North Patagonian Research Articles

Triassic magmatism and metamorphism in the Antarctic Peninsula: Identifying the extent and timing of the Peninsula Orogeny

The mid to Late Triassic marks an episode of magmatism, deformation and metamorphism along the proto-Pacific margin of the Antarctic Peninsula and Patagonia. Calc-alkaline magmatism at ~227 Ma developed in a convergent margin setting across the central Antarctic Peninsula and North Patagonian Massif. Two distinct deformation and metamorphic events have been identified at ~221 Ma and ~207 Ma based on new U–Pb zircon ages from a metamorphic orthogneiss complex, investigated for the first time, from the elevated plateau region of central Palmer Land. These two events are interpreted to date the timing of the multi-phase Peninsula Orogeny, which correlates with the Chonide Event of central Patagonia. The onset of deformation in the Antarctic Peninsula is linked to tectonic events in central Patagonia and is associated with non-collisional slab dynamic processes during flat slab subduction in the Late Triassic. No consistent tectonic regime is evident during the mid-to Late Triassic episodes of deformation and metamorphism, but an initial period of extension/transtension (mid-Triassic) and a compressional regime in the Late Triassic is favoured in the Antarctic Peninsula and Patagonia. The newly acquired metamorphic ages provide no clear evidence for a segmented terrane model for the Antarctic Peninsula, as Late Triassic metamorphic ages are identified from across the central and eastern domains. New U–Pb zircon ages are also presented from a suite of strongly foliated granitoids that cross-cut the Triassic orthogneisses. They are dated in the interval 140–136 Ma and represent an episode of Early Cretaceous magmatism, transtensional deformation and widespread metamorphism across northwest and central Palmer Land.

The dynamics of primary growth in woody species from rain and transitional forests of Argentinean north Patagonia

The dynamics of primary growth in woody species from rain and transitional forests of Argentinean north Patagonia

Landscape factors modulating patterns of salmonid distribution during summer in north Patagonian rivers.

Understanding how ecosystem processes influencing fish distribution operate across spatial scales is important to understand biological invasions. Salmonids, originally from the Northern Hemisphere, have been repeatedly introduced throughout the world, making them an ideal group to test hypotheses about factors driving invasions. We assessed the influence of environmental variables at the watershed scale on the abundance and structure of salmonid assemblages in the breeding streams of the Upper Limay river basin, Rio Negro, Argentina. We combined field captures with digital map data and geographic information systems to examine landscape-level patterns of salmonid abundance in 35 representative sub-basins of the environmental gradient. We employed a hierarchical cluster analysis and classification and regression tree models to relate the abundance of salmonids and types of species assemblages with environmental characteristics at watershed level. We found stream localization, precipitation regime, altitude and air temperature to be important predictors of the abundance and assemblage structure of salmonids. Total catches showed an increasing gradient of catch-per-unit-effort from west to east and from north to south, with Oncorhynchus mykiss being the most abundant species. O. mykiss relative abundance was westward skewed, where smaller catchments with steeper and shaded valleys are drained by less productive streams with more irregular hydrological regimes, like those found in this species' North American native range. In contrast, the abundance of Salmo trutta abundance was eastward skewed, where larger, sunnier and more gently sloped catchments result in more productive streams with stable hydrological regimes, like those found in that species' European native range. Thus, differential salmonid abundance could result from the interplay between the evolutionary fingerprint left by each species' native environment (especially flow and temperature regimes) and the availability of those conditions in new environments to which they have been translocated. By furthering our understanding of how landscape conditioned invasion success, these findings can help guide the management of economically important introduced fish.

