Cladóceros en el reservorio eutrofizado de Valle de Bravo. Estudio anual sobre su diversidad, distribución, abundancia y nuevos registros

Background. The Valle de Bravo reservoir is part of the Cutzamala system that supplies drinking water to Mexico City. For this reason, it is essential to guarantee its conservation and the quality of its waters. Due to the increased discharge of agrochemical pollutants and domestic wastewater discharges into the reservoir, the eutrophication of its waters has been accelerated. Eutrophication is associated with developing harmful cyanobacterial blooms (HCBs), which can affect aquatic communities. Goals. This study aimed to evaluate the diversity, species richness, and abundance of cladocerans in the Valle de Bravo reservoir and to determine the impact of this eutrophic environment. Methods. Zooplankton samples were obtained at six sampling stations through vertical throws, monthly during an annual cycle. Results. In total, 12 species of cladocerans were recorded, of which eight are new records for Valle de Bravo. The highest density of cladocerans occurred in March and June, with a notable decrease from August to November. Sampling sites S1, S2, and S4 had cladoceran densities higher than 60 ind. L-1. The species with the highest density was Bosmina longirostris, and five species were recorded throughout the year. The Shannon diversity index showed low values (1.0 a 1.48) associated with a eutrophic aquatic system. Conclusions. Even though the Valle de Bravo dam had blooms dominated by cyanobacteria at all times, the species richness was high compared to other freshwater ecosystems in Mexico, possibly reflecting that previous collection efforts were not intense enough to reflect the diversity and richness we recorded. Finally, the harmful effects of cyanobacterial blooms on aquatic biota cannot be ruled out.Antecedentes. El reservorio de Valle de Bravo forma parte del sistema Cutzamala que suministra agua potable a la Ciudad de México; por esta razón es fundamental el garantizar su conservación y la calidad de sus aguas. Debido al creciente incremento de contaminantes agroquímicos y la descarga de aguas residuales en el embalse, se ha acelerado la eutrofización de sus aguas, fenómeno que se asocia al desarrollo de florecimientos cianobacteriales nocivos (FCN,s), que pueden afectar a las comunidades acuáticas. Objetivos. El propósito de este estudio fue evaluar la diversidad, riqueza específica y abundancia de cladóceros en el reservorio de Valle de Bravo y determinar el impacto de este ambiente eutrófico sobre estas poblaciones. Métodos. Se realizaron colectas de zooplancton mediante arrastre vertical, en 6 estaciones de muestreo, mensualmente durante un ciclo anual. Resultados. En total se registraron 12 especies de cladóceros de las cuales ocho son nuevos registros para Valle de Bravo. La mayor densidad de cladóceros se presentó en los meses de marzo y junio, con una disminución notable de agosto a noviembre. Los sitios de muestreo S1, S2 y S4 tuvieron densidades de cladóceros mayores a 60 ind. L-1. La especie que tuvo la densidad más alta fue Bosmina longirostris y cinco especies se registraron durante todo el año. El índice de diversidad de Shannon mostró valores bajos (1.0 a 1.48), lo que se asocia con un sistema acuático eutrofizado. Conclusiones. A pesar de que el reservorio de Valle de Bravo tuvo en todo momento florecimientos dominados por cianobacterias, la riqueza de especies fue alta comparada con otros lugares en el país, lo que refleja posiblemente que los esfuerzos de colecta previos no fueron lo suficientemente intensos para reflejar la diversidad y riqueza que registramos. Finalmente, no se pueden descartar los efectos nocivos que los florecimientos cianobacteriales tienen sobre la biota acuática

Toxic effects of Pseudanabaena tenuis (Cyanobacteria) on the cladocerans Daphnia magna and Ceriodaphnia dubia

