. http://dx.doi.org/10.1017/s0424820100124562.

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In the late summer of 1991, large numbers of seabirds in northern Monterey Bay, California died after showing unusual neurological symptoms. The first suspects were dinoflagellates, planktonic algae known to produce the toxins responsible for paralytic shellfish poisoning (PSP). Although toxic dinoflagellates were found, no evidence for PSP was present. Subsequent chemical analysis of tissue and stomach contents from affected birds and from locally collected northern anchovy showed high concentrations of domoic acid. During the seabird kill in Monterey Bay, the plankton was dominated by Pseudonitzschia australis (=Nitzschia pseudoseriata) a diatom not previously known to produce domoic acid.

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Minutoli, R., C. Brugnano, S. Casini, G. Mori et G. Zagami. « Biomarkers employment to show no effects of toxic diatoms on copepods ? » Comparative Biochemistry and Physiology Part A : Molecular & ; Integrative Physiology 157 (septembre 2010) : S27. http://dx.doi.org/10.1016/j.cbpa.2010.06.078.

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Khosrovyan, Alla, Rima Avalyan, Anahit Atoyants, Evelina Aghajanyan, Lusine Hambaryan, Rouben Aroutiounian et Bardukh Gabrielyan. « Tradescantia-Based Test Systems Can Be Used for the Evaluation of the Toxic Potential of Harmful Algal Blooms ». Water 15, n^o 13 (7 juillet 2023) : 2500. http://dx.doi.org/10.3390/w15132500.

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Harmful algal blooms (HABs) are overgrowths of toxic strains of algae (diatoms, green) and cyanobacteria (blue-green algae). While occurring naturally, human-induced environmental changes have resulted in more frequent occurrences of such blooms worldwide. Meantime, the ecotoxicological risk of HABs is rarely evaluated by means of standard test methods. For the first time, the genotoxic potential of the HAB event 2020 was assessed using two different Tradescantia-based test systems (Trad-SHM and Trad-MN, 24-h exposure). An integrated analysis of biological (algal abundance) and ecotoxicological (testing) data revealed linkages among algal proliferation, changes in Tradescantia stamen hairs (mutations and suppressed growth) and chromosomal aberrations during microsporogenesis (appearance of micronuclei) that were likely to be caused by toxic algal groups. Green alga Botryococcus braunii and the cyanobacterial species Anabaena and Oscillatoria could suppress stamen hair growth; Cyanobacteria Phormidium and Aphanothece sp. could trigger mutations in stamen hairs (appearance of pink and colorless cells); and Oscillatoria sp. could be responsible for the occurrence of chromosomal damage. Diatom proliferation in the spring was not related to the genotoxic response in Tradescantia. Both tests, the Trad-SHM and Trad-MN, are suitable for the evaluation of the toxic potential of HABs.

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Ruocco, Nadia, Genoveffa Nuzzo, Giuliana d’Ippolito, Emiliano Manzo, Angela Sardo, Adrianna Ianora, Giovanna Romano et al. « Lipoxygenase Pathways in Diatoms : Occurrence and Correlation with Grazer Toxicity in Four Benthic Species ». Marine Drugs 18, n^o 1 (19 janvier 2020) : 66. http://dx.doi.org/10.3390/md18010066.

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Oxygenated derivatives of fatty acids, collectively called oxylipins, are a highly diverse family of lipoxygenase (LOX) products well described in planktonic diatoms. Here we report the first investigation of these molecules in four benthic diatoms, Cylindrotheca closterium, Nanofrustulum shiloi, Cocconeis scutellum, and Diploneis sp. isolated from the leaves of the seagrass Posidonia oceanica from the Gulf of Naples. Analysis by hyphenated MS techniques revealed that C. closterium, N. shiloi, and C. scutellum produce several polyunsaturated aldehydes (PUAs) and linear oxygenated fatty acids (LOFAs) related to the products of LOX pathways in planktonic species. Diploneis sp. also produced other unidentified fatty acid derivatives that are not related to LOX metabolism. The levels and composition of oxylipins in the benthic species match their negative effects on the reproductive success in the sea urchin Paracentrotus lividus. In agreement with this correlation, the most toxic species N. shiloi revealed the same LOX pathways of Skeletonema marinoi and Thalassiosira rotula, two bloom-forming planktonic diatoms that affect copepod reproduction. Overall, our data highlight for the first time a major role of oxylipins, namely LOFAs, as info-chemicals for benthic diatoms, and open new perspectives in the study of the structuring of benthic communities.

