Search

Monodominant (one species dominates) or polidominant (multiple species dominate) cyanobacterial blooms are pronounced in productive freshwater ecosystems and pose a potential threat to the biota due to the synthesis of toxins. Seasonal changes in cyanobacteria species and cyanometabolites composition were studied in two shallow temperate eutrophic lakes. Data on cyanobacteria biomass and diversity of dominant species in the lakes were combined with chemical and molecular analyses of fifteen potentially toxin-producing cyanobacteria species (248 isolates from the lakes). Anatoxin-a, saxitoxin, microcystins and other non-ribosomal peptides formed the diverse profiles in monodominant (Planktothrix agardhii) and polidominant (Aphanizomenon gracile, Limnothrix spp. and Planktolyngbya limnetica) lakes. However, the harmfulness of the blooms depended on the ability of the dominant species to synthesize cyanometabolites. It was confirmed that P. agardhii produced a greater amount and diverse range of MCs and other NRPs. In the polidominant lake, isolates of the co-dominant A. gracile, L. planctonica and P. limnetica synthesized no or only small amounts of cyanometabolites. In general, the profile of cyanometabolites was greater in cyanobacteria isolates than in environmental samples, indicating a high potential for toxic cyanobacteria bloom.

Cyanobacteria are a bloom-forming ancient group of photosynthetic prokaryotes. A rise in temperature is a major contributor to its massive proliferation, namely on freshwater ecosystems, with social and economic impacts. Thus, reliable and cost-effective tools can permit the fast surveillance and assessment of temperature effects on potentially toxic cyanobacteria distribution and impacts. The occurrence of three potentially toxic cyanobacteria species was assessed on seven sampling points across three sampling years. Moreover, the association between the occurrence of those cyanobacteria species with climate change events was addressed. Here, we combined molecular and statistical methods to study the impacts of temperature on the occurrence of three globally occurring cyanotoxin-producing cyanobacteria species—Microcystis aeruginosa (microcystins), Raphidiopsis raciborskii (cylindrospermopsins and saxitoxins) and Planktothrix agardhii (microcystins and saxitoxins). Samples were collected on seven European temperate freshwater systems located on the North and Centre regions of Portugal, across three distinct sampling years with distinct ranges of air temperature. Data support that M. aeruginosa is still a common inhabitant of Portuguese freshwater ecosystems and a new trend was found on R. raciborskii recent invasion and establishment on the colder north ecosystems of Portugal. Additionally, the highest frequency of detection of both cyanobacteria was associated with warmer years. P. agardhii also revealed a new trend, being reported for the first time on North and Centre Regions of Portugal, however with no statistical relation with air temperature, demonstrating a higher ecological fitness. Distinct profiles of the statistical analysis on the three tested cyanobacteria species contribute to deepen the studies on other species as well as of our analyzed species on a global level. This assessment may help to anticipate possible repercussions on water quality and public health due to most probable alterations on cyanotoxins profile given the ecological fitness established among air temperature and PCR detection of potentially toxic cyanobacteria.

The removal of endocrine-disrupting xenobiotics, technical nonylphenol (NP) and 4-tert-octylphenol (OP), from aquatic environment by the cyanobacterium Planktothrix agardhii has been studied. It is shown that nonyl- and octylphenols are removed from aqueous medium in the presence of the cyanobacterium P. agardhii mainly via abiotic pathways—photolysis and hydrolysis—and biodegradation by cyanobacterial cells rather than by adsorption and accumulation in the cells. P. agardhii has a higher destructive and sorption ability for nonylphenol compared to octylphenol. The results indicate the possibility of self-purification of water bodies contaminated with alkylphenols with the participation of the mass species of cyanobacteria Planktothrix agardhii.

Actually, harmful cyanobacterial efflorescence in Algerian water bodies used for drinking water are dominant throughout the year and their management requires a better knowledge of the cyanobacteria dynamics and the environmental parameters related to their dominance. The Ain Zada reservoir is a home of 5 genera. Occurrence frequency estimation of the identified genera shows the constancy of Planktothrix, the regularity of Aphanizomenon, Pseudanabaena and Cylindrospermopsis and the rarity of Oscillatoria. The dominating genus Planktothrix is represented exclusively by Planktothrix agardhii ; This species showed the highest proportion rates in winter (95.61 %), spring (94.80 %) and autumn (80.29 %) and the lowest in summer (29.16 %). Planktothrix agardii abundances show positive relation with suspended solids and chlorophyll a and negative relation with the depth of Secchi disc. Blooms of the potential toxinogenic Planktothrix agardhii and Cylindrospermopsis are related negatively. Results from cyanotoxins and pigments characterization showed a strong positive relation of Planktothrix agardhii abundance with microcystins (MCs) and phycocyanin (PC) concentrations. Indeed, in Ain Zada dam, we found that MCs contents have positive relation with water temperature and pH and negative relation with NO3. Our results show that, except for the months of March, October and November, the monthly abundances of cyanobacterial population recorded in Ain Zada dam exceeded the alert level 2. The filamentous species found in this dam are of great concern they are able to synthesize toxins harmful to aquatic and terrestrial organisms. Further research is needed to confirm the presence of other cyanotoxins (e.g. cylindrospermopsin) in Ain Zada dam.