Some cyanobacteria can produce toxins that affect the aquatic biota and represent a human health risk. The cyanobacterium Pseudanabaena tenuis was isolated from the Valle de Bravo dam, and cultured in the laboratory under controlled conditions. We determined the acute toxic effects and performed a chronic (consumption) test in the cladocerans Daphnia magna (a reference test organism) and Ceriodaphnia dubia (a cosmopolitan species). To determine acute toxicity, three exposure ways were assayed: a) cell-free culture medium, b) crude cell extracts of the cyanobacterium after lysing, and c) aqueous extracts of P. tenuis phycobiliproteins. On the other hand, both cladocerans were fed P. tenuis, assessing the effects on survival and reproduction. For comparison, a control culture of both cladocerans was fed the green microalga Pseudokirchneriella subcapitata. Exposure to the cell-free culture medium did not produce any mortality in either cladoceran, but the aqueous and crude extracts generated acute toxicity. D. magna and C. dubia were negatively affected when fed P. tenuis, since their survival, total progeny, average number of neonates per clutch, and the number of clutches decreased. C. dubia was more sensitive than D. magna, both in the acute toxicity tests and to the effects of P. tenuis consumption. Although most of the blooms around the world are dominated by cyanobacteria of the genus Microcystis, attention should be given to other species, such as P. tenuis, because, frequently, it is not recognized that smaller cyanobacteria could exceed the larger species in terms of biomass, and produce noxious biological effect

Efecto de la temperatura y tipo de alimento en el cultivo de Moina micrura (Kurz, 1874) (Anomopoda: Moinidae) en condiciones de laboratorio

Moina micrura was grown at 20 and 25°C, fed with the green microalgae Ankistrodesmus falcatus andScenedesmus incrassatulus, at a food concentration of 300,000 cell ml-1. Survival, longevity and reproduction during a full life-cycle test were registered. Temperature was the only factor that produced significant effects in all the assessed responses. Food type produced significant differences in the average clutch size. Organisms grown at 25°C had the lowest survival and the largest total progeny per female. Time to first reproduction ranged from 3.6 to 6.6 days, with the lowest values at 25°C. The highest average longevity was observed for organisms fed with A. falcatus at 20°C (14.49 days). Average inter-clutch time ranged from 33.3 to 42.2 h, with the lowest value recorded at 25°C. The mean total progeny per female ranged from 41.1 to 57.9, for the organisms grown at 20 and 25°C respectively, and both fed with A. falcatus. The best results, regarding reproductive responses and longevity, were obtained for M. micrura fed with A. falcatus at 25°C. This cladoceran has a great potential for mass culture, and also may be used as a test organism in bioassays.Moina micrura fue cultivada a 20 y 25ºC, empleando como alimento las microalgas clorofíceas Ankistrodesmus falcatus y Scenedesmus incrassatulus, en concentración de 300,000 cél ml-1, evaluándose los efectos sobre la sobrevivencia y la reproducción a lo largo de su ciclo vital. De los parámetros evaluados, la temperatura fue el único factor que produjo diferencias estadísticamente significativas y únicamente el valor promedio de neonatos por camada fue afectado significativamente por el tipo de alimento (P<0.05). En general se observó que los organismos desarrollados a 25ºC tuvieron una sobrevivencia menor, aunque la progenie total por hembra fue mayor. El tiempo de la primera reproducción osciló entre 3.6 y 6.6 días, siendo menor a 25ºC. La longevidad promedio fue mayor en los organismos alimentados con A. falcatus a 20°C (14.90 días). El promedio del tiempo entre camadas fluctuó de 33.3 a 42.2 horas, registrándose el menor valor a 25°C. La progenie total promedio por hembra osciló en todos los tratamientos entre 57.9 (25°C) y 41.1 (20°C), para los organismos alimentados con A. falcatus. El mejor desarrollo de M. micrura se obtuvo en los cultivos a 25°C, empleando como alimento a Ankistrodesmus falcatus. De acuerdo a las respuestas reproductivas evaluadas, se confirma el uso potencial de esta especie para el cultivo masivo, así como para la obtención de organismos de prueba para bioensayos

Protective Effects of Human and Mouse Soluble Scavenger-Like CD6 Lymphocyte Receptor in a Lethal Model of Polymicrobial Sepsis