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Paniagua-Michel, J., et Ibrahim M. Banat. « Unravelling Diatoms’ Potential for the Bioremediation of Oil Hydrocarbons in Marine Environments ». Clean Technologies 6, n^o 1 (17 janvier 2024) : 93–115. http://dx.doi.org/10.3390/cleantechnol6010007.

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The search for practical solutions to alleviate the destructive impact of petroleum hydrocarbons in marine environments is contributing to the implementation of prospecting strategies for indigenous microorganisms with biodegradative and bioremediation potential. The levels of petroleum contamination entering the marine environment each year have been estimated at around 1.3 million tonnes, a figure that is expected to increase by 1.9% annually over the next decade. The recent interest in decarbonizing our energy system and accelerating the clean energy transition has created a demand for greener technologies and strategies to find innovative, sustainable, and cost-effective treatments for the marine environment. Diatoms (Bacillariophyta) are one of the most diverse and successful taxa in coastal–marine environments and are a relatively untapped pool of biodiversity for biotechnological applications. Recent reports have revealed the significant presence of diatoms associated with oil spills and petroleum hydrocarbon degradation. Most diatoms can secrete substantial amounts of exopolysaccharides (EPSs) into their environment, which can act as biosurfactants that, in addition to oxygen and other enzymes produced by diatoms, create suitable conditions to enhance hydrocarbon solubility and degradation into less toxic compounds in seawater. Recent reports on the biodegradation of aliphatic and aromatic hydrocarbons by diatoms are indicative of the potential of these taxa to achieve success in the bioremediation of hydrocarbons in marine environments. This review highlights the main attributes and roles that diatoms could play in integrated strategies for biodegradation and bioremediation of petroleum hydrocarbon pollutants and as such represent a green, eco-friendly, and sustainable contribution to mitigate damage to biodiversity and value chains of marine ecosystems.

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Petrova, Darya P., Yekaterina D. Bedoshvili, Yulia R. Zakharova, Nadejda A. Volokitina, Yelena V. Likhoshway et Michael A. Grachev. « Changes in valve morphology of two pennate diatom species during long-term culture ». Acta Biologica Sibirica 6 (30 décembre 2020) : 669–78. http://dx.doi.org/10.3897/abs.6.e57888.

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The morphology of diatom siliceous is a primary basis for their species identification. This study aims to measure the range of morphological changes induced in the monoclonal cultures of Fragilaria radians strains 280 and A6 and Ulnaria danica strain BK17 by cultivation in the lab for a year or more. The scanning electron microscopy revealed that the number of abnormal valves increases during the first year of culture maintenance. Specific abnormalities observed include curved valves and apices, axial areas and rimoportulae shifted from their normal positions, disordered or otherwise abnormal striae, and various growths on the valves. Similar morphological abnormalities are known to occur in diatoms exposed to microtubule inhibitors. These results show the limits of morphological variance in studied species and could be used to estimate the effect of toxic agents in natural and experimental conditions.

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Aguilera, Victor M., Rubén Escribano et José Martínez-Oyanedel. « Electrophoretic protein profiles of mid-sized copepod Calanoides patagoniensis steadily fed bloom-forming diatoms ». Latin American Journal of Aquatic Research 43, n^o 4 (28 février 2017) : 798–806. http://dx.doi.org/10.3856/vol43-issue4-fulltext-20.