Cyanobacteria are a group of microorganisms that can be found in a diverse range of biogeographical areas and produce potent and damaging cyanotoxins, which reveal importance for continuous studies and surveillance efforts. In this study, we analyzed worldwide two-month culture-enriched water samples collected from 12 distinct countries (Costa Rica, Cuba, Fiji, France, Indonesia, Mali, Portugal, South Africa, Spain, Thailand, USA, Vietnam) including two undisclosed areas (Fiji and Mali). We performed a PCR-based molecular multi-step scheme that consisted in the detection of the main cyanobacterial species, genera, and cyanotoxins biosynthesis genes. Results from this study indicate that Microcystis aeruginosa followed by Planktothrix agardhii were the most prevalent species of all the 12 countries analyzed. Cylindrospermospis raciborskii was detected in Costa Rica, while P. agardhii was detected in Fiji and South Africa. M. aeruginosa was detected in Fiji and Mali. Regarding the main cyanotoxins biosynthesis genes, a cyrC gene fragment (cylindrospermopsins) was amplified in the African continent (South Africa), while anaC (anatoxin-a) was detected in two distinct locations, Mali and Vietnam. Saxitoxins biosynthesis gene was also detected in Fiji and Vietnam. Microcystins biosynthesis gene (mcyA) was co-detected with anatoxin-a biosynthesis gene in Mali and with saxitoxins biosynthesis gene (sxtI) in Portugal. This study therefore constitutes a major contribution to the global biogeography of cyanobacteria and its cyanotoxins and recommends continuous vigilance of toxic cyanobacteria particularly in the more undisclosed areas of the world. The PCR analysis data obtained in our 2-month culture-enriched water samples supports molecular methods as a preliminary tool in the environmental surveillance of cyanobacteria and cyanotoxins in undisclosed locations, particularly since the several positive amplifications detected may indicate that though samples were collected under non-bloom conditions, if environmental conditions change in the ecosystem, there is a risk that bloom-forming species may arose along with their detected cyanotoxicity.

Winter cyanobacterial blooms have become increasingly common in eutrophic lakes advocating a need for their monitoring and risk assessment. The present study evaluated the toxicity of a winter cyanobacterial bloom in a eutrophicated freshwater lake located in Western Poland. The bloom was dominated by potentially toxic species: Planktothrix agardhii, Limnothrix redekei, and Aphanizomenon gracile. The toxin analysis revealed the presence of demethylated forms of microcystin-RR and microcystin-LR in ranges of 24.6-28.7 and 6.6-7.6 µg/L, respectively. The toxicity of sampled water was further evaluated in platelet-rich plasma isolated from healthy human subjects using lipid peroxidation and lactate dehydrogenase assays. No significant adverse effects were observed. The present study demonstrates that toxicity of some winter cyanobacterial blooms in the temperate zone, like that in Lubosińskie Lake, may not exhibit significant health risks despite microcystin production.

The occurrence of cyanobacteria in freshwaters attracts much attention due to its associated health threats and ecological implications. Yet data on the composition of cyanobacteria taxa and toxigenicity in some regions is still scarce. Here, we explored the occurrence of cyanobacteria and cyanotoxins in three locations in Ukraine (reservoir for Kasperivtsi Hydrothermal Power Plant and outflowing River Seret, and cooling pond of Khmelnytsky Atomic Power Plant) in summer 2017. Cyanobacteria were a dominant fraction at all stations. A number of potent-toxin producers were identified including Cylindrospermopsis raciborskii, Aphanizomenon gracile, Dolichospermum flos-aquae, and Planktothrix agardhii. Screening for the presence of dissolved and particulate content of microcystins (-LR, -YR, and -RR), cylindrospermopsin, and anatoxin-a yielded negative results. The studied waters displayed no toxicity in human platelets in vitro. Further toxicological and ecological studies are necessary to evaluate the potential presence of cyanotoxin producers in Ukraine.