Implications for paleomobility studies of the effects of quaternary volcanism on bioavailable strontium: A test case in North Patagonia (Argentina)

Strontium isotopes (87Sr/86Sr) are used as geochemical tracers for paleomobility studies because they display predictable and stable patterns in ecosystems primarily controlled by the underlying geological regimes. While bedrock geology is stable over thousands of years, geomorphological processes can influence the 87Sr/86Sr in ecosystems over archeologically relevant timescales. Among these geomorphological processes, the deposition and reworking of volcanic sediments over Quaternary timescales are little studied but could be an important control of 87Sr/86Sr variations in many archeological regions. North Patagonia is a key archeological region to address animal and human movements, and an ideal location to test the influence of Quaternary volcanism on 87Sr/86Sr variation as it is located downwind of major volcanic centers. In this study, we aim to assess the main environmental and geological controls of bioavailable 87Sr/86Sr and to build a high-resolution isoscape using a machine learning regression framework for forthcoming paleomobility studies. We sampled several locations and analyzed different types of samples (N = 94). The ratios show a limited range of variation, which is not related to the bedrock geology. Rather, bioavailable 87Sr/86Sr variations display a progressive increase going eastward (away from the Andes), following dust aerosol deposition and elevation variations (R2 = 0.71, RMSE = 0.00041). We argue that this trend relates to the deposition and reworking of unradiogenic volcanic sediments by aeolian, fluvial and glacial erosion during the Quaternary. As most of this sediment reworking occurred during glacial periods, the current bioavailable 87Sr/86Sr variations across the study area likely represent a long-term average that varied little during the Holocene. Consequently, our isoscape provides a solid base for Holocene paleomobility studies in North Patagonia and underlines the importance of Quaternary volcanism processes for interpreting 87Sr/86Sr data in paleomobility studies in volcanic regions.

First report on seasonal abundance of malacostracans in the Allipén River (38°51′S, North Patagonia, Araucania Region, Chile)

First report on seasonal abundance of malacostracans in the Allipén River (38°51′S, North Patagonia, Araucania Region, Chile)

Implementing the monitoring breakdown structure: native lichens as biomonitors of element deposition in the southern Patagonian forest connected with the Puyehue volcano event in 2011-a 6-year survey (2006-2012).

This study aims to investigate the airborne elements' deposition by using native Usnea barbata lichens as biomonitors in the forested areas of Tierra del Fuego (TdF, southern Patagonia), an apparently pristine environment. The present study is linked to the volcanic eruption of the Puyehue-Cordón Caulle which started in north Patagonia in June 2011, which gives rise to long-distance transport of pollutants through the atmosphere at 1700km from our sampling sites. The monitoring breakdown structure (MBS) was applied to three sampling campaigns in 2006 (baseline)➔2011-2012 (3 and 15months after the volcanic event, respectively). We have on purpose enhanced the information variety endowment: (i) Seventy-one referenced sites were double sampled; (ii) up to 426 composite lichen samples were collected; (iii) twenty-six elements were measured by neutron activation analysis (As, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Rb, Sb, Sc, Se, Sm, Ta, Tb, Th, U, Yb, Zn) for samples of 2011 and 2012 campaigns; (iv) thirteen common elements (As, Ba, Ca, Co, Cr, Cs, Fe, K, Na, Sb, Se, U, Zn) were determined in 2006 for the baseline comparison. The natural contamination by tephras is reflected by lichens more clearly in the 2011 campaign, where Ba, Cr, Na, Ca, Cs, and U showed higher median levels compared with the baseline campaign (2006). Ca, K, and Na were the most accumulated elements after the volcano event and could be associated with the volcanic ashes' deposition. Rare earth elements (REEs) showed no significant bioaccumulation levels between 2011 and 2012, indicating their association with higher lithogenic inputs than volcanic ashes. Using the Earth's crust as reference, nine elements (As, Ba, Br, Ca, K, Na, Sb, Se, and Zn) presented moderate/significant mean enrichment factor (EF) values (> 5). The usefulness of Usnea barbata as test species for direct biomonitoring oriented kinetic studies in areas characterized by a low human impact is confirmed. Eventually, our results confirm that TdF is not an actual pristine environment as earlier supposed.