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Recent field and experimental evidence collected in the southern upwelling region off Concepción (36°5’S, 73°3’W) showed an abrupt reduction (<72 h) in the egg production rates (EPR) of copepods when they were fed steadily and solely with the local bloom-forming diatom Thalassiosira rotula. Because diatoms were biochemically similar to dinoflagellate Prorocentrum minimum, a diet which supported higher reproductive outcomes, the fecundity reduction observed in copepod females fed with the diatom may have obeyed to post-ingestive processes, giving rise to resources reallocation. This hypothesis was tested by comparing feeding (clearance and ingestion rates), reproduction (EPR and hatching success) and the structure of protein profiles (i.e., number and intensity of electrophoretic bands) of copepods (adults and eggs) incubated during 96 h with the two food conditions. The structure of protein profiles included molecular sizes that were calculated from the relative mobility of protein standards against the logarithm of their molecular sizes. After assessing the experimental conditions, feeding decreased over time for those females fed with T. rotula, while reproduction was higher in females fed with P. minimum. Electrophoretic profiles resulted similar mostly at a banding region of 100 to 89-kDa, while they showed partial differences around the region of 56-kDa band, especially in those females fed and eggs produced with T. rotula. Due to reproductive volume was impacted while larvae viability, a physiological processes with specific and high nutritional requirements, was independent on food type; post-ingestive processes, such as expression of stress-related proteins deviating resources to metabolic processes others than reproduction, are discussed under framework of nutritional-toxic mechanisms mediating copepod-diatoms relationships in productive upwelling areas.

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Kitchen, Sheila A., Andrea J. Bourdelais et Alison R. Taylor. « Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom ». PeerJ 6 (3 avril 2018) : e4533. http://dx.doi.org/10.7717/peerj.4533.

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Background The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na+) and calcium (Ca2+) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na+ VGCs. Methods We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na+/Ca2+ VGC of the non-toxic diatom Odontella sinensis using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin’s effect on voltage gated Na+/Ca2+ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na+/Ca2+ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na+ VGCs, previously identified as the PbTx binding site in animals. Results Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na+/Ca2+ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na+/Ca2+ VGCs than the 4-domain eukaryote channels. Discussion Although membrane excitability and the kinetics of action potential currents were unaffected, the permeation of the channels underlying the diatom action potential was significantly altered in the presence of PbTx-3. However, at environmentally relevant concentrations the effects of PbTx- on diatom voltage activated currents and interference of cell signaling through this pathway may be limited. The relative insensitivity of phytoplankton VGCs may be due to divergence of site-5 (the putative PbTx binding site), and in some cases, such as O. sinensis, resistance to toxin effects may be because of evolutionary loss of the 4-domain eukaryote channel, while retaining a single domain bacterial-like VGC that can substitute in the generation of fast action potentials.

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Wang, Jiayin, Liju Tan, Qi Li et Jiangtao Wang. « Toxic effects of nSiO2 and mPS on diatoms Nitzschia closterium f. minutissima ». Marine Environmental Research 193 (janvier 2024) : 106298. http://dx.doi.org/10.1016/j.marenvres.2023.106298.

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Stonik, Inna V., et Anton A. Zinov. « Changes in the Composition of Bloom-Forming Toxic Pseudo-nitzschia Diatoms in Surface Waters in Ussuri Bay, Northwestern Sea of Japan, during the Autumn Seasons of 2017–2022 ». Journal of Marine Science and Engineering 11, n^o 5 (11 mai 2023) : 1024. http://dx.doi.org/10.3390/jmse11051024.