Dinámica de un florecimiento algal otoñal en un lago hipereutrófico urbano de la región pampeana semiárida (Argentina). En este trabajo, se reporta un raro florecimiento fitoplanctónico otoñal en un lago somero de la región semiárida pampeana (Argentina). La biomasa fitoplanctónica presentó un solo pico otoñal, seguido dos meses más tarde por un pico en la clorofila. El pico de biomasa coincidió con un débil pastoreo sobre la comunidad fitoplanctónica (dominada por la poco pastoreada Planktothrix agardhii (Gomont) Anagnostidis et Komárek) junto con una reducción de la limitación por N en el otoño. El pico de clorofila ocurrió cuando las algas aumentaron su contenido de clorofila probablemente debido a la reducción de la radiación solar y la baja transparencia del agua. Esto indicará que la estacionalidad del fitoplancton en esta área particular depende de múltiples factores bióticos y abióticos. In this paper we report a rare autumm phytoplankton bloom in a shallow lake of the semiarid Pampean area of Argentina. Phytoplankton biomass peaked only once during the autumn, followed 2 months later by a chlorophyll peak. The biomass peak might have been the result of a weak grazing pressure on the phytoplankton community (dominated by the nongrazeable Planktothrix agardhii (Gomont) Anagnostidis et Komárek) coupled with a reduction in the N-limitation towards the autumm. The chlorophyll peak took place when phytoplankton cells increased their chlorophyll content probably due to a reduction of solar irradiance and low water transparency. This findings indicate that phytoplankton seasonality in this particular area may depend on multiple biotic and abiotic factors.

Harmful cyanobacteria and their cyanotoxins may contaminate drinking water resources and their effective control remains challenging. The present study reports on cyanobacterial blooms and associated cyanotoxins in the Obrzyca River, a source of drinking water in Poland. The river was examined from July to October 2019 and concentrations of microcystins, anatoxin-a, and cylindrospermopsin were monitored. The toxicity of water samples was also tested using an ecotoxicological assay. All studied cyanotoxins were detected with microcystins revealing the highest levels. Maximal microcystin concentrations (3.97 &mu, g/L) were determined in September at Uście point, exceeding the provisional guideline. Extracts from Uście point, where the dominant species were Dolichospermum flos-aquae (August), Microcystis aeruginosa (September), and Planktothrix agardhii (October), were toxic for Dugesia tigrina Girard. Microcystin concentrations (MC-LR and MC-RR) were positively correlated with cyanobacteria biovolume. Analysis of the chemical indicators of water quality has shown relationships between them and microcystins as well as cyanobacteria abundance.

Molecular studies on cyanobacteria often involve filtering and freezing of samples leading to loss of cell morphological features. Methanol is often used in preservation of biological materials in association with other fixatives. This study evaluates the application of methanol in the preservation of DNA for molecular studies as well as for the preservation of cell morphology for morphometric analysis in filamentous cyanobacteria. In the present study, both culture and environmental bloom samples were preserved using a cold methanol dehydration series (50, 70, and 100 %) and stored at −20 °C for up to 2 years. The DNA quantity and quality, nucleotide sequence retrieval, and real-time PCR quantification were analyzed over time. Morphometric cell analysis was performed on preserved samples. Results show that the DNA extracted from samples preserved up to 6 months was successfully quantified by real-time PCR. After that period, the DNA quantity decreased with the preservation time. Nevertheless, we were able to detect/amplify the target fragment in samples preserved up to 2 years. The DNA sequence and cell morphology were also maintained during the preservation time. Thus, methanol preservation is an adequate method to preserve molecular information and morphological features after long storage periods. © 2015, Springer Science+Business Media Dordrecht. This research was partially supported by the European Regional Development Fund (ERDF) through the COMPETE - Operational Competitiveness Program - and FCT - Foundation for Science and Technology national funds through projects PPCDT/AMB/67075/2006 and PEst-C/MAR/LA0015/2013, the Post-Doc research grant SFRH/BPD/75922/2011 to E. Valério and Ph.D. research grant SFRH/BD65706/2009 to C. Churro. The authors acknowledge S. Paulino from the Laboratory of Biology and Ecotoxicology of the National Institute of Health Doutor Ricardo Jorge for the assistance in the biovolume measurements.