Quaternary tectonics in the southern Central Andes (37°-38° S): Retroarc compression inferred from morphotectonics and numerical models

A neotectonic study at the transitional segment between the Central and North Patagonian Andes, in the northern part of the Neuquén province in Argentina (37°-38°S) was carried out revisiting sites previously surveyed and addressing new field evidence from a morphotectonic perspective. Particularly, fieldwork in the Guañacos fold and thrust belt (GFTB) highlighted that the inner retroarc region at these latitudes has been dominated, almost exclusively, by a Quaternary compressive regime, contrarily to previous proposals that favored a strike-slip regime. The main structures affect upper Pliocene Cola de Zorro Formation and younger deposits, developing scarps up to 60 m in height. Numerical models were performed to simulate Guañacos fault activity and to test the reliability of the scarps and deformed strata as deformation markers. From these models, shortening rates of 0.04–0.06 mm/yr were calculated. In addition, new evidence of normal faulting in Pliocene rocks was revealed. In a more regional frame, we revised two models that introduced and explained the dextral faulting in this segment of the Andes during the Quaternary, which is well constrained by focal mechanisms at the arc zone. Even though seismological data reveal strike-slip deformation along the arc, our findings suggest that at the same latitudes in the inner retroarc zone, immediately to the east, strain partitioning is negligible and, although with low deformation rates, all this transitional region between the Central and North Patagonian Andes is affected by Quaternary compressional stresses controlling surface deformation. A major crustal boundary, i.e. the Arauco transition zone, might be exerting a first-order control in this particular stress-strain distribution.

Climate change impacts on agriculture's southern frontier – Perspectives for farming in North Patagonia

AbstractWinter chill is expected to decrease in many of the suitable growing regions for deciduous trees. Argentinean North Patagonia hosts extensive fruit tree cultivation, which provides an important contribution to both local and global food security. Using historic records from 11 weather stations from North Patagonia, we evaluate the possible impacts of climate change on fruit tree cultivation. We assess winter chill and seasonal heat availability, and the risk of spring frost events based on outputs from 15 Global Climate Models (GCMs) for two Representative Concentration Pathway (RCP) scenarios and two future time periods (represented by central years 2050 and 2085). Metrics were estimated for 47 years of records from the weather stations, as well as typical conditions for 10 past scenarios and 60 future GCM and RCP projections. Scenarios consisted of 100 plausible annual temperature records produced by a weather generator. Results suggest that fruit tree dormancy in Argentinean North Patagonia will not be strongly affected by climate change. Compared to the past, winter chill may only decrease by 9% in the RCP4.5 scenario by 2050 in the northeastern and eastern subregion, while in the central‐south and west the reduction seems unlikely to exceed 6% by the same RCP scenario and year. Our models project stable high growing season heat in the northeastern and eastern regions, and major increases in the south by 2085 in both RCP scenarios. Projections of spring frost events varied between 0 and about 25 hours below 0°C depending on the site. Increasing heat availability may create opportunities for fruit and nut growers to introduce new species and cultivars to the region. Our results provide a basis for planning such introductions and for enabling growers to exploit new opportunities for producing temperate orchard crops beyond their traditional ranges.

Sources and diffusive air–water exchange of polycyclic aromatic hydrocarbons in an oligotrophic North–Patagonian lake

Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds of environmental concern. This study aims to investigate the influence of local sources of anthropogenic PAHs and their air–water exchange fluxes in an oligotrophic North–Patagonian lake in Chile. The monitoring was carried out in Panguipulli Lake during a six-month period during the autumn and winter seasons (March to August 2017) using a high–volume air sampler and a pump system for water samples. We detected and quantified fifteen PAHs in the gas phase (mean ∑15PAHs = 11.6 ng m−3) and dissolved water phase (mean ∑15PAHs = 961.8 pg L−1). Methylphenanthrenes and pyrene dominated the concentrations of PAHs in the studied phases. To determine sources of PAHs we used the PAH ratios of Light Molecular Weight/Heavy Molecular Weight (∑LMW/∑HMW) and Phenanthrene/Anthracene (Phe/Ant). The PAH ratio results revealed a pyrogenic source. We estimated the air–water diffusive exchange fluxes and fugacity ratios for the studied compounds. In general, air–water diffusive exchanges of PAHs showed a net volatilization for the less hydrophobic (log KOW < 4) and lighter PAHs (MW ≤ 170 g mol−1), and a net deposition trend for the more hydrophobic (log KOW 4–7) and higher molecular weight PAHs (MW ≥ 178 g mol−1). We found a significant correlation between log water/air fugacity ratios and log KOW of PAHs. Therefore, it is suggested that this oligotrophic lake acts as a sink by accumulating hydrophobic and mid-high molecular weight PAHs derived mainly from pyrogenic sources. This study is the first attempt to understand the sources and behavior of PAHs in oligotrophic lakes in the Southern Chile where information is scarce regarding the occurrence of PAHs.

Integrating Multiple Techniques to Estimate Population Size of an Impacted Dusky Dolphin’s Population in Patagonia, Argentina

Successful conservation strategies require an accurate estimation of population size and this parameter is one of the most important factors that determine the rate of various evolutionary processes. In this study we integrated information from genetic, photo-identification and aerial surveys of dusky dolphins to determine the effective population size and the number of dolphins that inhabit the gulfs of Peninsula Valdes (GN and GSJ) and are exposed to tourism vessel traffic. Photo-identification sessions and biopsies samples were collected from a research vessel between 2004 and 2013 to estimate the number of dolphins in the area by capture-recapture methods and the effective population size using mtDNA data. In addition, 4 aerial surveys were carried out using line transects to estimate density via distance sampling. The long-term effective size estimated was 992.87-1103.19 individuals. During the photo-identification period and applying a mark rate of 0.416 the total estimated individuals in GN was 374 (95% CI:237-511). For GSJ the estimated individuals in the area was 55 (95% CI: 2-108, mark rate 0.692). From aerial surveys, the overall density estimate was D =0.13 dolphins/km2 (95% CI: 0.052 - 0.35; CV:49.60). The estimation for GN was 325 (95% CI:130-875), while for GSJ, was 104 (95% CI:42-280) individuals. These are the first estimations of the number and the effective population size for dusky dolphins in a small-scale area along north Patagonia. Dusky dolphins groups are impacted by anthropogenic activities, therefore the information reported here contributes population information to help to the species management and conservation.

Modelling the consequence of glacier retreat on mixotrophic nanoflagellate bacterivory: a Bayesian approach

Mixotrophic nanoflagellate bacterivory is affected by light; however, in glacially influenced lakes, glacial clay may also interfere with prey uptake. Mechanistic models based on prior quantitative hypotheses and tested with field data are useful for predicting these predator–prey interactions under a changing climate. We modelled the effect of glacial particles on the bacterivory of mixotrophic nanoflagellates, the dominant phytoplankton in mountain lakes in the North Patagonian Andes. Our model equation is based on the classical Michaelis–Menten formulation and Platt's photosynthesis–irradiance curve to account for the interference by glacial particles and the effect of light intensity, respectively. Bayesian inference was applied to estimate model parameters using data from field bacterivory experiments. Light experiments (LE) were performed in lakes with different levels of light penetration without clay particles, while clay experiments (CE) were performed with an experimental gradient of glacial clay concentration at constant light intensity. The LE showed a non‐monotonic effect of light intensity and the CE revealed an exponential negative effect of clay concentration. The obtained model was tested with two independent experiments carried out in a turbid proglacial lake. Our proposed mechanistic model successfully predicted the combined effect of light availability and particle interference on the mixotrophic nanoflagellate–bacteria relationship. The model demonstrated that the effect of light is dampened as clay concentration increases.

