On the origin and processes controlling the elemental and isotopic composition of carbonates in hypersaline Andean lakes

H.J. and J.W.B. Rae acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement 805246).The Altiplano-Puna Plateau of the Central Andes hosts numerous lakes, playa-lakes, and salars with a great diversity and abundance of carbonates forming under extreme climatic, hydrologic, and environmental conditions. To unravel the underlying processes controlling the formation of carbonates and their geochemical signatures in hypersaline systems, we investigated coupled brine-carbonate samples in a high-altitude Andean lake using a wide suite of petrographic (SEM, XRD) and geochemical tools (δ2H, δ18O, δ13C, δ11B, major and minor ion composition, aqueous modelling). Our findings show that the inflow of hydrothermal springs in combination with strong CO2 degassing and evaporation plays an important role in creating a spatial diversity of hydro-chemical sub-environments allowing different types of microbialites (microbial mounds and mats), travertines, and fine-grained calcite minerals to form. Carbonate precipitation occurs in hot springs triggered by a shift in carbonate equilibrium by hydrothermal CO2 degassing and microbially-driven elevation of local pH at crystallisation. In lakes, carbonate precipitation is induced by evaporative supersaturation, with contributions from CO2 degassing and microbiological processes. Lake carbonates largely record the evaporitic enrichment (hence salinity) of the parent water which can be traced by Na, Li, B, and δ18O, although other factors (such as e.g., high precipitation rates, mixing with thermal waters, groundwater, or precipitation) also affect their signatures. This study is of significance to those dealing with the fractionation of oxygen, carbon, and boron isotopes and partitioning of elements in natural brine-carbonate environments. Furthermore, these findings contribute to the advancement in proxy development for these depositional environments.Peer reviewe

El uso de parámetros magnéticos en estudios paleolimnológicos en Antártida

En esta contribución se describen las distintas técnicas y mediciones magnéticas utilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útiles indicadores para realizar estudios relacionados con cambios climáticos y ambientales, así como herramientas de datación. Si bien es ampliamente conocida la utilidad de la susceptibilidad magnética, en primer lugar se discute el potencial y necesidad del uso de parámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes (natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos. A continuación se presentan resultados magnéticos obtenidos en sedimentos lacustres del Archipiélago James Ross (NE de la Península Antártica) como un caso de estudio. Se complementa con estudios sedimentológicos, hidroquímicos, geoquímicos y de estadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relación con los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analiza además el uso de las paleointensidades relativas como herramienta de datación en lagunas antárticas

El uso de parámetros magnéticos en estudios paleolimnológicos en Antártida

En esta contribución se describen las distintas técnicas y mediciones magnéticasutilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útilesindicadores para realizar estudios relacionados con cambios climáticos y ambientales,así como herramientas de datación. Si bien es ampliamente conocida la utilidad de lasusceptibilidad magnética, en primer lugar se discute el potencial y necesidad del uso deparámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes(natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos. Acontinuación se presentan resultados magnéticos obtenidos en sedimentos lacustresdel Archipiélago James Ross (NE de la Península Antártica) como un caso de estudio.Se complementa con estudios sedimentológicos, hidroquímicos, geoquímicos y deestadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relacióncon los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analizaademás el uso de las paleointensidades relativas como herramienta de datación enlagunas antárticas

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Spatial variability of the modern radiocarbon reservoir effect in the high-altitude lake Laguna del Peinado (southern Puna Plateau, Argentina)