Aim: The present study aimed to investigate the composition and toxicity of the phytoplankton in Sítios Novos reservoir, used mainly as drinking water supply for approximately 30,000 people.MethodsSamples were collected between January 2010 and June 2011.ResultsDuring this period 19 taxa of cyanobacteria and 22 of algae were identified. Out of 45 samples collected, algae accounted for no more than 10% of the quantified organisms in 44 samples. Cyanobacteria accounted for 100% of the organisms quantified in three samples and for 99% in other 29 samples. Among the cyanobacteria group, Planktothrix agardhii (Gomont) Anagnostidis & Komárek and Cylindrospermopsis raciborskii (Woloszynska) Seenaya & Subbaraju prevailed and both strains were isolated and identified as paralytic shellfish poison (PSP) producers. C. raciborskii strain has shown to produce SXT and dcSXT while P. agardhii strain has shown to produce dcGTX2 or 3.ConclusionsTo the author’s knowledge, this is the first report of PSP-producer cyanobacteria species isolated in Northeastern Brazil and the first reported of a P. agardhii synthesizing dcGTX2/3.

A resistência de bactérias patogénicas à antibioterapia é um dos principais problemas de saúde pública, face à crescente ineficácia dos antibióticos no tratamento de doenças infeciosas. Assim, a pesquisa de novos antibióticos é um importante desafio da investigação em saúde. O potencial farmacológico de cianobactérias tem sido avaliado e descrito, mas, no entanto, ainda não há nenhum composto cianobacteriano que tenha sido aprovado pelas autoridades do medicamento como agente antibacteriano. Neste trabalho avaliámos a atividade de extratos de 40 estirpes de Planktothrix agardhii contra duas bactérias patogénicas: Klebsiella pneumonia e Staphylococus aureus. Para cada espécie bacteriana alvo usou-se uma estirpe de referência (ATCC) e uma estirpe clínica, isolada a partir de amostras de pacientes e estudadas no Laboratório de Resistência aos Antibióticos e Infeções Associadas aos Cuidados de Saúde. As estirpes de P. agardhii foram isoladas de albufeiras portuguesas e têm sido mantidas na coleção “Estela Sousa e Silva Algae Culture Collection” do Laboratório de Biologia e Ecotoxicologia. A biomassa de P. agardhii (200mg) foi extraída com metanol (70%, 10mL/100mg) overnight e sujeita a ciclos de sonicação. O metanol dos extratos foi evaporado e os extratos aquosos resultantes foram purificados em cartuchos C18. A atividade dos extratos contra as bactérias K. pneumonia e S.aureus foi avaliada através do método da Difusão em Disco (EUCAST), usando discos impregnados com 2, 4, 6, 8 e 10 mg de cada extrato. De acordo com os resultados preliminares, nenhum dos extratos apresenta atividade contra K. pneumonia, mas o extrato de P. agardhii LMECYA 256 apresenta um ligeiro halo de inibição relativamente às estirpes de S. aureus, de uma forma aparentemente dependente da dose de extrato aplicada. O S. aureus é uma bacteria Gram-positiva, frequentemente associada a uma vasta gama de patologias, desde simples infeções na pele, até infeções graves como pneumonia e meningite. Assim, revela-se do maior interesse explorar as propriedades antibacterianas de cianobactérias, designadamente do género Planktothrix, contribuindo, desta forma, para um dos desafios atuais da ciência: a identificação de novos antibióticos de origem natural. FCT N/A

Cyanobacteria are phytoplanktonic organisms widely occurring in freshwaters, being frequently associated with the production of toxins, especially microcystins (MCs). MCs are produced non-ribosomally by a multienzyme complex (mcy genes). It has been reported that environmental factors, such as light intensity, can influence toxin production. The aim of this study was to assess the influence of light intensity in the transcription of the mcyA gene and corresponding production of microcystins in toxic isolates of Planktothrix agardhii, where little is known, and compare them to Microcystis aeruginosa. COMPETE; FCT N/A

Based on current structural and statistical calculations, thousands of microcystins (MCs) can exist, yet, to date, only 246 MCs were identified and only 12 commercial MC standards are available. Standard mass spectrometry workflows for known and unknown MCs need to be developed and validated for basic and applied harmful algal bloom research to advance. Our investigation focuses on samples taken in the spring of 2018 from an impoundment fed by Oser and Bischoff Reservoirs, Indiana, United States of America (USA). The dominant cyanobacterium found during sampling was Planktothrix agardhii. The goal of our study was to identify and quantify the MCs in the impoundment sample using chemical derivatization and mass spectrometry. Modifying these techniques to use online concentration liquid chromatography tandem mass spectrometry (LC&ndash, MS/MS), two untargeted MCs have been identified, [d-Asp3, Dhb7]-MC-LR and [Dhb7]-MC-YR. [Dhb7]-MC-YR is not yet reported in the literature to date, and this was the first reported incidence of Dhb MCs in the United States. Furthermore, it was discovered that the commercially available [d-Asp3]-MC-RR standard was [d-Asp3, Dhb7]-MC-RR. This study highlights a workflow utilizing online concentration LC&ndash, MS/MS, high-resolution MS (HRMS), and chemical derivatization to identify isobaric MCs.

