Isolation and characterization of Pb-solubilizing bacteria and their effects on Pb uptake by Brassica juncea: implications for microbe-assisted phytoremediation

Autores:

Yahaghi, Z., Shirvani, M., Nourbakhsh, F., de la Peña, T.C., Pueyo, J.J., Talebi, M.

Resumen:

The aim of this study was to isolate and characterize lead (Pb)-solubilizing bacteria from heavy metal-contaminated mine soils and to evaluate their inoculation effects on the growth and Pb absorption of Brassica juncea. The isolates were also evaluated for their plant growth-promoting characteristics as well as heavy metal and salt tolerance. A total of 171 Pb-tolerant isolates were identified, of which only 15 bacterial strains were able to produce clear haloes in solid medium containing PbO or PbCO3, indicating Pb solubilization. All of these 15 strains were also able to dissolve the Pb minerals in a liquid medium, which was accompanied by significant decreases in pH values of the medium. Based on 16S rRNA gene sequence analysis, the Pb-solubilizing strains belonged to genera Bacillus, Paenibacillus, Brevibacterium, and Staphylococcus. A majority of the Pb-solubilizing strains were able to produce indole acetic acid and siderophores to different extents. Two of the Pb-solubilizing isolates were able to solubilize inorganic phosphate as well. Some of the strains displayed tolerance to different heavy metals and to salt stress and were able to grow in a wide pH range. Inoculation with two selected Pb-solubilizing and plant growth-promoting strains, (i.e., Brevibacterium frigoritolerans YSP40 and Bacillus paralicheniformis YSP151) and their consortium enhanced the growth and Pb uptake of B. juncea plants grown in a metal-contaminated soil. The bacterial strains isolated in this study are promising candidates to develop novel microbe-assisted phytoremediation strategies for metal-contaminated soils.

Año: 2018

Palabras claves: Metal-solubilizing bacteria, PGPR, contaminated soils, lead, phytoremediation

Decoding the gene coexpression network underlying the ability of Gevuina avellana to live in diverse light conditions

Autores:

Ostria-Gallardo, E., Ranjan, A., Ichihashi, Y., Corcuera, L., & Sinha, N.

Resumen:

Gevuina avellana (Proteaceae) is a typical tree from the South American temperate rainforest. Although this species mostly regenerates in shaded understories, it exhibits an exceptional ecological breadth, being able to live under a wide range of light conditions. Here we studied the genetic basis that underlies physiological acclimation of the photosynthetic responses of G. avellana under contrasting light conditions.
We analyzed carbon assimilation and light energy used for photochemical processes in plants acclimated to contrasting light conditions. Also, we used a transcriptional profile of leaf primordia from G. avellana saplings growing under different light environments in their natural habitat, to identify the gene coexpression network underpinning photosynthetic performance and light‐related processes.
The photosynthetic parameters revealed optimal performance regardless of light conditions. Strikingly, the mechanism involved in dissipation of excess light energy showed no significant differences between high‐ and low‐light‐acclimated plants. The gene coexpression network defined a community structure consistent with the photochemical responses, including genes involved mainly in assembly and functioning of photosystems, photoprotection, and retrograde signaling.
This ecophysiological genomics approach improves our understanding of the intraspecific variability that allows G. avellana to have optimal photochemical and photoprotective mechanisms in the diverse light habitats it encounters in nature.

Año: 2018

Palabras claves: Gene coexpression network, Gevuina avellana, light acclimation, photosynthesis, temperate rainforest

Antarctic rhizobacteria improve salt tolerance and physiological performance of the Antarctic vascular plants

Autores:

Gallardo-Cerda, J., Levihuan, J., Lavín, P., Oses, R., Atala, C., & Torres-Díaz, C., Cuba-Díaz, M., Barrera, A., Molina-Montenegro, M.A.