Sepsis still constitutes an unmet clinical need, which could benefit from novel adjunctive strategies to conventional antibiotic therapy. The soluble form of the scavenger-like human CD6 lymphocyte receptor (shCD6) binds to key pathogenic components from Gram-positive and -negative bacteria and shows time- and dose-dependent efficacy in mouse models of monobacterial sepsis. The objective of the present work was to demonstrate the effectiveness of infusing mouse and human sCD6 by different systemic routes, either alone or as adjunctive therapy to gold standard antibiotics, in a lethal model of polymicrobial sepsis. To this end, C57BL/6 mice undergoing high-grade septic shock induced by cecal ligation and puncture (CLP; ≥90% lethality) were infused via the intraperitoneal (i.p.) or intravenous (i.v.) route with shCD6 at different doses and time points, either alone or in combination with imipenem/cilastatin (I/C) at a dose of 33 mg/kg of body weight every 8 h. Significantly reduced mortality and proinflammatory cytokine levels were observed by i.p. infusion of a single shCD6 dose (1.25 mg/kg) 1 h pre- or post-CLP. When using the i.v. route, mice survival was significantly extended by starting shCD6 infusion at later time points post-CLP (up to 6 h after CLP). Significant adjunctive effects on mouse survival were observed by i.p. or i.v. infusion of shCD6 in combination with i.p. I/C post-CLP. Similar results were obtained in mice expressing high sustained levels (5 to 10 μg/ml) of mouse sCD6 in serum by means of transduction with hepatotropic adeno-associated virus (AAV). Taken together, the data support the conserved antibacterial effects of human and mouse sCD6 and their use as adjunctive therapy in experimental models of complex and severe polymicrobial sepsis.Ministerio de Economía y Competitividad (España) SAF2013-46151-R PCIN-2015-070Instituto de Salud Carlos III RD12/0015/0018European Development Regional Fund RD12/0015/0018Fundació La Marató TV3 201319-30-3

Using a new high-throughput video-tracking platform to assess behavioural changes in Daphnia magna exposed to neuro-active drugs

© 2019. ElsevierOne of the major challenges that faces today regulatory risk assessment is to speed up the way of assessing threshold sublethal detrimental effects of existing and new chemical products. Recently advances in imaging allows to monitor in real time the behaviour of individuals under a given stress. Light is a common stress for many different organisms. Fish larvae and many invertebrate species respond to light altering their behaviour. The water flea Daphnia magna as many other zooplanktonic species has a marked diel vertical phototactic swimming behaviour against light due to fish predation. The aim of this study was to develop a high throughput image analysis to study changes in the vertical swimming behaviour to light of D. magna first reproductive adult females exposed to 0.1 and 1 µg/L of four psychiatric drugs: diazepam, fluoxetine, propranolol and carbamazepine during their entire life. Experiments were conducted using a new custom designed vertical oriented four 50 mL chamber device controlled by the Noldus software (Netherlands). Changes in speed, preferred area (bottom vs upper areas) and animal aggregation were analysed using groups of animals under consecutive periods of dark and apical light stimulus of different intensities. Obtained results indicated that light intensity increased the speed but low light intensities allowed to better discriminate individual responses to the studied drugs. The four tested drugs decreased the response of exposed organisms to light: individuals move less, were closer to the bottom and at low light intensities were closer each other. At high light intensities, however, exposed individuals were less aggregated. Propranolol, carbamazepine and fluoxetine were the compounds effecting most the behaviour. Our results indicated that psychiatric drugs at environmental relevant concentrations alter the vertical phototactic behaviour of D. magna individuals and that it is possible to develop appropriate high-throughput image analysis devices to measure those responses.Peer ReviewedPostprint (author's final draft

Microcystins produced by filamentous cyanobacteria in urban lakes. A case study in Mexico City

Cyanobacterial blooms are of great importance because of the toxic effects that these microorganisms are able to induce, particularly on aquatic organisms. Microcystins (MCs) are the principal toxins biosynthesized by cyanobacteria and are powerful inhibitors of the protein phosphatases 1 and 2A. Zooplankton filter feeders such as cladocerans are directly affected by MCs as a result of ingestion of cyanobacteria or contact with intracellular products when cyanobacterial cells break up during and after blooms. A total of 17 strains of filamentous cyanobacteria isolated from three urban lakes in Mexico City were characterized using the microcystin synthetase region mcyA-Cd. Acute 48-h toxicity was evaluated in different strains using the cladoceran Daphnia magna and total microcystin content was determined by enzyme-linked immunosorbent assay (ELISA). The mcyA-Cd region was amplified in 16 microcystin-producing strains; microcystins were detected in eight strains with values ranging from 0.1422 to 2.772 µg L-1. Nevertheless, all aqueous crude extracts induced acute toxicity in D. magna with LC50 values from 363.91 to 741.8 mg L-1 (dry weight). The toxicity observed in non-microcystin-producing strains may be induced by cyclic peptides other than microcystins (anabaenopeptins, microviridins and cyclamides). The results obtained warn of the toxigenic potential of filamentous cyanobacteria, since though Microcystis spp. is frequently predominant in blooms, other toxins and intracellular metabolites released by filamentous cyanobacteria may induce toxicity on aquatic organisms as well as humans

