Cultivo y crecimiento de dos especies de diatomeas bentónicas aisladas del Salar del Huasco (Norte de Chile, 20° S) a diferentes condiciones de temperatura, luz y nutrientes

Benthic diatoms are cultured usually under laboratory conditions to be used as a food source for other organisms, ofaquaculture interest or for biotechnological applications. Laboratory experiments demonstrate the incidence of the physicaland chemical variables on abundance and growth rates of diatoms. While macronutrients are usually selected and dosed intocommon culture mediums to meet the general requirements of a wide range of diatoms, the availability and optimizationof micronutrients are more susceptible to each organism’s particular physiological conditions. The aim of this study was tocharacterize the growth of two species of benthic diatoms isolated from the Salar de Huasco in batch cultures at differentconditions of temperature (10, 15 and 20 °C), light intensity (40, 80 and 120 ?mol m-2 s-1) and concentrations of silica (1.06x 10-4 M Na2SiO3 x 9H2O and 2.12 x 10-4 M Na2SiO3 x 9H2O) and selenium (10-8 M H2SeO3) in f/2 medium, on a lightdarkcycle of 18:6 h. Both Nitzschia epithemioides Grunow in Cleve & Grunow (1880) as Nitzschia sp. showed highermaximum cell densities (692800 ± 107704 and 649600 ± 68942 cells ml-1, respectively) and exponential growth rates(1.80±0.56 and 0.97±0.32 div. d-1, respectively) at the highest temperature (20°C). The light intensity to which the cultureswere exposed had no effect on cell density and exponential growth rate in both taxa. Regarding to nutrients, an increasein silicates concentrations on the culture medium could promote the growth of N. epithemioides and Nitzschia sp. since atendency was observed to higher cell densities (1.08 x 106 ± 84,639 and 1.32 x 106 ± 109,038 cells ml-1, respectively) andexponential growth rates (1.98 ± 0.44 and 0.95 ± 0.18 div. d-1, respectively) with respect at the normal f/2 medium and f/2medium plus selenium. Simultaneous addition of silicate and selenium to the culture medium increased the maximum celldensity of the two strains under study, but this increase was significant (p = 0.05) only for N. epithemioides and amongthe normal f/2 medium (719200 ± 116895 cells ml-1) and the f/2 medium with double the amount of silicate and selenium(1498800 ± 209599 cells ml-1). However, the exponential growth rates were not significantly different when comparedto those of the control (without the addition of silicate and selenium). In conclusion both N. epithemioides and Nitzschiasp shown an increased cell density and exponential growth rate at 20 °C. The different light intensities not significantlyinfluenced the growth of both taxa. An increase in the concentration of silicates or simultaneous increase in silicatesand selenium in the culture medium can be considered as possible strategy to increase cell density of benthic diatom N.epithemioides in batch cultures.de alimento de otros organismos de interés acuícola o para aplicaciones biotecnológicas. Experimentos de laboratoriodemuestran la incidencia de las variables físicas y químicas sobre la abundancia y tasas de crecimiento de las diatomeas.Mientras los macronutrientes están generalmente seleccionados y dosificados en los medios de cultivo más comunespara satisfacer los requerimientos generales de un amplio rango de diatomeas, la disponibilidad y optimización demicronutrientes son más susceptibles a las condiciones fisiológicas particulares de cada organismo. El objetivo de esteestudio fue caracterizar el crecimiento de dos especies de diatomeas bentónicas aisladas del Salar de Huasco en cultivostipo batch, a diferentes condiciones de temperatura (10, 15 y 20 °C), intensidad de la luz (40, 80 y 120 ?mol m-2 s-1), y concentraciones de sílice (1.06 x 10-4 M Na2SiO3 x 9H2O y 2.12 x 10-4 M Na2SiO3 x 9H2O) y selenio (10-8 M H2SeO3)en medio f/2, a un ciclo 18:6 h luz-oscuridad. Tanto Nitzschia epithemioides Grunow in Cleve & Grunow (1880) comoNitzschia sp, exhibieron las mayores densidades celulares máximas (692800 ± 107704 y 649600 ± 68942 células mL-1,respectivamente) y tasas de crecimiento exponencial (1,80 ± 0,56 y 0,97 ± 0,32 div. d-1, respectivamente) a la temperaturamás elevada (20 °C). La intensidad de luz a la cual los cultivos fueron expuestos no afectó la densidad celular y tasa decrecimiento exponencial en ambos taxa. En cuanto a los nutrientes, un incremento en la concentración de silicatos en elmedio de cultivo, podría favorecer el crecimiento de N. epithemioides y Nitzschia sp. ya que se observó una tendenciaal aumento en la densidad celular (1,08 x 106 ± 84.639 y 1,32 x 106 ± 109.038 células mL-1, respectivamente) y tasa decrecimiento exponencial (1,98 ± 0,44 y 0,95 ± 0,18 div. d-1, respectivamente) con respecto a los medios f/2 normal y f/2más selenio. La adición simultanea de silicato y selenio al medio de cultivo aumentó las densidades celulares máximas delas dos cepas bajo estudio, pero este aumento fue significativo (p = 0,05) sólo para N. epithemioides y entre los medios decultivo f/2 normal (719200 ± 116895 células mL?1) y medio f/2 con el doble de silicato y selenio (1498800 ± 209599 célulasmL-1). Sin embargo, las tasas de crecimiento exponencial no tuvieron diferencias significativas con el control (sin adiciónde silicato y selenio). En conclusión tanto N. epithemioides y Nitzschia sp. muestran un aumento en la densidad celular yla tasa de crecimiento exponencial a 20 °C. Las diferentes intensidades de luz evaluadas no influyeron significativamenteen el crecimiento de ambos taxa. Un aumento en la concentración de silicatos o aumento simultáneo de silicatos y selenioen el medio de cultivo puede ser considerado como posible estrategia para incrementar la densidad celular de la diatomeabentónica N. epithemioides en cultivos discontinuos

