Bacigalupe L.D.,Austral University of Chile |
Soto-Azat C.,Andrés Bello University |
Garcia-Vera C.,Direccion General de Aguas |
Barria-Oyarzo I.,Austral University of Chile |
Rezende E.L.,Andrés Bello University
Global Change Biology | Year: 2017
Chytridiomycosis, due to the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. Because conservation programs are implemented locally, it is essential to understand how the complex interactions among host species, climate and human activities contribute to Bd occurrence at regional scales. Using weighted phylogenetic regressions and model selection, we investigated geographic patterns of Bd occurrence along a latitudinal gradient of 1500 km within a biodiversity hot spot in Chile (1845 individuals sampled from 253 sites and representing 24 species), and its association with climatic, socio-demographic and economic variables. Analyses show that Bd prevalence decreases with latitude although it has increased by almost 10% between 2008 and 2013, possibly reflecting an ongoing spread of Bd following the introduction of Xenopus laevis. Occurrence of Bd was higher in regions with high gross domestic product (particularly near developed centers) and with a high variability in rainfall regimes, whereas models including other bioclimatic or geographic variables, including temperature, exhibited substantially lower fit and virtually no support based on Akaike weights. In addition, Bd prevalence exhibited a strong phylogenetic signal, with five species having high numbers of infected individuals and higher prevalence than the average of 13.3% across all species. Taken together, our results highlight that Bd in Chile might still be spreading south, facilitated by a subset of species that seem to play an important epidemiological role maintaining this pathogen in the communities, in combination with climatic and human factors affecting the availability and quality of amphibian breeding sites. This information may be employed to design conservation strategies and mitigate the impacts of Bd in the biodiversity hot spot of southern Chile, and similar studies may prove useful to disentangle the role of different factors contributing to the emergence and spread of this catastrophic disease. © 2017 John Wiley & Sons Ltd.
Dussaillant A.,University of Concepción |
Dussaillant A.,University of Southampton |
Benito G.,CSIC - Center for Environmental Sciences |
Buytaert W.,University of Bristol |
And 4 more authors.
Natural Hazards | Year: 2010
Five similar glacial-lake outburst floods (GLOFs) occurred in April, October, December 2008, March and September 2009 in the Northern Patagonia Icefield. On each occasion, Cachet 2 Lake, dammed by the Colonia Glacier, released circa 200-million m3 water into the Colonia River. Refilling has occurred rapidly, such that further outbreak floods can be expected. Pipeflow calculations of the subglacial tunnel drainage and 1D hydraulic models of the river flood give consistent results, with an estimated peak discharge surpassing 3,000 m3 s-1. These floods were larger in magnitude than any flood on record, according to gauged data since 1963. However, geomorphological analysis of the Colonia valley shows physical evidence of former catastrophic outburst floods from a larger glacial-lake, with flood discharges possibly as high as 16,000 m3 s-1. Due to potential impacts of climate change on glacier dynamics in the area, jökulhlaups may increase future flood risks for infrastructure and population. This is particularly relevant in view of the current development of hydropower projects in Chilean Patagonia. © 2009 Springer Science+Business Media B.V.
Segawa T.,Transdisciplinary Research Integration Center |
Segawa T.,Japan National Institute of Polar Research |
Takeuchi N.,Chiba University |
Yamada A.,Tokyo Institute of Technology |
And 6 more authors.
Environmental Microbiology Reports | Year: 2013
Antibiotic resistance genes are biologically transmitted from microorganism to microorganism in particular micro-environments where dense microbial communities are often exposed to an intensive use of antibiotics, such as intestinal microflora, and the soil microflora of agricultural fields. However, recent studies have detected antibiotic-resistant bacteria and/or antibiotic resistance genes in the natural environment geographically isolated from such areas. Here we sought to examine the prevalence of antibiotic resistance genes in 54 snow and ice samples collected from the Arctic, Antarctic, Central Asia, North and South America and Africa, to evaluate the level of these genes in environments supposedly not affected by anthropogenic factors. We observed a widespread distribution of antibiotic resistance genes in samples from various glaciers in Central Asia, North and South America, Greenland and Africa. In contrast, Antarctic glaciers were virtually free from these genes. Antibiotic resistance genes, of both clinical (i.e. aac(3), blaIMP) and agricultural (i.e. strA and tetW) origin, were detected. Our results show regional geographical distribution of antibiotic resistance genes, with the most plausible modes of transmission through airborne bacteria and migrating birds. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.
Oyarzun R.,University of La Serena |
Godoy R.,University of La Serena |
Nunez J.,Centro Del Agua Para Zonas Aridas Y Semiaridas Of America Latina Y El Caribe Cazalac |
Fairley J.P.,University of Idaho |
And 3 more authors.
