North-central Chile Research Articles

Streamflow elasticity, in a context of climate change, in arid Andean watersheds of north-central Chile

ABSTRACT Based on a future temperature increase of 0.5°C and precipitation decrease of 25%, the climate elasticity of streamflow to precipitation and temperature changes in 12 Andean watersheds of the Coquimbo Region, north-central Chile, was assessed. Also, the possible relationships between this elasticity and specific physiographic characteristics of the watersheds (area, average elevation, slope distribution, terrain roughness, slope orientation, vegetation cover) were studied. Climate elasticity of streamflow ranged between 0 and 2.8. Watersheds presenting higher elevations, with a fairly well-balanced distribution of slope exposure tend to exhibit lower elasticity, which could be explained by the contribution of snowfall to the hydrological regime, more significant in those watersheds. Results should be considered when downscaling climate model projections at the basin scale in mountain settings. Finally, uncertainties in the approach, given by factors such as streamflow seasonality, data availability and representativeness and watershed characteristics, and therefore the scope of the results, are discussed.

Characterizing the Water Storage Capacity and Hydrological Role of Mountain Peatlands in the Arid Andes of North-Central Chile

High-altitude peatlands in the Andes, i.e., bofedales, play an essential role in alpine ecosystems, regulating the local water balance and supporting biodiversity. This is particularly true in semiarid Chile, where bofedales develop near the altitudinal and hydrological limits of plant life. The subterranean geometry and stratigraphy of one peatland was characterized in north-central Chile using Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR) and core extraction. Two sounding locations, two transversal and one longitudinal profile allowed a 3D interpretation of the bofedal’s internal structure. A conceptual model of the current bofedal system is proposed. Geophysical results combined with porosity measurements were used to estimate the bofedal water storage capacity. Using hydrological data at the watershed scale, implications regarding the hydrological role of bofedales in the semiarid Andes were then briefly assessed. At the catchment scale, bofedal water storage capacity, evapotranspiration losses and annual streamflow are on the same order of magnitude. High-altitude peatlands are therefore storing a significant amount of water and their impact on basin hydrology should be investigated further.

Comparative phylogeography, morphological boundaries and climate envelopes of two sympatric widespread Bromeliaceae from the southern Andes

AbstractWe studied the epiphytic species Tillandsia capillaris and T. virescens that grow as neotenic forms with autogamous and cleistogamous flowers. They have expanded in Andean mountain environments, where they grow sympatrically across most of their ranges in arid regions of Peru, central-western Bolivia and north-central Argentina and Chile. We studied the relationships between the two species and populations within each of them, the morphological boundaries and the climatic characterization of distinct genetic entities. We analysed 125 and 102 individuals from 25 and 27 populations of T. virescens and T. capillaris, respectively, by means of haplotype networks, phylogenetic and genetic structure analyses, using the plastid gene ycf1 (c. 4500 bp) to define genetic groups. Morphological studies by discriminant analyses and correlation with climatic variables extracted from WorldClim were used to test differentiations among the genetic groups within each species. We confirm that T. capillaris is a distinct entity and that T. virescens consists of three groups that diverged by vicariance from widespread ancestors. The high genetic diversity found in both species is consistent with the complex geography of the Andes and the Pleistocene glaciation cycles that have driven ecological speciation in both species reflected in the timing of divergence of the clusters.

Depositional Contexts and New Age Controls for Terminal-Pleistocene Megafauna in North-central Chile (31°50′S)

ABSTRACT Sites in north-central Chile have yielded late-Pleistocene megafauna bone remains, occasionally associated with human-made artifacts. However, little is known about the depositional characteristics, the conditions that allow their preservation, and how to identify recurrences facilitating their discovery. This work presents contextual and stratigraphic data, coupled with radiocarbon dates on bone material from surface findings and excavations conducted in Los Vilos (Coquimbo, Chile), which show that this area was rich in Pleistocene terrestrial mammals and that alluvial sequences and dunes have allowed bone preservation and exposure. These results have implications for the search for new evidence and for the interpretation of their historical trajectories. Radiometric age distribution indicates mainly terminal-Pleistocene specimens with the potential of some taxa persisting into the Holocene. These results are used to discuss coexistence and interaction scenarios between extinct faunas and the early record of human beings in the region.