Timing and structure of vegetation, fire, and climate changes on the Pacific slope of northwestern Patagonia since the last glacial termination

By virtue of its location in the southern mid-latitudes, northwestern Patagonia (40°-44°S) offers the opportunity to unravel the mechanisms involved in the initiation and propagation of paleoclimate signals of hemispheric and global significance. Of particular importance is deciphering the evolution of the Southern Westerly Winds (SWW) considering their influence at continental, zonal, hemispheric, and global scale. Here I present a multi-decadal record from Lago Proschle, a small closed-basin lake located on the Pacific slope of northwestern Patagonia, to examine the timing and structure of vegetation, fire, and climate change along a continuum since the onset of the Last Glacial Termination (T1). The record shows rapid glacier recession during T1, reaching the western Andean foothills in ∼400 years or less. Nothofagus-dominated forests established between ∼17.4–17 ka, followed by closed-canopy North Patagonian Rain Forests (NPRF) with shade-tolerant thermophilous trees between ∼16.3–15.4 ka. These changes suggest an abrupt warming trend and an increase in precipitation at ∼16.3 ka, associated with a northward shift of the SWW. Subsequent increases in cold-tolerant hygrophilous trees between ∼15.4–12.8 ka imply a shift to cold, more humid conditions during the Antarctic Cold Reversal, suggesting stronger SWW influence. This was followed by stand-replacing fires brought by a sudden decline in summer precipitation at ∼12.8 ka, associated with a millennial-scale southward shift of the SWW which was contemporaneous with the onset of the Younger Dryas. Dominance of thermophilous, summer-drought tolerant Valdivian rainforest trees and high fire activity ensued between ∼10.3–7.8 ka, suggesting peak warmth and overall decline in annual precipitation associated with weakening of the SWW during the early Holocene. A multi-millennial cooling and wetting trend started at ∼7.8 ka, brought by stronger SWW influence, followed by recurrent, centennial-scale variations in temperature and precipitation starting at ∼6.4 ka. Deforestation, fire, and spread of non-native herbs by Chilean/European settlers began during the late 18th century. Abrupt vegetation changes in the Lago Proschle record were driven by rapid climate changes over the last 17,400 years amplified, in some instances, by fire disturbance.

Biometric Relationships between Otolith and Fish Size of the Main Demersal Resources of North Patagonia, Argentina

Allometric power equations are generated using otolith length and width in order to estimate the total length of five demersal species inhabiting the San Matias Gulf, the second largest gulf in Argentina. The selected fish species are economically important resources in Argentina and have been identified as prey for the system’s main predators. A total of 2795 specimens were sampled, and data were fitted using the nonlinear least squares analysis. It is shown that the length and width of the otolith are good predictors of the total fish length. A slightly better regression fit is observed when otolith length was considered as a predictor. Statistically significant morphometric differences in regression models were observed between sexes, except for Acanthistius patachonicus. Results are discussed and compared with those reported by other authors.

Late-Holocene vegetation dynamics and disturbance regimes in north Patagonia Argentina (40°S)

Natural disturbance processes such as volcanic eruptions, fire and human activities are important vegetation drivers in north Patagonia. Here, we tested the impact of volcanic ash fall and fire on vegetation composition analysing two sediment records, Lake Avutarda and Lake Bruja, located in the forest-steppe transition at 40°S. In addition, our analysis provides the first account on the history of Nothofagus alpina at its eastern distribution limits. Our results comprise the last 3000 years, indicating the persistence of the vegetation despite evident volcanic activity documented by numerous tephra layers in both records. Eleven fire episodes were identified, while redundancy analysis indicates a non-significant influence of fire activity on the vegetation. The population increase of Nothofagus alpina represents the most important change in vegetation composition in the last three millennia. We speculate that the presumed change in climate, which led to the expansion of Austrocedrus chilensis south of the study area, also caused the increase of Nothofagus alpina populations in the region.