Resumen:

The two native Antarctic vascular plants, Deschampsia antarctica and Colobanthus quitensis, are mostly restricted to coastal habitats where they are often exposed to sea spray with high levels of salinity. Most of the studies regarding the ability of C. quitensis and D. antarctica to cope with abiotic stress have been focused on their physiological adaptations to tolerate cold stress, but little is known about their tolerance to salinity. We investigated whether rhizospheric bacteria associated to D. antarctica and C. quitensis improve the ability of Antarctic plants to tolerate salt stress. Salt tolerance was assayed in rhizospheric bacteria, and also their effects on the ecophysiological performance (photochemical efficiency of PSII, growth, and survival) of both plants were assessed under salt stress. A total of eight bacterial rhizospheric strains capable of growing at 4 °C were isolated. The strains isolated from D. antarctica showed higher levels of salt tolerance than those strains isolated from C. quitensis. The ecophysiological performance of C. quitensis and D. antarctica was significantly increased when plants were inoculated with rhizospheric bacteria. Our results suggest that rhizospheric bacteria improve the ability of both plants to tolerate salinity stress with positive effects on the adaptation and survival of vascular plants to current conditions in Antarctic ecosystem.

Año: 2018

Palabras claves: Salt tolerance, Antarctica, Plant growth-promoting rhizobacteria, Colobanthus quitensis, Deschampsia antarctica

Assessing potential Argentine Ant recruitment to pipping eggs in the Red-tailed Tropicbird on Rapa Nui (Easter Island)

Autores:

Varela, A., Luna, N., & Luna-Jorquera, G.

Resumen:

The invasive Argentine Ant, Linepithema humile, is known to prey on land bird chicks, but there are few reports of the ants’ impacts on breeding seabirds. We conducted a manipulative study using hen eggs to estimate the potential Argentine Ant recruitment to pipping eggs in the Red-tailed Tropicbird, Phaethon rubricauda, at Rapa Nui (Easter Island), Chile. Hen eggs were experimentally opened to simulate pipping eggs and control eggs were left unopened. The eggs were monitored for 90 min. The time elapsed until the arrival of the first ant did not differ between experimental and control eggs. None of the control eggs were visited by more than two ants. In contrast, the inferred cumulative number of ants that arrived at experimental eggs varied from 1 to >450. Simulated pipping eggs attracted a high number of ants in a short period of time, and the probability of an egg being attacked by ants after 5 and 60 min of exposure was 75% and 99%, respectively. A long-term monitoring study is needed to determine the actual Argentine Ant recruitment rate on pipping eggs, and the potential effects on the post-fledging survival rate of this native seabird which is threatened by a number of introduced species.

Año: 2018

Palabras claves: Invasive ants, Linepithema humile, breeding seabirds, Phaethon rubricauda, oceanic islands, south-eastern Pacific Ocean

Capture, swallowing, and egestion of microplastics by a planktivorous juvenile fish

Autores:

Ory, N., Gallardo, C., Lenz, M., & Thiel, M.

Resumen:

Microplastics (<5 mm) have been found in many fish species, from most marine environments. However, the mechanisms underlying microplastic ingestion by fish are still unclear, although they are important to determine the pathway of microplastics along marine food webs. Here we conducted experiments in the laboratory to examine microplastic ingestion (capture and swallowing) and egestion by juveniles of the planktivorous palm ruff, Seriolella violacea (Centrolophidae). As expected, fish captured preferentially black microplastics, similar to food pellets, whereas microplastics of other colours (blue, translucent, and yellow) were mostly co-captured when floating close to food pellets. Microplastics captured without food were almost always spit out, and were only swallowed when they were mixed with food in the fish's mouth. Food probably produced a ‘gustatory trap’ that impeded the fish to discriminate and reject the microplastics. Most fish (93% of total) egested all the microplastics after 7 days, on average, and 49 days at most, substantially longer than food pellets (<2 days). No acute detrimental effects of microplastics on fish were observable, but potential sublethal effects of microplastics on the fish physiological and behavioural responses still need to be tested. This study highlights that visually-oriented planktivorous fish, many species of which are of commercial value and ecological importance within marine food webs, are susceptible to ingest microplastics resembling or floating close to their planktonic prey.