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Diatoms of the genus Pseudo-nitzschia are producers of the neurotoxin domoic acid that causes serious damage to marine fauna and aquaculture farms. These microalgae are known as the most abundant group of toxic phytoplankton in Peter the Great Bay, Northwestern Sea of Japan, during the bloom season, which, as was previously reported for members of this group in the study region, lasts in the autumn months. Autumnal blooms of toxic diatoms Pseudo-nitzschia spp. were studied in the period from 2017 to 2022 in Ussuri Bay, the largest body of water in Peter the Great Bay, which harbors numerous recreational area and aquaculture farms. As a result, the following changes in the composition of bloom-forming species were recorded: blooms were caused by the Pseudo-nitzschia delicatissima group in the period from 2017 to 2020 and by P. multistriata in 2021–2022. An assumption has been made that one of the factors responsible for blooms of P. multistriata, known as one of the most widespread species in Asian warm-water areas, is an abnormally high water temperature in the autumn of 2021 in the study area.

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SAHIN, FATIH. « Structure and Dynamics of Phytoplankton Populations in the Black Sea from 2014 to 2017 ». Mediterranean Marine Science 25, n^o 3 (21 octobre 2024) : 682–97. http://dx.doi.org/10.12681/mms.37603.

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This study investigated the seasonal variations in phytoplankton communities along the Turkish Black Sea coast (2014-2017). Analyzing data from 20 stations revealed high biodiversity (175 species across 14 classes). Phytoplankton abundance showed distinct seasonality, with a peak in summer (2017, 96.6%) and lows in winter, characterized by dinoflagellate dominance. In terms of biomass, diatoms dominated in half of the sampling seasons, while dinoflagellates dominated in the other half at the surface during the study period. The dominance of dinoflagellates corresponded to the winters and summers of 2015 and 2016. The winter conditions of 2015 were harsh. The surface water community composition sometimes varied from that of the water column. Importantly, 44 potentially toxic species were identified, comprising 25% of the community and significantly contributing to both abundance (73.2-98.6%) and biomass (64-90.2%) throughout the year. These results highlight the unique structure of the Black Sea phytoplankton community, characterized by seasonal dominance of diatoms and a significant presence of potentially toxic species. Season, year, and water depth significantly influenced the phytoplankton assemblages. Water temperature was negatively correlated with dissolved oxygen and nitrogen-based nutrients.

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Sánchez-Marín, Paula, Vera I. Slaveykova et Ricardo Beiras. « Cu and Pb accumulation by the marine diatom Thalassiosira weissflogii in the presence of humic acids ». Environmental Chemistry 7, n^o 3 (2010) : 309. http://dx.doi.org/10.1071/en10015.

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Environmental context.Dissolved organic matter protects aquatic microorganisms from toxic metals by complexing and decreasing the concentration of the biologically reactive species such as free metal ions. However, there are some cases of enhancement of toxic effects when humic acids are present, which is thought to be due to effects of adsorbed humic acids on cell membranes. For a marine diatom, humic acids adsorbed to cell surfaces enhanced metal adsorption, whereas intracellular metal contents decreased as a result of metal binding by humic acids. These findings suggest that the diatom wall, the frustule, presents a barrier against direct effects of adsorbed humic acids on the plasma membrane. Abstract.Metal complexation by dissolved organic matter, as humic acids, is considered to decrease metal bioavailability by lowering the free metal ion concentration. However, dissolved organic matter adsorption on cell surfaces can modify cell membrane properties, which can also influence metal uptake. Copper and lead accumulation and internalisation by the marine diatom Thalassiosira weissflogii were studied in the absence and presence of humic acids, and adsorption of humic acids to cell surfaces was evaluated. Both Pb and Cu intracellular concentrations decreased in the presence of humic acids according to labile metal concentrations measured by anodic stripping voltammetry, whereas total (intracellular plus adsorbed) metal content was enhanced in the presence of humic acids, probably owing to enhanced metal plus humics adsorption to cell surfaces. The results of the present work stress the importance of differentiating between intracellular and total cellular metal in bioavailability studies, and suggest that the silica frustule of diatoms represents a barrier against humic acids effects on cell membranes.