Journal of Arid Environments | Year: 2014
The analysis of baseflow recession of streamflow has been widely used in the evaluation of basin scale parameters because the required data are inexpensive to acquire, and the method is easy to use and generally gives good results. A literature review, however, shows that few studies have examined the applicability of recession methods to arid basins, particularly those set in mountainous landscapes. In this study, we apply a recession method that uses a non-dimensional theoretical curve matching technique to evaluate basin-wide, spatially-averaged hydraulic parameters for several watersheds (Culebrón, Punitaqui, Valle Hermoso, Hurtado, Chalinga, and Camisas), taking as case of study the Coquimbo Region, an arid, mountainous territory with steep topography in North-Central Chile. The studied watersheds range from 200 to 1500km2. Results show hydraulic conductivity values in a reasonable range, i.e., 10-4 to 10-6ms-1, rather close to those reported in the few existing studies for some of the basins. The method also yields estimates on the order of 10-5 for drainable porosity, with no major differences between the basins. The recession flow analysis provides a cost-effective approach to obtaining bulk hydrological parameters in arid and semi-arid steep basins such as those of the Coquimbo Region and elsewhere. © 2014 Elsevier Ltd.
PubMed | Direccion General de Aguas, Austral University of Chile and Andrés Bello University
Type: | Journal: Global change biology | Year: 2017
Chytridiomycosis, due to the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. Because conservation programs are implemented locally, it is essential to understand how the complex interactions among host species, climate and human activities contribute to Bd occurrence at regional scales. Using weighted phylogenetic regressions and model selection, we investigated geographic patterns of Bd occurrence along a latitudinal gradient of 1,500 km within a biodiversity hotspot in Chile (1,845 individuals sampled from 253 sites and representing 24 species), and its association with climatic, socio-demographic and economic variables. Analyses show that Bd prevalence decreases with latitude though it has increased by almost 10% between 2008 and 2013, possibly reflecting an ongoing spread of Bd following the introduction of Xenopus laevis. Occurrence of Bd was higher in regions with high gross domestic product (particularly near developed centers) and with a high variability in rainfall regimes, whereas models including other bioclimatic or geographic variables, including temperature, exhibited substantially lower fit and virtually no support based on Akaike weights. In addition, Bd prevalence exhibited a strong phylogenetic signal, with five species having high numbers of infected individuals and higher prevalence than the average of 13.3% across all species. Taken together, our results highlight that Bd in Chile might still be spreading south, facilitated by a subset of species that seem to play an important epidemiological role maintaining this pathogen in the communities, in combination with climatic and human factors affecting the availability and quality of amphibian breeding sites. This information may be employed to design conservation strategies and mitigate the impacts of Bd in the biodiversity hotspot of southern Chile, and similar studies may prove useful to disentangle the role of different factors contributing to the emergence and spread of this catastrophic disease. This article is protected by copyright. All rights reserved.
Minora U.,Comitato EvK2CNR |
Minora U.,University of Milan |
Minora U.,Polytechnic of Milan |
Godone D.,Comitato EvK2CNR |
And 11 more authors.
Geografia Fisica e Dinamica Quaternaria | Year: 2015
Snowmelt contributes largely to water budget of several Chilean mountain watersheds. To describe snow covered area (SCA) variability within 18 watersheds in Central Chile during 2008-2011 we used MODIS data (i.e. MOD10A2-V5 maximum snow cover extent in eight-day periods). The study area was divided into three different zones (Northern, Central, and Southern), due to its large extent (205,000 km2), and according to former studies performed by the Direccíon General de Aguas (DGA) of the Chilean Government covering the time window 2000-2007. After georeferencing our data to the WGS84 Datum (UTM Projection, zone 19S), the scenes were cropped to fit the study area. We selected and set a threshold for cloud coverage (<30%) in order to discard the images with too cloud cover, so losing only 2% of the sample. Hypsographic and aspect analyses were performed using the SRTM3 elevation model. We found largest values of SCA during 2008-2011 in the Central Zone, while the topographic and climatic features (i.e. lower altitudes in the South, and a drier climate in the North) limit snow deposition elsewhere. Similarly, snow line is higher in the Northern zone (due to the presence of the plateau), and lower moving southwards. In the North the minimum SCA is reached sooner than elsewhere, lasting for a longer period (November to March). West side showed the maximum of SCA in all zones throughout the study period. The present work extends in time the dataset of SCA in the Central Chile, adding information for statistic assessment, and trend analysis of snow cover in this area.
Migliavacca F.,Polytechnic of Milan |
Confortola G.,Polytechnic of Milan |
Soncini A.,Polytechnic of Milan |
Senese A.,University of Milan |
And 4 more authors.