Año: 2018

Palabras claves: Microplastic ingestion, Planktivorous fish, Juvenile, Seriolella violacea, Laboratory experiments, Microplastic egestion

Factors affecting the operational interaction between the South American sea lions and the artisan gillnet fishery in Chile

Autores:

Sepúlveda, M., Martínez, T., Oliva, D., Couve, P., Pavez, G., & Navarro, C., Stehlik, M., Durán, L.R., Luna-Jorquera, G.

Resumen:

The South American sea lion (SASL, Otaria byronia) is one of the species of pinnipeds that display the strongest level of conflict with fishing activities throughout its distribution range. However, little is known about potential temporal and/or spatial variations in the magnitude and effects of SASL and fishing interactions over an entire year and at different sites simultaneously. This study examines the factors that affect the intensity of the operational interaction between SASL and the artisan gillnet fishery in central Chile. Between 2014 and 2016, a total of 145 hauls at three artisan fishing coves were analyzed. South American sea lion interactions were observed in 82 of the 145 (56.6%) hauls analyzed, most frequently at the coves of San Antonio and El Membrillo. From the examined factors, Predation per Unit Effort increased with the number of SASL, however it decreased both during the summer and with greater distance from the nearest SASL colony. Artisan deterrent systems used by fishermen were found to be inefficient in avoiding the interactions with sea lions. Although the intensity of the interaction has increased in recent years (compared with previous studies in the area), the observed Catch per Unit Effort did not differ significantly during fishing trips with or without interaction, indicating that SASL is not a determining factor in the variation of artisan fishery catches. These results demonstrate that the intensity of interactions is not produced at random but rather it is related to factors that obey biological and ecological aspects of the SASL. These factors should be considered for the development of effective actions to prevent, or at least to reduce the interaction between SASL and artisan fisheries.

Año: 2018

Palabras claves: Fisheries, Pinnipeds, Operational interaction, Chile, Gillnet

Decadal modulation of the relationship between intraseasonal tropical variability and ENSO

Autores:

Guschina, D., Dewitte, B.

Resumen:

The El Niño Southern Oscillation (ENSO) amplitude is modulated at decadal timescales, which, over the last decades, has been related to the low-frequency changes in the frequency of occurrence of the two types of El Niño events, that is the Eastern Pacific (EP) and Central Pacific (CP) El Niños. Meanwhile ENSO is tightly linked to the intraseasonal tropical variability (ITV) that is generally enhanced prior to El Niño development and can act as a trigger of the event. Here we revisit the ITV/ENSO relationship taking into account changes in ENSO properties over the last six decades. The focus is on two main components of ITV, the Madden–Julian Oscillation (MJO) and convectively coupled equatorial Rossby waves (ER). We show that the ITV/ENSO relationship exhibits a decadal modulation that is not related in a straight-forward manner to the change in occurrence of El Niño types and Pacific decadal modes. While enhanced MJO activity associated to EP El Niño development mostly took place over the period 1985–2000, the ER activity is enhanced prior to El Niño development over the whole period with a tendency to relate more to CP El Niño than to EP El Niño. In particular the relationship between ER activity and ENSO was particularly strong for the period 2000–2015, which results in a significant positive long-term trend of the predictive value of ER activity. The statistics of the MJO and ER activity is consistent with the hypothesis that they can be considered a state-dependent noise for ENSO linked to distinct lower frequency climate modes.

Año: 2018

Palabras claves: Intraseasonal tropical variability, El Niño, Decadal modulation

Roof-integrated dew water harvesting in Combarbalá, Chile

Autores:

Carvajal, D., Minonzio, J., Casanga, E., Muñoz, J., Aracena, A., Montecinos, S., & Beysens, D.

Resumen:

Dew harvesting can be a supplementary source of freshwater in semiarid and arid areas. Several experiments on small-scale dew condensers (usually of 1 m2) have been carried out in many places in the world; however, few experiments have been conducted on large-scale collectors integrated into buildings. This work aims to assess one year of dew water harvesting in Combarbalá (Chile) using a painted galvanised steel roof as collecting surface. The roof (36 m2) was coated with a high-infrared-emissivity paint containing aluminosilicate minerals (OPUR, France). Dew measurements were conducted daily from September 2014 to August 2015. The dew yield and its relationship with meteorological variables were analysed. The results show that despite the low nocturnal relative humidity throughout the year (average: 48%), dew collection occurred on 56.1% of the recorded days. The daily average collection rate was 1.9 L d−1, with a maximum of 15 L d−1. The maximum daily dew yield is correlated strongly with relative humidity and correlated weakly with air temperature and wind speed. Considering the same rooftop can collect dew and rain, it was estimated that over one year dew water could contribute to roughly 8.2% of the total water collected, considering both sources.