Política de Estado en edición de libros en la norpatagonia: el Fondo Editorial Neuquino (FEN)

En el año 1989, la provincia de Neuquén crea el Fondo Editorial Neuquino (FEN) por Ley Nº 1.809 con el objetivo de publicar, difundir y vender obras de los escritores provinciales. Su puesta en funcionamiento y evolución fue dispar; a lo largo de los años tuvo diversas propuestas de modificación. La última de ellas, impulsada desde la Subsecretaría de Cultura (ahora con rango de Ministerio) concluyó a fines de 2018 en la redacción y aprobación de la Ley Nº 3.164, que la reemplaza.&#x0D; Este proyecto editorial se solapó en sus 30 años de existencia con otros aportes de entidades estatales para publicar libros neuquinos, y coincidió en sus inicios con otras legislaciones provinciales similares en la Norpatagonia: en Río Negro surgió el Fondo Editorial Rionegrino en 1984, y un año después en La Pampa se reglamentó el Fondo Editorial Pampeano.&#x0D; El presente trabajo describe y analiza el FEN poniendo de relieve particularidades de su redacción y puesta en funcionamiento. Busca discutir debilidades en su implementación, para contribuir al fortalecimiento de las estrategias públicas de edición de libros, considerando que la función del Estado para articular políticas activas es importante para promover e incrementar la bibliodiversidad del ecosistema libro argentino.

The Huncal Member of the Vaca Muerta Formation, Neuquén Basin of Argentina: Insight into biostratigraphy, structure, U-Pb detrital zircon ages and provenance

In the western sector of the Neuquén Basin, the organic-rich shales of the Vaca Muerta Formation are intercalated with turbidite sandstone intervals and slump structures integrated in the Huncal Member. The age of the Huncal sandstones based on the integration of the ammonite faunas, calcareous nannofossils and U-Pb analysis is late Berriasian in their type locality. The origin of this deposit is probably related with two lobes of turbiditic sandstones linked with a progradational regressive phase. Sandstones are lithic arkoses and feldspathic litharenites derived from recycled orogenic and dissected arc sources. The U-Pb ages confirm a mixed sedimentary provenance from the south and southeastern margins of the basin, specifically from Paleozoic and Triassic–Jurassic rocks of the North Patagonian Massif and the Huincul High. The complex fold and fault system described in the sandstone levels was interpreted as the result of slump processes with a main transport direction to the SW and W. Sandstone deposits with slump structures assignable to the Huncal Member are present throughout the entire basin from the Tithonian to the Valanginian in the Vaca Muerta Formation. Therefore, the Huncal Member is a diachronic lithostratigraphic unit and its deposition probably depended on different factors such as relative sea level changes, the position in the ramp system or in the platform and slope configuration and internal morphostructural features of the Neuquén Basin.

North Patagonian estuaries appear to function as nursery habitats for marble crab (Metacarcinus edwardsii)

Compared to other coastal habitats, estuaries are widely recognized to provide an important habitat for early stage crustacean development, such as recruitment, growth and survival. Thus, estuaries contribute to the reproductive population via the ontogenetic migration of mature crustaceans to other habitats. This study describes the spatial–temporal dynamics of the different ontogenetic stages of the Chilean marble crab (Metacarcinus edwardsii), the most harvested crab throughout Chile, in a northern Patagonian estuary. Crab traps were deployed monthly throughout the estuary and over a bathymetric gradient to evaluate the relative abundance of juveniles, pre-adults and adults. Crabs presented a clear segregated distribution dependent on ontogenetic stage, likely due to the migration of juveniles from the middle estuary to the outer section, which is associated with sexually mature individuals. Furthermore, a second bathymetric reproductive migration is identified for adults, characterized by a migration of mature individuals to deeper waters during winter and return to shallower waters during spring for mating. Understanding habitat use in exploited species, such as this marble crab, is crucial to effectively develop conservation and management strategies.