Floraciones de fitoplancton y variación de la estructura comunitaria fitoplanctónica en tres lagos someros eutróficos de Chile Central

The phytoplankton community of three eutrophic shallow lakes located in the same geographical area was compared over a period of three years. Although these lakes are similar in many respects (e.g. location, origin, average depth, high concentration of nutrients, human influence) develop very different phytoplankton communities. Lo Galindo is dominated by Zygnematophyceae, Cyanophyceae and Chlorophyceae, while in Lo Méndez the groups Dinophyceae and Bacillariophyceae and in Las Tres Pascualas the Chlorophyceae, Cryptophyceae and Euglenophyceae. In Lo Mendez and Lo Galindo are frequent blooms of different groups of algae (cyanobacteria, green algae, diatoms and dinoflagellates), which generated wealth increases at different times of the year, even in winter they were presented. In Las Tres Pascualas blooms were rare. The occurrence and frequency of blooms of species representatives of the M, C,Y and Lo functional groups, and VII, VI, IV and V morphological groups, reflect the eutrophic lakes, being indicative of the degree of contamination of these systems that influence their present and future use.La comunidad fitoplanctónica de tres lagos someros eutróficos ubicados en la misma zona geográfica fue comparada durante un periodo de tres años. Aunque estos lagos son similares en muchos aspectos (p.ej. ubicación, origen, profundidad media, alta concentración de nutrientes, influencia humana) desarrollan comunidades de fitoplancton muy diferentes. En Lo Galindo dominan Zygnematophyceae, Cyanophyceae y Chlorophyceae, en Lo Méndez Dinophyceae y Bacillariophyceae y en Las Tres Pascualas Chlorophyceae, Cryptophyceae y Euglenophyceae. En Lo Méndez y Lo Galindo se presentaron frecuentes floraciones de diferentes grupos de microalgas (cianobacterias, algas verdes, diatomeas y dinoflagelados), las que generaron aumentos de abundancia en diferentes épocas del año, incluso en invierno. En Las Tres Pascualas, las floraciones fueron poco frecuentes. La ocurrencia y frecuencia de floraciones de especies representantes de los grupos funcionales M, C, Y y Lo y morfológicos VII, VI, IV y V reflejan las condiciones eutróficas de los lagos, siendo indicadoras del grado de contaminación de estos sistemas que influencia su uso actual y futuro