Geografia Fisica e Dinamica Quaternaria | Year: 2015
Glaciers of the central Andes have recently been retreating in response to global warming, with large consequences on the hydrological regime. We assessed here potential climate change impacts until 2100 upon the hydrologic regime of the largely snow-ice melt driven Maipo River basin (closed at El Manzano, ca. 4800 km2), watering 7 M people in the metropolitan region of Santiago de Chile. First, a weather-driven hydrological model including simplified glaciers' cover dynamics was set up and validated, to depict the hydrological regime of this area. In situ data from recent glaciological expeditions, ice thickness estimates, historical weather and hydrological data, and remote sensing data including precipitation from the Tropical Rainfall Measuring Mission (TRMM), and snow cover and temperature from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used for model set up. We subsequently forced the model with projections of temperatures and precipitations (plus downscaling) until 2100 from the GCM model ECHAM6, according to 3 different radiative concentration pathways (RCPs 2.6, 4.5, 8.5) adopted by the IPCC in its AR5. We investigated yearly and seasonal trends of precipitation, temperature and hydrological fluxes until 2100 under the different scenarios, in projection period (PR, 2014-2100), and we compared them against historically observed trends in control period (CP, 1980-2013). The results show potential significant increasing trends in temperature until 2100, consistently with observed historical trends, unless for Spring (OND). Precipitation varies more uncertainly, with no historically significant changes, and only few scenarios projecting significant variations. In the PR period, yearly flow decreases, significantly under RCP8.5 (-0.31 m3s-1). Flow decrease is expected especially in Summer (JFM) under RCP8.5 (-0.55 m3s-1). Fall (AMJ) flows would decrease slightly, while winter (JAS) flows are projected to increase, and significantly under RCP4.5 (+0.22 m3s-1), as due to sustained melting therein. Spring (OND) flows also would decrease largely under RCP8.5, down to -0.67 m3s-1, due to increased evapotranspiration for high temperatures.
Hydrological regime of remote catchments with extreme gradients under accelerated change: The Baker basin in Patagonia [Le régime hydrologique de bassins versants éloignés soumis á des gradients extrêmes et á de brusques changements: Le bassin de Baker en Patagonie]
Dussaillant J. A.,University of Greenwich |
Dussaillant J. A.,Center for Ecosystem Research in Patagonia |
Buytaert W.,Imperial College London |
Meier C.,University of Concepción |
And 2 more authors.
Hydrological Sciences Journal | Year: 2012
The Baker basin (27 000 km2) is located in one of the most pristine and remote areas of the planet. Its hydrological regime is poised to undergo dramatic changes in the near future due to hydropower development and climate change. The basin contains the second-largest lake in South America, and part of a major icefield. This study documents the natural baseline of the Baker River basin, discusses the main hydrological modes and analyses the potential for sustainable management. Annual precipitation varies several-fold from the eastern Patagonian steppes to the North Patagonian Icefield. The westernmost sub-basins are strongly governed by glacier melt with a peak discharge in the austral summer (January-March). The easternmost sub-basins have a much more seasonal response governed by quicker snowmelt in spring (November-December), while they exhibit low flows typical for semi-arid regions during summer and autumn. Topography, vegetation and wetlands may also influence streamflow. The strong spatio-temporal gradients and variability highlight the need for further monitoring, particularly in the headwaters, especially given the severe changes these basins are expected to undergo. The great diversity of hydrological controls and climate change pose significant challenges for hydrological prediction and management. © 2012 Copyright 2012 IAHS Press.
Balocchi F.,University of Arizona |
Balocchi F.,University of Talca |
Pizarro R.,University of Talca |
Morales C.,University of Talca |
Olivares C.,Direccion General de Aguas
Tecnologia y Ciencias del Agua | Year: 2014
This study analyzed four mathematical models for recessive flow estimation in order to determine which one would provide the best results for an Andean basin in Maule, central Chile. This was accomplished through the analysis of 25 summer floods occurring between 1971 and 2003, which identified groundwater as the exclusive supply as of the third inflection point of the falling limb of the storm's hydrograph. The results indicate that the exponential model 3 provides the best estimates. According to the Bland and Altman agreement test, the best model adjustment period was 240 hours.
Methodology to estimate lake turbidity using object-oriented classification of multispectral images [Metodología para estimación de la turbidez de un lago mediante la clasificación orientada a objetos de imágenes multiespectrales]
Quintana-Sotomayor C.,Direccion General de Aguas |
Lillo-Saavedra M.,University of Concepción |
Gonzalo-Martin C.,Technical University of Madrid |
Barrera-Berrocal J.A.,University of Concepción
Tecnologia y Ciencias del Agua | Year: 2012
This work implements an object-oriented multispectral image classification to quantify turbidity levels in the Grande Lagoon of San Pedro (Chile) (36° 51' S, 73° 06' W). The first step in this methodology is multiscale segmentation; then, to characterize the lagoon cover, different classes are defined according to the selection of training areas associated with data recorded in situ and texture descriptors. In the last stage, the accuracy of each test is evaluated using the Global Membership (PG) and the Global Stability (EG) indices proposed by this work and the results underwent a refinement process. The proposed methodology resulted in the creation of turbidity maps of the Grande Lagoon of San Pedro, Chile, where 86% of the lagoon surface is associated with a turbidity level between 1.0 and 1.7 NTU, indicating that the turbidity of this lagoon is low and homogeneous as compared to other lentic systems studied.