Nurturing and Balancing the World: A Relational Approach to Rock Art and Technology from North Central Chile (Southern Andes)

Technology has been a central theme in archaeological discussion. Different approaches have been developed in order to understand and better explain the processes that lead to the production of objects and things. The anthropology of technology has been one such effort, with its focus on technological style and the chaîne opératoire. In this paper we argue that, despite their many contributions, these approaches tend to isolate the process of production, as well as to see it as the imposition of culture over nature. Instead, we propose a relational approach to technology, one that considers the multiple participants in the social actions involved, stressing the affective qualities of the different entities participating in the process of making. We focus this discussion on the production process of rock art in North Central Chile by Diaguita communities (c. ad 1000–c. 1540), arguing that making petroglyphs was a central activity that aimed at the balancing of the world and its participants, creating a mediating space that facilitated connectedness between the multiple members of the Diaguita world, humans and other-than-humans.

Population genetic structure and demographic history of the scallop Argopecten purpuratus from Peru and Northern Chile: implications for management and conservation of natural beds

The scallop Argopecten purpuratus is a heavily exploited resource along the coasts of Peru and north-central Chile, especially after El Nino events, when the species undergoes high increases in abundance. Little is known about its genetic structure or demographic history, two important factors to ensure sustainable exploitation. We sequenced the cytochrome oxidase I and cytochrome b genes of 116 individuals from six localities (between 05°44′S 80°53′W and 23°31′S 70°33′W). We found high levels of genetic diversity in the analyzed populations. No geographical structuring was observed in the haplotype network, which consisted of a few central, widely distributed haplotypes, and many derived population-specific haplotypes separated by few mutations. This pattern suggests a recent population expansion and moderate to low current gene flow among populations. Mismatch analysis, neutrality tests, and a Bayesian skyline analysis confirmed the occurrence of a past event of population expansion approximately 5,000 years ago, which coincides with increasingly stronger and more frequent El Nino events.

Ex-situ evaluation of cactus pear (Opuntia ficus-indica): establishment on amended mine tailings

In Chile, mining operations produce a lot of solid waste that is piled up (tailings); there are currently about 870 deposits, of which 746 are abandoned. In the semiarid Mediterranean climate of north-central Chile, the fine particles of dried tailings are exposed to physical agents such as wind and short, heavy rains, which can disperse them to the environment, contaminating waterways and surrounding soils. Cactus pear [Opuntia ficus-indica (L.) Mill.] cultivation could be an option for the phyto-stabilization of post-operative tailings in arid and semiarid zones, as its biomass can be used for clean energy production (among other productive uses). The present study evaluated the establishment of cactus pear on tailings amended with goat manure and mine leaching gravel at different rates. The experiment was conducted for 20 weeks under controlled laboratory conditions. Physical and chemical characteristics of the substrates and chemical characteristics of soil solution were determined. Additionally, both aerial and root biomass production and metal (Cu, Zn and Fe) concentration in roots and shoots were measured. The results indicated that application of both goat manure and mine leaching gravel increased the rooting capability of cactus pear on mine tailings. Even though differences in aerial biomass production were found between controls and the treatments, it is not possible to state that the application of these amendments results in increased production over a short period. Goat manure and mine leaching gravel applications decreased the bioavailability of mineral elements, reducing their translocation to aerial structures; however, they were not very effective at decreasing absorption of Cu by roots. It was not possible to ignore the possible external contamination of root tissues by metals. Salinization problems were detected in treatments in which goat manure was added, which affected root growth.

Framboidal chalcopyrite and bornite constrain redox conditions during formation of their host rocks in the copper stratabound mineralization of Picachos, north-central Chile