Geochronology, sedimentology and paleosol analysis of a Miocene, syn-orogenic, volcaniclastic succession (La Pava Formation) in the north Patagonian foreland: Tectonic, volcanic and paleoclimatic implications

The initial infill of the Patagonian Broken Foreland is related to Miocene, syn-orogenic, volcaniclastic successions accommodated in intermontane basins. In the last years several works have paid attention to these successions due to their role in the comprehension of the timing of deformation, the relationship between arc-volcanism and the environmental signals, and the climate changes related to the growth of the orogen. In this paper we perform the U-Pb geochronology and the sedimentologic and paleosols analyses of a Miocene, syn-orogenic, volcaniclastic succession (La Pava Formation) located at the northern part of Patagonian Broken Foreland. The results indicate that the syn-kinematic sedimentation (evidenced by growth strata and progressive unconformities) proceeded between ~19 Ma to ~14 Ma, associated with arc-derived volcaniclastic deposits, under alluvial conditions with profuse paleosols development. The facies analysis combined with the paleosols and provenance studies indicate episodic and cyclic supply of pyroclastic materials, which were mainly delivered from the catchment area of the system, affected by explosive volcanism. A succession of stacked paleosols was recorded into 3 sections, bounded by unconformities, which record from Alfisols-like, Vertisol-like to Andisols-like paleosols. Paleosols variations were related to the effects of tectonic events, climate changes or to the increase of volcanic supply in comparison to soil-forming processes. The results obtained in this work are considered substantial to unravel the tectonic, volcanic and paleoclimatic framework of the North Patagonian Andes.

Semi-commercial testing of regional yeasts selected from North Patagonia Argentina for the biocontrol of pear postharvest decays

The efficacy of two regional yeasts, Pichia membranifaciens NPCC 1250 and Vishniacozyma victoriae NPCC 1263, for controlling pear postharvest decay was evaluated at large scale (semi-commercial conditions) in two different packing houses. The human safety of the two yeast strains was initially assayed by assessing growth at body temperature, pseudohyphal growth, phospholipases production, and growth in simulated gastric juice. Subsequently, yeasts biomass was produced in a bioreactor (22 L) containing 18 L of culture medium based on sugarcane molasses plus urea. The produced biomass, with/without CaCl2 (2% w/v) addition, was used in biocontrol experiments carried out at semi-commercial scale on Beurre d'Anjou and Packham’s Triumph pears. Vishniacozyma victoriae NPCC 1263 plus CaCl2 showed high performance on controlling decay caused by Penicillium expansum and Botrytis cinerea. On Beurre d'Anjou cv, P. expansum and B. cinerea incidence was reduced by 70% and 100%, respectively, after 90 days of commercial storage. On Packham’s Triumph the incidence of the two decay forms was 63% after 150 days. The two antagonistic yeasts were able to establish and colonize the surface of the fruits, with an estimated increase in the population density of approximately three orders of magnitude during the postharvest period. This work is the first to evaluate and demonstrate the efficacy of local biocontrol experiments with regional yeasts under semi-commercial conditions.

Otoliths as indicators for fish behaviour and procurement strategies of hunter-gatherers in North Patagonia

This study evaluates the potential use of archaeological otoliths of Genidens barbus (Cuvier and Valenciennes) as a tool to study fish behavior and hunter-gatherers procurement strategies on the North Patagonian coast. The studied samples come from the San Antonio archaeological locality dated at ca. 1000-800 14C yr BP (Late Holocene). To assess whether exposure to fire significantly affects the otolith Sr:Ca and Ba:Ca ratios, burned and unburned modern lapilli otoliths have been analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry and no statistically significant differences were found between the results of both treatments. Core-to-edge chemical time series were carried out on ancient otoliths (ca. 1000 14C yr BP) in order to study the fish life history. Three amphidromous patterns were found for ancient samples. The capture environments and seasons inferred by the otolith edge chemistry and marginal increase, respectively, suggest a location in high salinity water (estuary and sea) in summer. Finally, to estimate the size of archaeological fish, a linear regression between total length and otolith length was constructed using 70 modern catfish otoliths. The size variability (358–610 mm) might indicate the use of non-selective capture techniques, probably nets, by hunter-gatherer groups.