Año: 2018

Palabras claves: Atmospheric water, dew collection, radiative cooling, water resources

Decadal modulation of the relationship between intraseasonal tropical variability and ENSO

Autores:

Gushchina, D., & Dewitte, B.

Resumen:

The El Niño Southern Oscillation (ENSO) amplitude is modulated at decadal timescales, which, over the last decades, has been related to the low-frequency changes in the frequency of occurrence of the two types of El Niño events, that is the Eastern Pacific (EP) and Central Pacific (CP) El Niños. Meanwhile ENSO is tightly linked to the intraseasonal tropical variability (ITV) that is generally enhanced prior to El Niño development and can act as a trigger of the event. Here we revisit the ITV/ENSO relationship taking into account changes in ENSO properties over the last six decades. The focus is on two main components of ITV, the Madden–Julian Oscillation (MJO) and convectively coupled equatorial Rossby waves (ER). We show that the ITV/ENSO relationship exhibits a decadal modulation that is not related in a straight-forward manner to the change in occurrence of El Niño types and Pacific decadal modes. While enhanced MJO activity associated to EP El Niño development mostly took place over the period 1985–2000, the ER activity is enhanced prior to El Niño development over the whole period with a tendency to relate more to CP El Niño than to EP El Niño. In particular the relationship between ER activity and ENSO was particularly strong for the period 2000–2015, which results in a significant positive long-term trend of the predictive value of ER activity. The statistics of the MJO and ER activity is consistent with the hypothesis that they can be considered a state-dependent noise for ENSO linked to distinct lower frequency climate modes.

Año: 2018

Palabras claves: Intraseasonal tropical variability, El Niño, Decadal modulation

Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼  30° S) based on a high-resolution atmospheric regional model

Autores:

Bravo, L., Ramos, M., Astudillo, O., Dewitte, B., & Goubanova, K.

Resumen:

Two physical mechanisms can contribute to coastal upwelling in eastern boundary current systems: offshore Ekman transport due to the predominant alongshore wind stress and Ekman pumping due to the cyclonic wind stress curl, mainly caused by the abrupt decrease in wind stress (drop-off) in a cross-shore band of 100 km. This wind drop-off is thought to be an ubiquitous feature in coastal upwelling systems and to regulate the relative contribution of both mechanisms. It has been poorly studied along the central-northern Chile region because of the lack in wind measurements along the shoreline and of the relatively low resolution of the available atmospheric reanalysis. Here, the seasonal variability in Ekman transport, Ekman pumping and their relative contribution to total upwelling along the central-northern Chile region (∼  30° S) is evaluated from a high-resolution atmospheric model simulation. As a first step, the simulation is validated from satellite observations, which indicates a realistic representation of the spatial and temporal variability of the wind along the coast by the model. The model outputs are then used to document the fine-scale structures in the wind stress and wind curl in relation to the topographic features along the coast (headlands and embayments). Both wind stress and wind curl had a clear seasonal variability with annual and semiannual components. Alongshore wind stress maximum peak occurred in spring, second increase was in fall and minimum in winter. When a threshold of −3  ×  10−5 s−1 for the across-shore gradient of alongshore wind was considered to define the region from which the winds decrease toward the coast, the wind drop-off length scale varied between 8 and 45 km. The relative contribution of the coastal divergence and Ekman pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate coastline. Roughly, coastal divergence predominated in areas with low orography and headlands. Ekman pumping was higher in regions with high orography and the presence of embayments along the coast. In the study region, the vertical transport induced by coastal divergence and Ekman pumping represented 60 and 40 % of the total upwelling transport, respectively. The potential role of Ekman pumping on the spatial structure of sea surface temperature is also discussed.

Año: 2016

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