Las cianobacterias son organismos procariotas, capaces de efectuar fotosíntesis con liberación de O2, que forman parte del fitoplancton de todos los tipos de cuerpos de agua continentales. Algunas especies producen "floraciones algales" que son proliferaciones masivas, relativamente repentinas y espacialmente restringidas, protagonizadas por una o pocas especies, que dominan el fitoplancton. Las floraciones de cianobacterias son nocivas porque intervienen especies capaces de sintetizar cianotoxinas y metabolitos volátiles. Consecuentemente, representan un serio problema ecológico, económico y sanitario. Para asegurar la calidad de los recursos hídricos destinados al consumo o la recreación, es necesario poder identificar las especies de cianobacterias presentes así como su capacidad de producir toxinas. Asimismo, es de vital importancia comprender los factores que promueven la dominancia en sistemas eutróficos.En este trabajo de tesis se analizó, en primer lugar, la distribución geográfica de las floraciones de cianobacterias y sus toxinas en los cuerpos de agua continentales de Argentina. Por otro lado, se dieron a conocer los taxa de cianobacterias planctónicas presentes en la laguna somera Los Patos, (Ensenada, Provincia de Buenos Aires) y se estudió la influencia de los factores ambientales sobre la dinámica del fitoplancton dominado por cianobacterias filamentosas. Se realizó además, el aislamiento de dos cepas nativas de Raphidiopsis mediterranea y una de Planktothrix agardhii, provenientes de muestras ambientales de dos lagunas someras de la Provincia de Buenos Aires (laguna Los Patos y de los Padres) y su caracterización ultraestructural, molecular y toxicológica, mediante análisis polifásicos. Asimismo, se estudió el efecto de dos intensidades lumínicas y de dos concentraciones de fosfato sobre las densidades y la morfología de poblaciones de R. mediterranea y P. agardhii creciendo en co-cultivo. Adicionalmente, se analizó la respuesta de cultivos monoalgales de R. mediterranea y P. agardhii aisladas de Los Patos, ante condiciones de deficiencia de fosfato. Por último, utilizando ensayos de laboratorio, se evaluó el efecto de la adición de nutrientes y de dos intensidades lumínicas sobre la estructura, cambios morfológicos y crecimiento de una comunidad fitoplanctónica, dominada por cianobacterias filamentosas no heterocísticas, tomada del lago Javier (Canelones, Uruguay).Los resultados de este trabajo indican que las floraciones nocivas de cianobacterias se localizan a lo largo y ancho de nuestro país, desarrollándose en cuerpos de agua lóticos y lénticos, siendo Microcystis, y en menor medida Dolichospermum, Raphidiopsis, Cylindrospermopsis y Planktothrix, los géneros más frecuentes. Las concentraciones de microcistinas en cuerpos de agua utilizados como fuente de agua de consumo y recreación, en muchas ocasiones, superan los límites sugeridos por la Organización Mundial de la Salud. Los resultados de los experimentos con comunidades naturales provenientes del lago Javier, indicaron que la interacción entre los nutrientes y la intensidad lumínica promueve cambios en la dominancia de las cianobacterias filamentosas. Las especies Cylindrospermopsis raciborskii and Aphanizomenon aff. gracile del Orden Nostocales presentaron una plasticidad fenotípica mayor que los taxa filamentosos no heterocísticos del Orden Oscilatoriales y Synechoccocales. Estos resultados ayudan a entender las condiciones ambientales que pueden determinar la dominancia de las Nostocales.El fitoplancton de la laguna Los Patos se caracterizó por la presencia de floraciones de P. agardhii, las cuales se alternaron con floraciones de especies Nostocales, en particular R. mediterranea. La temperatura, la disponibilidad de luz y de nutrientes fueron los factores principales que determinaron la alternancia y la dominancia P. agardhii y R. mediterranea. La información obtenida a partir de los experimentos con cultivos mixtos y monoalgales resultó de utilidad para interpretar los patrones de alternancia y dominancia observados en la laguna Los Patos. Estos ensayos aportaron información sobre cómo los caracteres eco-fisiológicos pueden explicar la coexistencia de las cianobacterias filamentosas formadoras de floraciones. En particular, permitieron demostrar que R. mediterranea presenta cierto grado de plasticidad fenotípica y flexibilidad fisiológica en relación con la luz y la asimilación de fósforo, lo que podría explicar, en parte, la co-existencia bajo la dominancia de P. agardhii. Por último, los caracteres morfológicos, moleculares y ultraestucturales fueron congruentes entre sí en cuanto a la asignación de una de las cepas a la especie P. agardhii. Por otro lado, las filogenias construidas en base a secuencias de distintos marcadores moleculares revelaron que las cepas de C. raciborskii y Raphidiopsis (R. mediterranea, R. curvata y R. brookii) conforman un grupo con altos valores de soporte estadístico. La posición en los árboles filogenéticos (siempre juntas) podría deberse a una divergencia reciente de las especies (o cepas o ecotipos) y sugiere, además, que la emergencia del carácter autapomórfico que define a Raphidiopsis (ausencia de heterocistos) podría ser la consecuencia de eventos independientes. El presente estudio es una contribución a la elucidación de la clasificación taxonómica de los géneros Raphidiopsis y Cylindrospermopsis dado que complementa trabajos previos y da lugar a nuevos interrogantes sobre el estatus de los mismos. Fil: Aguilera, Anabella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina. Autor