The Picachos Project is a copper deposit that occurs in manto-type orebodies in north-central Chile and it exhibits common features of Chilean stratabound or manto-type copper deposits: (1) an increase of copper contents from the margins to the centre of the orebodies; (2) sodic and potassic hydrothermal alteration of host rocks with subsequent chloritization and sericite alteration; and (3) its occurrence in sequences of limestones that are intercalated with volcanic rocks. The most salient characteristic of the Picachos Project is the presence of pervasive framboidal pyrite in both the non-mineralized limestones and the host rocks of the copper mineralization. These framboidal pyrites are well preserved, probably due to their close relationship with organic matter, and have no evident textures of overgrowth, recrystallization or dissolution. Moreover, framboidal chalcopyrite and bornite are formed in the external and internal areas, respectively, of the orebodies, sharing common morphological characteristics with framboidal pyrite, and are formed by the replacement of the original pyrite framboids, without changing their shape and size distribution. Representative size distributions of framboidal pyrite, chalcopyrite and bornite are determined using high-resolution X-ray tomography (micro-CT). This study highlights the effectiveness of these analytical techniques to obtain the representative size distribution of framboids in mineralized rocks. The preservation of the original framboidal texture of pyrite makes it possible to infer anoxic to near-dysoxic conditions. The size distributions of framboidal chalcopyrite and bornite are hypothesized to be additional potential paleo-redox indicators, referring to the same formation dynamic as typical framboidal pyrites.

Shallow intraplate seismicity related to the Illapel 2015 Mw 8.4 earthquake: Implications from the seismic source

The September 16, 2015, Mw 8.4 Illapel, Chile earthquake is the first large event occurring in north-central Chile after the 1943 earthquake, filling a known seismic gap in the region. The earthquake took place in a complex tectonic region, nearby an area where transition from erosive to accretionary margin occurs due to the collision of Juan Fernandez Ridge (JFR) along the Chilean margin. We inverted the kinematic rupture process of the 2015 Mw 8.4 Illapel earthquake from the joint inversion of teleseismic body waves and near-field data. The relative weighting between datasets and the weighting of spatial/temporal constraints are objectively estimated by applying the Akaike's Bayesian Information Criterion. The coseismic slip model yields a total seismic moment of 4.92 × 1021 Nm occurred over ~120 s. The rupture shows both downdip and updip propagation with slip extending along the thrust interface from ~50 km depth to shallow near-trench depths (<15 km), with maximum slip of ~9 m located at shallow depths, where low average rupture speeds ~1.8–2 km/s are estimated. Outer-rise events, triggered within the oceanic Nazca plate after the mainshock, did not penetrate into the mantle and are related to preexisting faults due to both bending of Nazca plate and JFR uplift, which promotes a tensional stress regime in the surrounding area. This seismicity was triggered by static stress transfer from near-trench slip revealed by our source rupture modelling, suggesting outer-rise seismicity as a proxy for near-trench coseismic slip. Crustal seismicity within continental South American plate is observed prior to, and after, the mainshock, mainly related to extensional faulting within eroded and fractured wedge due to tectonic processes along erosive margins. We also show evidence of shallow seismicity after the mainshock associated with a long-lived crustal fault, which can represent a high seismic hazard for La Serena-Coquimbo conurbation.

Consumption of aquatic macrophytes by the Red-gartered Coot Fulica armillata (Aves: Rallidae) in a coastal wetland of north central Chile

The Red-gartered Coot Fulica armillata, is a common herbivorous water bird in coastal wetlands of the southern Neotropical region. Microhistological analyses of feces collected at the coastal wetland of Punta Teatinos (north central Chile; ~29oS), show that this coot feeds predominantly on Stuckenia pectinata, the most abundant submerged macrophyte at this area. The foraging behavior of F. armillata is discussed in regard with its ecological role as a primary consumer on coastal wetlands.

Ecological and social correlates of natal dispersal in female and male Thorn-tailed Rayadito (Aphrastura spinicauda) in a naturally isolated and fragmented habitat