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Varkitzi, Ioanna, Alexandra Pavlidou, Maria Pantazi, Eleni Rousselaki, Georgios-Angelos Hatiris, Eirini Gratsia, Vasilios Kapsimalis et Kalliopi Pagou. « Dumping of Dredge Spoil in the Pelagic Habitat : Focus on Trophic Status, Phytoplankton Diversity Responses and Generation of Blooms ». Water 14, n^o 15 (29 juillet 2022) : 2343. http://dx.doi.org/10.3390/w14152343.

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This study presents the impacts of dredge spoil dumping in the pelagic habitat during a 27-month monitoring survey in eastern Mediterranean coastal waters (Saronikos Gulf, Aegean Sea), with a focus on changes in trophic status and eutrophication levels, phytoplankton diversity and bloom dynamics. A number of environmental parameters and phytoplankton metrics were significantly influenced by the dumping operations, specifically phytoplankton diversity indices (number of species, Diatoms:Dinoflagellates ratio) and total abundance, Chlorophyll-a, light transmission, dissolved oxygen and inorganic nutrients, N:P ratio, and the Eutrophication Ιndex (a metric for trophic status assessment). Phosphates started to increase after the first year of dumping operations, shifting the N:P ratio to values lower than 10. A similarity cluster analysis highlighted that the phytoplankton community structure during the pre-dumping and the early-dumping period was clearly discriminated from the period during and after the dumping operations. A clear shift with an increase in the Diatoms:Dinoflagellates ratio was observed immediately after the initiation of dumping operations, which maximized in the dumping site after two years of operations. Diatoms dominated the phytoplankton communities, reaching ~ 95% relative abundance in the dumping site. High biomass producers or potentially toxic diatom species proliferated forming blooms. Pseudo-nitzschia multiseries was the most frequent potentially toxic species. A multivariate analysis (RDA) highlighted that among a suite of phytoplankton metrics plotted against stressors relevant to dumping, the Eutrophication Index, Chlorophyll-a, the diversity index Diatoms:Dinoflagellates ratio and the abundance of the potentially toxic diatom P. multiseries emerged as the most suitable to reflect the responses of phytoplankton communities to dumping. Dredge spoil dumping at sea poses pressures to ecosystem components addressed by the European Marine Strategy Framework Directive (MSFD) monitoring programs. In such a context, this study further supports the role of phytoplankton diversity and blooms as sensitive monitoring elements for the environmental status assessment and dumping management in coastal waters.

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Ehrman, James M., et Irena Kaczmarska. « A VIRTUAL INSTRUMENT METAPHOR FOR OBJECT IDENTIFICATION : AN EXAMPLE APPLICATION USING TOXIC DIATOMS ». Limnology and Oceanography Bulletin 13, n^o 1 (mars 2004) : 1–4. http://dx.doi.org/10.1002/lob.20041311.

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Stelmakh, Liudmila V., Irina M. Mansurova, Tatiana L. Gorbunova et Olga S. Alatartseva. « Toxicity effects of copper on two species of marine diatoms microalgae and two species of dinoflagellates ». Ecologica Montenegrina 58 (27 octobre 2022) : 55–68. http://dx.doi.org/10.37828/em.2022.58.6.

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The copper toxic effect was studied on two species of Black Sea diatoms Cerataulina pelagica and Phaeodactylum tricornutum, and two species of dinoflagellates Levanderina fissa and Prorocentrum nanum. A wide range of variability in the resistance of cultures to copper as a toxicant is demonstrated. The EC50 values for different species varied from 1.8 to 43.7 mg·L-1. An increase in the algae initial biomass within one species caused a corresponding decrease in the toxic effects of Cu2+. The two species of dinoflagellates with similar initial biomass and practically equal values of the specific growth rate, demonstrated significant difference in the EC50 parameter. In the small - celled species P. nanum it was equal to 43.7 mg·L-1, whereas, in the large species L. fissa, it decreased by almost 10 times. In the small-cell strain of the diatom C. pelagica, the semi-inhibition growth parameter was 13.5 mg·L-1, which is 2.4 times higher than in the large-cell strain with all other conditions being equal. The copper toxicological effect at low concentrations is determined, first of all, by a decrease in the electronic transport rate values (rETR) in cultures. The second parameter in terms of sensitivity to copper is Fv/Fm (maximum efficiency of photosystem II). The algae morphometric parameters are the most resistant to its impact: the volume and cell’s surface area, as well as the specific surface area. The significant changes on the third day of experiments were observed most often, at a copper concentration near EC50 or above.