Cyanobacteria blooms are frequent in freshwaters and are responsible for water quality deterioration and human intoxication. Although, not a new phenomenon, concern exists on the increasing persistence, scale, and toxicity of these blooms. There is evidence, in recent years, of the transfer of these toxins from inland to marine waters through freshwater outflow. However, the true impact of these blooms in marine habitats has been overlooked. In the present work, we describe the detection of Planktothrix agardhii, which is a common microcystin producer, in the Portuguese marine coastal waters nearby a river outfall in an area used for shellfish harvesting and recreational activities. P. agardhii was first observed in November of 2016 in seawater samples that are in the scope of the national shellfish monitoring system. This occurrence was followed closely between November and December of 2016 by a weekly sampling of mussels and water from the sea pier and adjacent river mouth with salinity ranging from 35 to 3. High cell densities were found in the water from both sea pier and river outfall, reaching concentrations of 4,960,608 cells·L−1 and 6810.3 × 106 cells·L−1 respectively. Cultures were also established with success from the environment and microplate salinity growth assays showed that the isolates grew at salinity 10. HPLC-PDA analysis of total microcystin content in mussel tissue, water biomass, and P. agardhii cultures did not retrieve a positive result. In addition, microcystin related genes were not detected in the water nor cultures. So, the P. agardhii present in the environment was probably a non-toxic strain. This is, to our knowledge, the first report on a P. agardhii bloom reaching the sea and points to the relevance to also monitoring freshwater harmful phytoplankton and related toxins in seafood harvesting and recreational coastal areas, particularly under the influence of river plumes. © 2017 by the authors. Licensee MDPI, Basel, Switzerland. Acknowledgments: This work was supported by the project SNMB—INOV: Innovation for a more competitive shellfish sector co-financed by the Portuguese Government, Operational Program (OP) Mar 2020, Portugal 2020 and European Union through the European Structural Funds and Investment Funds (FEEI) and European Maritime and Fisheries Fund (EMFF). The authors also acknowledge the Centre of Marine Sciences (CCMAR), University of Algarve and Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) of the University of Porto and the Funding of RD Units Strategic Plan from the Portuguese Foundation for Science and Technology (FCT) through the projects UID/Multi/04326/2013 and UID/Multi/04423/2013 respectively.

Comparative data analysis for phytoplankton of the Pregolya River and small rivers of the Pregolya River Basin in the late 1990s and in 2000s shows great influence of the Angrapa River water on the structure of phytoplankton of the Pregolya River compared to the Instruch River. Presumably, cyanobacterium Planktothrix agardhii is imported to the Pregolya River and further to the Curonian Lagoon via the Deima River from the Masurian Lakes in Poland, where the species has been one of the summer phytoplankton dominants since the 2000s. Information on the structure and quantitative development of phytoplankton of the Pregolya tributaries of the second and third order was obtained for the first time.