AbstractSex-biased natal dispersal is predicted to be a consequence of differences in the costs and benefits of dispersal perceived by each sex. Although female-biased dispersal has been described for numerous birds in heterogeneous landscapes, studies documenting sex-related differences in the causes and consequences of natal dispersal in fragmented habitats are comparatively scarce. We used capture-mark-recapture data and genetic analyses in a population of Thorntailed Rayadito (Aphrastura spinicauda) from north-central Chile in order to investigate how the possible causes and consequences of dispersal are linked to sex-specific dispersal behavior in a naturally isolated and fragmented forest habitat. We analyzed 36 recaptured post-fledging birds to test whether female-biased dispersal reflected differential responses between sexes to potentially long-term acting selective pressures related to habitat fragmentation and high population densities. In this population, females disperse long distances (median distance: 780 m), whereas males are mostly philopatric (median distance: 85 m). Results suggest that female dispersal is possibly a response to the local density of breeding birds and mate availability, and comes without apparent reproductive costs. Inbreeding avoidance was not evident, but females may already be decreasing the probability of mating with relatives by moving away from their natal neighborhood where male kin usually remain. Our findings also indicate that male dispersal, while reduced in relation to females, can result from a tradeoff between the social benefits of settling near the natal territory and the associated costs of high breeding densities and kin competition. An increase of paternity loss was evident for males moving long distances. Follow-up studies should assess the differences in the costs and benefits of within- and between-fragment dispersal in this population.

Revision of the Chilean Genus Diastoleus Solier (Coleoptera: Tenebrionidae), with a Preliminary Phylogenetic Analysis of the Tribe Scotobiini

The genus Diastoleus Solier (Tenebrioninae: Scotobiini) is composed of four species restricted to north-central Chile. Representatives of this genus are adapted to inhabit xeric environments. In this paper the genus is revised using external features, new genitalic characters, and internal morphology. A new species, D. costalenissp. nov., is described from Paposo, Antofagasta, northwestern Chile. Habitat records, distribution map, habitus photographs, drawings of metendosternites and aedeagi are included. A cladistic analysis was conducted to test the monophyly of the genus within the tribe Scotobiini.

Groundwater Recharge Assessment in an Arid, Coastal, Middle Mountain Copper Mining District, Coquimbo Region, North-central Chile

Groundwater recharge processes operating in a portion of the western slope of the Chilean Coastal Cordillera (30°S) were assessed. The study takes advantage of the presence of the Cerro Brillador Mine (CBM), currently part of the Universidad de La Serena mining research center. Six factors—slope, solar exposure, drainage density, lineament density, geology and vegetation were characterized in a 12 km × 12 km area around the mine to identify the zones of greatest and least potential for groundwater recharge. The analysis indicates that approximately 66% of the total area presents favorable conditions for recharge. At a more local scale, the work focused on the CBM itself, an experimental facility where structural measurements in the interior and exterior of the mine, monitoring of the water level in the shaft, and sampling of mine water for chemical and isotopic composition were carried out. The chemical analysis highlighted the lack of acid drainage, despite the existence of pyrite (FeS2) and copper-sulfate mineralization in the mine. The isotopic analysis showed that the groundwater has a similar signature to local precipitation. From this information, a simple conceptual model for the hydrogeology is proposed, in which precipitation rapidly recharges the mine along faults and joints with a preferential N-S strike, but is impounded by the Urrutia fault, which facilitates the storage of groundwater in the underground workings by acting as a flow barrier. A simple analysis suggests a recharge rate on the order of 5% of the average annual precipitation for the CBM area.

Artificial light pollution at night (ALAN) disrupts the distribution and circadian rhythm of a sandy beach isopod

Coastal habitats, in particular sandy beaches, are becoming increasingly exposed to artificial light pollution at night (ALAN). Yet, only a few studies have this far assessed the effects of ALAN on the species inhabiting these ecosystems. In this study we assessed the effects of ALAN on Tylos spinulosus, a prominent wrack-consumer isopod living in sandy beaches of north-central Chile. This species burrows in the sand during daylight and emerges at night to migrate down-shore, so we argue it can be used as a model species for the study of ALAN effects on coastal nocturnal species. We assessed whether ALAN alters the distribution and locomotor activity of this isopod using a light system placed in upper shore sediments close to the edge of the dunes, mimicking light intensities measured near public lighting. The response of the isopods was compared to control transects located farther away and not exposed to artificial light. In parallel, we measured the isopods’ locomotor activity in the laboratory using actographs that recorded their movement within mesocosms simulating the beach surface. Measurements in the field indicated a clear reduction in isopod abundance near the source of the light and a restriction of their tidal distribution range, as compared to control transects. Meanwhile, the laboratory experiments showed that in mesocosms exposed to ALAN, isopods exhibited reduced activity and a circadian rhythm that was altered and even lost after a few days. Such changes with respect to control mesocosms with a natural day/night cycle suggest that the changes observed in the field were directly related to a disruption in the locomotor activity of the isopods. All together these results provide causal evidence of negative ALAN effects on this species, and call for further research on other nocturnal sandy beach species that might become increasingly affected by ALAN.