Quinolone Resistance Reversion by Targeting the SOS Response

Suppression of the SOS response has been postulated as a therapeutic strategy for potentiating antimicrobial agents. We aimed to evaluate the impact of its suppression on reversing resistance using a model of isogenic strains of Escherichia coli representing multiple levels of quinolone resistance. E. coli mutants exhibiting a spectrum of SOS activity were constructed from isogenic strains carrying quinolone resistance mechanisms with susceptible and resistant phenotypes. Changes in susceptibility were evaluated by static (MICs) and dynamic (killing curves or flow cytometry) methodologies. A peritoneal sepsis murine model was used to evaluate in vivo impact. Suppression of the SOS response was capable of resensitizing mutant strains with genes encoding three or four different resistance mechanisms (up to 15-fold reductions in MICs). Killing curve assays showed a clear disadvantage for survival (Δlog10 CFU per milliliter [CFU/ml] of 8 log units after 24 h), and the in vivo efficacy of ciprofloxacin was significantly enhanced (Δlog10 CFU/g of 1.76 log units) in resistant strains with a suppressed SOS response. This effect was evident even after short periods (60 min) of exposure. Suppression of the SOS response reverses antimicrobial resistance across a range of E. coli phenotypes from reduced susceptibility to highly resistant, playing a significant role in increasing the in vivo efficacy

CARACTERIZACIÓN MORFOLÓGICA Y MOLECULAR DE CIANOBACTERIAS FILAMENTOSAS AISLADAS DE FLORECIMIENTOS DE TRES LAGOS URBANOS EUTRÓFICOS DE LA CIUDAD DE MÉXICO

Cyanobacteria are traditionally classifiedbased on morphological and ecologicaltraits, which can result in incorrect identifications due to phenotypic plasticity,and in the case of isolated strains, due tomorphological changes provoked by theculture conditions. The gene 16S rRNA isuseful for taxonomic identification, helpingto overcome the aforementioned problems.Using morphological and molecular characteristics, we isolated and identified filamentous cyanobacteria present in bloomsin three eutrophic urban lakes in MexicoCity with the aim of recognizing genera ofcyanobacteria other than Microcystis thatmay be present. Water samples were collected during March 2007, and through micromanipulation we obtained monospecificcultures that were preliminarily identifiedusing morphological traits. In addition,total DNA was extracted, and a partial region of the 16S rRNA gene was amplifiedto corroborate the taxonomic identifications; these were confirmed through theirphylogenetic positioning. In this way mostof the isolated strains identified by theirmorphological traits could be confirmed atthe generic level. We identified strains ofAnabaenopsis, Arthrospira, Leptolyngbya,Limnothrix, Geitlerinema, Phormidium,Planktolyngbya, Planktothrix, Pseudanabaena and Spirulina, showing the diversityof cyanobacteria that could be recordedin blooms even though the dominant taxacould be Microcystis spp. To accuratelydetermine taxonomic identity we stronglyrecommend the use of both techniques inorder to avoid errors due to phenotypicvariation provoked by environmental factors or culture conditions.Las cianobacterias se clasifican tradicionalmente con base en caracteres morfológicosy ecológicos, lo que puede resultar en unaasignación incorrecta debido a la plasticidad fenotípica de las cianobacterias, o enel caso de cepas aisladas debido a cambiosmorfológicos propiciados por las condiciones de cultivo. El uso del gen 16S rRNAes de gran utilidad para la identificacióntaxonómica, coadyuvando a superar losproblemas antes mencionados. En este estudio se aislaron e identificaron, mediantecaracteres morfológicos y moleculares, cianobacterias filamentosas presentes en florecimientos de tres lagos urbanos eutróficosde la ciudad de México, con el objetivo dereconocer otros géneros de cianobacteriasdiferentes a Microcystis, que pudieran estarpresentes en tales florecimientos. Durantemarzo de 2007 se colectaron muestras deagua y mediante micromanipulación se obtuvieron cultivos monocianobacteriales quefueron identificados preliminarmente conbase en caracteres morfológicos. Por otraparte, se extrajo el DNA total, se amplificó una región parcial del gen 16S rRNA y secorroboró la identificación taxonómica através de su posicionamiento filogenético.De esta manera se pudo identificar a lamayoría de los aislados mediante caracteresmorfológicos tradicionales, y confirmar suidentidad genérica con base en el análisisbioinformático del gen 16S rRNA. Así seidentificaron cepas de los géneros Anabaenopsis, Arthrospira, Leptolyngbya,Limnothrix, Geitlerinema, Phormidium,Planktolyngbya, Planktothrix, Pseudanabaena y Spirulina, resultado que muestrala diversidad que se puede registrar en florecimientos de cianobacterias, aun cuandoel taxón dominante pudiera ser Microcystisspp. A fin de poder determinar de maneramás precisa la identidad específica, serecomienda ampliamente el uso de ambastécnicas, ya que de esta forma se podríanevitar errores por variación fenotípica inducida por los estímulos ambientales o porlas condiciones de cultivo