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González-Paz, Lorena, Josué Gestido, Cristina Delgado, Nuria Pedrol et Isabel Pardo. « Short-Term Effect of Eucalyptus Leachates on Green Food Webs in Headwaters ». Water 15, n^o 1 (29 décembre 2022) : 115. http://dx.doi.org/10.3390/w15010115.

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Despite the reported allelopathic nature of the Eucalyptus genus, eucalypt leachates have unknown effects on the trophic base of stream green food webs. Eucalypt plantations have increased worldwide, including riparian ecosystems. We aimed to test whether short-term eucalypt leachates might alter water chemistry, periphytic algal biomass and diatoms, and herbivorous invertebrates’ (i.e., scrapers). We studied two oligotrophic and well-preserved headwaters from NW Spain. The experiment followed a before-after control-impact paired (BACIp) design, with weekly sampling before and after eucalypt leaves addition to streams. In the stream with lower discharge, the eucalypt treatments seemed to affect increases in biomass accrual (Chl-a) and diatom assemblages, disfavouring sensitive species (e.g., Eunotia minor and Achnanthidium pyrenaicum). Therefore, the ecological status was reduced from high to good. In the stream with higher discharge, invertebrate assemblages changed with scrapers having their abundances modified in comparison with the control (e.g., Habrophlebia sp. and Elmidae). Results suggest that eucalypt leaves leachates exert toxic effects on periphyton and on diatom and invertebrate assemblages, and this effect might be mediated by discharge. Alterations at the base of stream food webs may compromise their good ecological status. Further studies are necessary to identify whether this toxicity is due to allelopathic processes.

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Trimborn, Scarlett, Nina Lundholm, Silke Thoms, Klaus-Uwe Richter, Bernd Krock, Per Juel Hansen et Björn Rost. « Inorganic carbon acquisition in potentially toxic and non-toxic diatoms : the effect of pH-induced changes in seawater carbonate chemistry ». Physiologia Plantarum 133, n^o 1 (mai 2008) : 92–105. http://dx.doi.org/10.1111/j.1399-3054.2007.01038.x.

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Cabrera, Joaquin, Susana Puntarulo et Paula Mariela González. « Domoic Acid Oxidative Effects on the Microalgae Phaeodactylum tricornutum ». Life 13, n^o 3 (2 mars 2023) : 676. http://dx.doi.org/10.3390/life13030676.

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Domoic acid (DA) is a natural occurring marine biotoxin. Oxidative stress generation due to DA exposure was reported in animals, but little is known on the phytoplankton community. The aim of this work was to verify whether exposure to DA in the marine diatom Phaeodactylum tricornutum favors reactive oxygen species (ROS) generation in the intracellular environment modifying its antioxidant capacity. Active species production, non-enzymatic antioxidant content, and antioxidant enzyme activities over the three growth phases of P. tricornutum exposed to 64 µM DA were evaluated. Results obtained in exponential growing cells showed a time-depending seven-fold increase in the 2′,7′ dichlorofluorescein diacetate dye oxidation rate. Superoxide dismutase and catalase activities showed a two-fold increase, and glutathione related enzymes activities were also significantly increased in treated diatoms as compared to controls. However, glutathione and ascorbate contents significantly decreased after incubation of the cells with DA. Similar effects were observed in latent and stationary phases of cell development. These results showed that DA could cause a severe oxidant-dependent impact on a non-toxic algae.

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