Spatio-temporal characterization of Trypanosoma cruzi infection and discrete typing units infecting hosts and vectors from non-domestic foci of Chile.

BackgroundTrypanosoma cruzi is a protozoan parasite that is transmitted by triatomine vectors to mammals. It is classified in six discrete typing units (DTUs). In Chile, domestic vectorial transmission has been interrupted; however, the parasite is maintained in non-domestic foci. The aim of this study was to describe T. cruzi infection and DTU composition in mammals and triatomines from several non-domestic populations of North-Central Chile and to evaluate their spatio-temporal variations.Methodology/Principal findingsA total of 710 small mammals and 1140 triatomines captured in six localities during two study periods (summer/winter) of the same year were analyzed by conventional PCR to detect kDNA of T. cruzi. Positive samples were DNA blotted and hybridized with specific probes for detection of DTUs TcI, TcII, TcV, and TcVI. Infection status was modeled, and cluster analysis was performed in each locality. We detected 30.1% of overall infection in small mammals and 34.1% in triatomines, with higher rates in synanthropic mammals and in M. spinolai. We identified infecting DTUs in 45 mammals and 110 triatomines, present more commonly as single infections; the most frequent DTU detected was TcI. Differences in infection rates among species, localities and study periods were detected in small mammals, and between triatomine species; temporally, infection presented opposite patterns between mammals and triatomines. Infection clustering was frequent in vectors, and one locality exhibited half of the 21 clusters found.Conclusions/SignificanceWe determined T. cruzi infection in natural host and vector populations simultaneously in a spatially widespread manner during two study periods. All captured species presented T. cruzi infection, showing spatial and temporal variations. Trypanosoma cruzi distribution can be clustered in space and time. These clusters may represent different spatial and temporal risks of transmission.

Five new scorpion species of genus Brachistosternus (Scorpiones: Bothriuridae) from the deserts of Chile and Peru, with comments about some poorly studied diagnostic characters of the genus.

Five new scorpion species of genus Brachistosternus of Chile and Peru are described. Brachistosternus gayi n. sp. is a high Andean species of north central Chile. Brachistosternus philippii n. sp. occurs near the coast of Antofagasta. Brachistosternus misti n. sp. occurs at intermediates altitudes of southern Peru. Brachistosternus contisuyu n. sp. occurs in Lomas formation in southern Peru. Brachistosternus anandrovestigia n. sp. occurs in coastal areas of southern Peru, and is the second known species of the genus without metasomal glands or androvestigia. Two diagnostic characters are discussed: the Internal Laminar Apophysis of the right hemispermatophore, and the sternum macrosetae.

Damage assessment of the 2015 Mw 8.3 Illapel earthquake in the North-Central Chile

Destructive megathrust earthquakes, such as the 2015 Mw 8.3 Illapel event, frequently affect Chile. In this study, we assess the damage of the 2015 Illapel Earthquake in the Coquimbo Region (North-Central Chile) using the MSK-64 macroseismic intensity scale, adapted to Chilean civil structures. We complement these observations with the analysis of strong motion records and geophysical data of 29 seismic stations, including average shear wave velocities in the upper 30 m, Vs30, and horizontal-to-vertical spectral ratios. The calculated MSK intensities indicate that the damage was lower than expected for such megathrust earthquake, which can be attributable to the high Vs30 and the low predominant vibration periods of the sites. Nevertheless, few sites have shown systematic high intensities during comparable earthquakes most likely due to local site effects. The intensities of the 2015 Illapel earthquake are lower than the reported for the 1997 Mw 7.1 Punitaqui intraplate intermediate-depth earthquake, despite the larger magnitude of the recent event.