Cyanobacteria are phytoplanktonic organisms widely occurring in freshwaters, being frequently associated with the production of toxins, namely microcystins (MCs). MCs are produced non-ribosomally by a multienzyme complex (mcy genes). It has been reported that environmental factors, such as light intensity, can influence toxin production. The aim of this study was to assess the influence of light intensity in the transcription of the mcyA gene and corresponding production of microcystins in toxic isolates of Planktothrix agardhii, where little is known, and compare them to Microcystis aeruginosa. For that purpose, cultures were exposed to three different light intensities (4, 20 and 30 μmol photons m-2 s-1) for 18 days at 20 ± 1 °C. The growth was followed daily using absorbance readings. Samples were collected at each growth stage for cell counting, microcystins quantification and RNA extraction. The level of transcripts was quantified by RT-qPCR and the relative expression determined using 16S rDNA, gltA and rpoC1 as reference genes. The most stable reference genes in M. aeruginosa were rpoC1 and gltA, whereas in P. agardhii were 16S rDNA and gltA. There was a correspondence between the growth rate and light intensity in M. aeruginosa and P. agardhii. The growth rates for both species were lower at 4 and higher at 30 μmol photons m-2 s-1. Microcystin concentration per cell was similar between light intensities in M. aeruginosa and over time, while in P. agardhii it was higher in the stationary phase at 4 μmol photons m-2 s-1. There were differences in the expression of mcyA between the two species. In M. aeruginosa, the highest levels of expression occurred at 4 μmol photons m-2 s-1 in the adaptation phase, whereas for P. agardhii it was at 4 μmol photons m-2 s-1 in the exponential growth phase. Our results indicate that the light intensities tested had distinct influences on the growth, microcystin production and mcyA expression levels, presenting considerable differences in M. aeruginosa and P. agardhii. © 2016 Elsevier This research was partially supported by the European Regional Development Fund (ERDF) through the COMPETE – Operational Competitiveness Program – and FCT — Foundation for Science and Technology national funds through Ph.D research grant SFRH/BD65706/2009 to C. Churro and Post-Doc research grant SFRH/BPD/75922/2011 to E. Valério. The authors thank Sérgio Paulino for the assistance in the microcystins quantifications with ELISA kit and Carina Menezes for the HPLC evaluations.

International audience; Planktothrix agardhii (P. agardhii), a filamentous cyanobacterium commonly found in freshwater environments, has also been reported in brackish areas. In order to test the hypothesis of an acclimation of P. agardhii to its environmental salinity, we monitored growth and morphometry of P. agardhii brackish and freshwater strains under various salinities (0 to 15 psu). Despite differences in their response under increasing salinities (0–15 psu), the brackish strains show: (i) growth less gradually inhibited by increasing salinities than the freshwater strains; (ii) growth nearly optimal in the salinity of their natural environment (iii) a salt tolerance range wider (0 to [12.5–15 psu]) than that of freshwater P. agardhii (0 to [7.5–10 psu]). Our findings suggest that this tolerance may be due to an acclimation of the strains to their environment by effective salt extrusion and compatible solutes accumulation. This salt acclimation, just as the population response to various salinities, is well reflected by the filaments morphometry. This study highlights the ability of potentially harmful cyanobacteria to acclimate to salinity in a salinization context.

International audience; Natural leaf litter inputs is one factor that may help to minimize the likelihood of excessive algal growth. We tested the allelopathic effect of the grey willow (Salix atronicerea) on two phytoplankton species: Planktothrix agardhii (toxic and non-toxic cyanobacterial strains) and Scenedesmus communis (a chlorophyte). Effect was evaluated by combining leaf extracts and pulse amplitude modulation (PAM) chlorophyll fluorescence yield to measure photosynthetic activity responses. Phototrophic growth of the cyanobacterial species was suppressed even at very low concentrations of the extract while growth of the chlorophyte species was not affected. In the two cyanobacteria strains, inhibition of the chlorophyll fluorescence yields was significantly higher in the microcystin-free strain. Polyphenols are suspected to cause oxidative damage to cyanobacteria and thereby induce selective growth inhibition, similarly to hydrogen peroxide treatments against harmful cyanobacteria. Our results evidence willow extract or exudate as a promising agent selectively affecting cyanobacterial growth, but further studies are needed to determine the environmental impact and the inhibiting process. © 2016 Elsevier B.V.