Seasonal variation of <em>Microcystis aeruginosa</em> and factors related to blooms in a deep warm monomictic lake in Mexico

The occurrence of cyanobacterial blooms has increased globally over the last decades, with the combined effect of climate change and eutrophication as its main drivers. The seasonal dynamic of cyanobacterial blooms is a well-known phenomenon in lakes and reservoirs in temperate zones. Nevertheless, in the tropics, most studies have been performed in shallow and artificial lakes; therefore, the seasonal dynamic of cyanobacterial blooms in deep and eutrophic tropical lakes is still under research. We studied the seasonal variation of the phytoplankton community and the factors associated with Microcystis aeruginosa blooms along the water column of Lake Alberca de Tacámbaro, a warm monomictic crater lake located in Mexico, during 2018 and 2019. According to previous studies performed in 2006 and 2010, this lake was mesotrophic-eutrophic, with Chlorophyta and Bacillariophyta as the dominant groups of the phytoplankton community. During 2018 and 2019, the lake was eutrophic and occasionally, hypertrophic, a phenomenon likely associated with the increase of farmland area around the lake. The dominant species was M. aeruginosa, forming blooms from the surface to 10 m depth in winter, in the hypolimnion in spring and summer, and along the full water column in autumn. These findings suggest that M. aeruginosa in Lake Alberca de Tacámbaro displays seasonal and spatial population dynamics. Total phosphorus, dissolved inorganic nitrogen, water temperature and photosynthetically active radiation were the environmental factors related to M. aeruginosa blooms. Our results suggest that the changes in the structure of the phytoplankton community through time, and M. aeruginosa blooms in Lake Alberca de Tacámbaro, are mainly related to changes in land use from forest to farmland in areas adjacent to the lake, which promoted its eutrophication in the last years through runoffs. Comparative studies with other deep and eutrophic lakes will allow us to gain a deeper understanding of the dynamic of cyanobacterial blooms in natural and artificial water reservoirs strongly stressed by human activities

Aerosol optical characteristics from a summer campaign in an urban coastal Mediterranean area

The authors present a preliminary study of some optical properties of atmospheric aerosols over the area of Valencia, Spain, a coastal Mediterranean city. Measurements of spectral direct irradiance in the 300-1100 nm range were taken simultaneously at three sites: rural-continental, rural-coastal, and urban-coastal, all located within a 50 km radius of the city of Valencia. The irradiance measurements were obtained using three Li-cor 1800 spectroradiometers provided with radiance limiting tubes with field of views (FOVs) of 4.7/spl deg/. The measurements were made under clear sky conditions during a field campaign carried out in the summer of 1998. In order to avoid the uncertainties associated with the determination of the water vapor content and the other atmospheric constituents, the analysis of the spectral aerosol optical thickness (AOT) values was limited to the 400-670 mm spectral band. From the values of the spectral AOT, both the Angstrom coefficients and the aerosol size distributions were obtained. The results show the great dependence of the optical aerosol characteristic on the direction of the prevailing winds (maritime or continental) in this area