Groundwater recharge assessment in a rural, arid, mid-mountain basin in North-Central Chile

ABSTRACTA basic component of any hydrogeological study is the magnitude and temporal variation of groundwater recharge. This can be difficult to assess accurately, particularly in arid and semi-arid rainfed mid-mountain zones, as is the situation in the rural, low population density zones of North-Central Chile. In this study, recharge in the Punitaqui Basin, North-Central Chile, was characterized, contrasting the results of two methods: a modified Thornthwaite-Mather (MTM) and discharge recession analysis (DRA). We found a recharge rate of between 1 and 4% of average annual precipitation. Average recharge estimated by the MTM method is consistently higher than that estimated by DRA. Also, DRA tends to smooth the recharge values, resulting in a lower inter-annual variation coefficient. Both methods identified a threshold value of total annual precipitation, above which recharge can be expected to occur, of the order of 180 mm year−1, consistent with values reported in similar areas.

The use of groundwater crustacean communities as indicators for aquifers quality in the semi-arid region of north-central Chile

Chile has large extensions of arid and semi-arid regions throughout the whole country, where the intensive demands and use of water resources, especially groundwater for irrigations and mining activities, increased dramatically over the last decades. The aquifer depletions due to water abstraction for irrigation and nutrient loads, exert major alterations of water quality, groundwater recharge and the natural renewal rate. All these factors diminish the aquifer value for the users and contribute to the degradation of groundwater as environment and habitat for fauna. This intensive use of groundwater resources in Chile brought to significant social and economic benefits, but their inadequate management resulted in negative environmental, legal and socioeconomic consequences. In this study, we aimed at providing a first assessment of environmental alterations of groundwater ecosystems from agricultural watersheds in northern Chile by specifically evaluating the effects of nitrogen and pesticide loads on groundwater communities and identifing the ecosystem service alterations due to agricultural activities. The study has been performed in a glacial aquifer from Coquimbo region; 250 km north of Santiago de Chile, the floodplain of which is dominated by agriculture (fruits tress, vineyards). Due to low regional precipitations (100-240 mm/year) the aquifer is primarily recharged by snowmelt from the Andean chain and surface runoff. The relative groundwater levels, groundwater temperature, chemical analysis of nitrogen and total phosphorus and pesticide concentrations were examined, along with the evaluation of crustacean biodiversity and spatial distribution pattern. Stygofauna taxonomic richness and the presence of stygobites have been related more to groundwater level stability than to chemical water parameters indicating that over-exploitation has a negative impact on habitat suitability for groundwater invertebrates. Groundwater biota assessment is essential in understanding the impact produced by agriculture activities on groundwater as a resource and as ecosystem, a nexus that becomes more and more widely recognized. The rationale and the preliminary results of this study are summarized in the Suppl. material 1.

Subduction thermal structure, metamorphism and seismicity beneath north-central Chile

Massive M>8 earthquakes have repeatedly struck the coastal Chilean subduction megathrust at intervals of nearly ten years, and such tsunamigenic earthquakes have caused recurrent damage. A widely accepted mature seismic gap along the strongly coupled plate interface in northern Chile was filled unexpectedly by the occurrence of the 2014 Mw 8.2 Iquique earthquake, which occurred 130 years after the previous quake. This event revealed that our understanding of the state of seismogenesis along the Chilean margin is still poor. This study aims at investigating the temperature and water content distributions within the Nazca slab along a large portion of the Chilean margin. We employ 3-D time-dependent thermomechanical numerical models that incorporate up-to-date slab geometry and phase diagrams of hydrous minerals in the subducting plate to study the north-central Chilean (19 °S–33 °S) coupled megathrust, including the region where the slab is subhorizontal (28 °S–32 °S). Our modeling results show that most shallow off- and onshore interplate earthquakes in north-central Chile in the last decade have been mainly controlled by the phase transformation from lawsonite blueschist to amphibolite at shallow depths. On the other hand, some of the deep subduction seismicity is in good agreement with eclogitization within the oceanic crust and formation of harzburgite in the ultramafic rock in the lower slab. The M > 6 interplate earthquakes are estimated to occur where our models predict slab temperatures less than 400–600 °C and slab dehydration less than 0.03–0.05 wt%/km. Slow slip events tend to occur in regions where interplate temperatures are 400–600 °C (0.03–0.05 wt%/km). The activity level of regional interplate earthquakes and slow slip events is interpreted to be affected by the fluid release from and the temperature distribution in the Nazca slab.