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries

We statistically reconstruct austral summer (winter) surface air temperature fields back to ad 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good agreement between the results of the three methods on interannual and decadal timescales. The field reconstructions allow us to describe differences and similarities in the temperature evolution of different sub-regions of SSA. The reconstructed SSA mean summer temperatures between 900 and 1350 are mostly above the 1901-1995 climatology. After 1350, we reconstruct a sharp transition to colder conditions, which last until approximately 1700. The summers in the eighteenth century are relatively warm with a subsequent cold relapse peaking around 1850. In the twentieth century, summer temperatures reach conditions similar to earlier warm periods. The winter temperatures in the eighteenth and nineteenth centuries were mostly below the twentieth century average. The uncertainties of our reconstructions are generally largest in the eastern lowlands of SSA, where the coverage with proxy data is poorest. Verifications with independent summer temperature proxies and instrumental measurements suggest that the interannual and multi-decadal variations of SSA temperatures are well captured by our reconstructions. This new dataset can be used for data/model comparison and data assimilation as well as for detection and attribution studies at sub-continental scales

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Cabbage and fermented vegetables : From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT(1)R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT(1)R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.Peer reviewe

Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity

Estructura comunitaria de diatomeas presentes en los sedimentos superficiales de ocho lagos andinos de Chile central

In this research the taxonomic structure of diatoms in sediments of high mountain lakes was studied. These lakes are located in Chile between 32°49' and 38°48' S in the Andean Cordillera. A total of 99 diatom taxa distributed in 48 genera were identified and all this taxa are cosmopolitan excepting a Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis and Pinnularia acidicola, which are know only for the Southern Hemisphere. The assemblages of diatoms were different in the studied lakes. So the high mountain lakes Ocho, Huifa, Ensueño and Negra, dominated benthic diatoms which are typical of oligotrophic and acid waters as Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola and Planothidium lanceolatum. In the assemblages from lakes Galletué, Icalma and Laja planktonic diatoms were more abundant, which are common in alkaline and mesotrophic waters, e.g., Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera and Rhopalodia gibba.En este trabajo se analizó la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontró un total de 99 taxa de diatomeas, distribuidos en 48 géneros. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepción de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que están descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composición florística de diatomeas. De esta manera, en los ensambles diatomológicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueño y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentónicas, típicas de aguas oligotróficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomológicos de los lagos Galletué, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctónicas, características de aguas alcalinas y mesotróficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibba

Estructura comunitaria de diatomeas presentes en los sedimentos superficiales de ocho lagos andinos de Chile central Diatoms community structure in superficial sediments of eight Andean lakes of central Chile

En este trabajo se analizó la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontró un total de 99 taxa de diatomeas, distribuidos en 48 géneros. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepción de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que están descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composición florística de diatomeas. De esta manera, en los ensambles diatomológicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueño y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentónicas, típicas de aguas oligotróficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomológicos de los lagos Galletué, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctónicas, características de aguas alcalinas y mesotróficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibba<br>In this research the taxonomic structure of diatoms in sediments of high mountain lakes was studied. These lakes are located in Chile between 32°49' and 38°48' S in the Andean Cordillera. A total of 99 diatom taxa distributed in 48 genera were identified and all this taxa are cosmopolitan excepting a Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis and Pinnularia acidicola, which are know only for the Southern Hemisphere. The assemblages of diatoms were different in the studied lakes. So the high mountain lakes Ocho, Huifa, Ensueño and Negra, dominated benthic diatoms which are typical of oligotrophic and acid waters as Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola and Planothidium lanceolatum. In the assemblages from lakes Galletué, Icalma and Laja planktonic diatoms were more abundant, which are common in alkaline and mesotrophic waters, e.g., Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera and Rhopalodia gibb