As cianobactérias são frequentemente associadas à produção de toxinas, nomeadamente microcistinas. A sua síntese é não ribossomal, e acontece utilizando complexos multienzimáticos (genes mcy). Diversos estudos têm demonstrado que os fatores ambientais podem influenciar a produção de toxina. O objetivo deste estudo foi avaliar a influência da intensidade da luz na transcrição do gene mcyA e correspondente produção de microcistina em isolados tóxicos de Microcystis aeruginosa e Planktothrix agardhii. Para esse fim, as culturas foram expostas a três diferentes intensidades de luz (4, 20 e 30 µmol fotões m-2 s-1) durante 18 dias a 20 ± 1ºC. O crescimento foi seguido diariamente espectrofotometricamente. O nível de transcritos foi quantificado por RT-qPCR e a expressão relativa determinada usando três genes de referência - rRNA 16S, gltA e rpoc1. Os resultados mostraram a existência de uma correspondência entre a taxa de crescimento e a intensidade de luz em ambas as espécies. As taxas de crescimento foram menores a 4 e maiores a 30 µmol fotões m-2 s-1. Em M. aeruginosa a concentração de microcistina por célula foi semelhante entre intensidades de luz e ao longo do tempo, enquanto que em P. agardhii a concentração foi mais elevada na fase estacionária a 4 µmol fotões m-2 s-1. Existiram diferenças na expressão de mcyA entre as duas espécies. Em M. aeruginosa, a expressão foi máxima a 4 µmol fotões m-2 s-1 na fase de adaptação, já em P. agardhii foi máxima a 4 µmol fotões m-2 s-1 na fase exponencial de crescimento.

Os parasitas fúngicos zoospóricos são ubíquos nos sistemas aquáticos e a infeção de fitoplâncton por estes fungos é um fenómeno comum em águas doces. Os fungos parasitas de fitoplâncton pertencem principalmente ao filo Chytridiomycota (quitrídeos) e distinguem-se de outros fungos por produzirem zoósporos flagelados. Estes fungos parasitas podem infetar vários tipos de fitoplâncton incluindo espécies de cianobactérias formadoras de florescências. No entanto, existe pouca informação sobre o efeito destas infeções na ocorrência, periodicidade e toxicidade das florescências cianobacterianas. O estudo aprofundado destas interações é dificultado, pelo facto destes fungos serem dificeis de visualizar ao microcópio, pela falta de métodos de detecção alternativos à microscopia e, sobretudo, pela dificuldade de cultivar estes organismos e de obter culturas puras. Neste estudo reportamos a ocorrência de parasitismo quítrideo numa florescência de P. agardhii em águas superficiais portuguesas e descrevemos o isolamento e manutenção em cultura monoclonal deste parasita de P. agardhii. A obtenção de culturas puras possibilitou o acesso a DNA para testar a aplicablidade de um método já descrito para fungos zoospóricos na detecção e quantificação deste parasita de P. agardhii em amostras naturais. As culturas obtidas e o sucesso na aplicação do método de PCR em tempo-real para quantificação deste parasita de P. agardhii possibilitam o estudo deste parasitismo cuja influência na dinâmica de florescência é ainda pouco conhecida.

A cianobactéria Planktothrix agardhii forma blooms persistentes em reservatórios de água doce superficiais e está frequentemente associada à presença de microcistinas. No entanto, densidades celulares elevadas de P.agardhii nem sempre correspondem a níveis elevados de microcistinas e vice-versa. As florescências de Planktothrix sp. são constituídas por estirpes tóxicas e não-tóxicas que são visualmente indistinguíveis. Contudo, as estirpes tóxicas podem ser quantificadas molecularmente uma vez que possuem um conjunto de genes envolvidos na síntese de microcistinas, onde se inclui o gene mcyA. Neste trabalho, foi monitorizada uma florescência perene de P.agardhii durante dois anos (2012-2014), com o objectivo de caracterizar a variabilidade temporal dos genótipos tóxicos e concentração de microcistinas. Foram também medidos vários parâmetros físico-químicos (nitratos, fósforo total, pH e condutividade) e biológicos (presença de quitrídeos parasitas nos tricomas de P.agardhii). A concentração total de microcistina na água foi medida por ELISA. O nº de cópias do gene mcyA e do gene 18SrDNA de fungos quitrídeos foi quantificado por PCR em tempo-real. Os resultados demonstraram que a quantidade do gene mcyA e a concentração de microcistina total variam ao longo do tempo estando ambos correlacionados (coeficiente de correlação de Spearman de 0,84). O período em que a concentração do gene mcyA e de microcistina foi mais elevado coincidiu com a presença de parasitas quitrídeos da cianbactéria P.agardhii. A quantidade do gene 18SrDNA correlaciona-se com o gene mcyA (coeficiente de correlação de Spearman de 0,83) e com a concentração de microcistina (coeficiente de correlação de Spearman de 0,82). Não houve qualquer correlação entre os parâmetros físico-químicos e a concentração do gene mcyA e de microcistinas. Face aos resultados obtidos colocam-se questões que interessa explorar: Qual será a influencia dos parasitas quitrídeos na modelação da densidade e toxicidade das florescências de P.agardhii? Será que a sua presença favorece o aparecimento de florescências tóxicas? Que factores influenciam a relação parasitas quitrídeos- Planktothrix?