The high-altitude lakes of the Altiplano–Puna Plateau in the Central Andes commonly have large radiocarbon reservoir effects. This, combined with the general scarcity of terrestrial organic matter, makes obtaining a reliable and accurate chronological model based on radiocarbon ages a challenge. As a result, age–depth models based on radiocarbon dating are often constructed by correcting for the modern reservoir effect, but commonly without consideration of spatial and possible temporal variations of reservoir ages within the lake and across the basin. In order to get a better constraint on the spatial variability of the radiocarbon reservoir effects, we analyse 14C ages of modern terrestrial and aquatic plants from the El Peinado basin in the southern Puna Plateau, which hosts Laguna del Peinado fed by hydrothermal springs. The oldest 14C ages of modern samples (>18000 and >26000 BP) were found in hot springs discharging into the lake, likely resulting from the input of 14C-depleted carbon from old groundwater and 14Cfree magmatic CO2. In the littoral and central part of Laguna del Peinado, 14C ages of modern samples were several thousand years younger (>13000 and >12000 BP) compared to the inflowing waters as a result of CO2 exchange with the atmosphere. Altogether, our findings reveal a spatial variability of up to 14000 14C years of the modern reservoir effect between the hot springs and the northern part of the Peinado lake basin. Temporal changes of reservoir effects in sediment records are more difficult to quantify, but 14C ages from a short core from Laguna del Peinado may suggest temporal reservoir age variations of a few thousand years. This study has implications for accurate 14C-based chronologies for palaeoclimate studies in the Altiplano–Puna Plateau and similar settings. Our results highlight the need to consider spatial and likely also temporal variations in the reservoir effects when constructing age–depth models.Fil: Vignoni, Paula A.. German Research Centre for Geosciences; AlemaniaFil: Cordoba, Francisco Elizalde. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Tjallingii, Rik. German Research Centre for Geosciences; AlemaniaFil: Santamans, Carla Daniela. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Lupo, Liliana Concepcion. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Brauer, Achim. German Research Centre for Geosciences; Alemani

Data set of dissolved major and trace elements from the lacustrine systems of Clearwater Mesa, Antarctica

This article presents analytical observations on physicochemical parameters and major and trace element concentrations of water, ice, and sediment samples from the lake systems of Clearwater Mesa (CWM), northeast Antarctic Peninsula. Geo-chemical analyses include inductively coupled plasma mass spectrometry (ICP-MS) for cations and trace elements and ion chromatography for anions. Some figures are included (i.e. Piper and Gibbs diagrams) which indicate water classification type and rock-water interactions in CWM, respectively. It also contains PHREEQC software output, listing the chemical speciation for dissolved elements, Saturation Indexes (SI), and modelling outputs. Each lake SI are also illustrated in a figure. Finally, total organic and inorganic carbon (TOC and TIC, respectively) were determined for bottom lake sediments and marginal salt samples. This information will be useful for future research assessing the impacts of anthropogenic pollution and the effects of climate change, providing insights into naturally occurring geochemical processes in a pristine environment, and evaluating geochemical behaviour of dissolved elements in high-latitude hydrological systems. These data correspond to the research article "Dissolved major and trace geochemical dynamics in Antarctic Lacustrine Systems" [1]. (C) 2020 The Authors. Published by Elsevier Inc

Dissolved major and trace geochemical dynamics in Antarctic lacustrine systems

Clearwater Mesa Uames Ross Island, northeast Antarctic Peninsula) provides a unique opportunity to study solute dynamics and geochemical weathering in the pristine lacustrine systems of a high latitude environment. In order to determine major controls on the solute composition of these habitats, a geochemical survey was conducted on 35 lakes. Differences between lakes were observed based on measured physico-chemical parameters, revealing neutral to alkaline waters with total dissolved solids (TDS) < 2500 mg L-1. Katerina and Trinidad-Tatana systems showed an increase in their respective TDS, total organic carbon values, and finner sediments from external to internal lakes, indicating an accumulation of solutes due to weathering. Norma and Florencia systems exhibited the most diluted and circumneutral waters, likely from the influence of glacier and snow melt. Finally, isolated lakes presented large variability in TDS values, indicating weathering and meltwater contributions at different proportions. Trace metal abundances revealed a volcanic mineral weathering source, except for Pb and Zn, which could potentially indicate atmospheric inputs. Geochemical modelling was also conducted on a subset of connected lakes to gain greater insight into processes determining solute composition, resulting in the weathering of salts, carbonates and silicates with the corresponding generation of clays. We found CO2 consumption accounted for 20-30% of the total species involved in weathering reactions. These observations allow insights into naturally occurring geochemical processes in a pristine environment, while also providing baseline data for future research assessing the impacts of anthropogenic pollution and the effects of climate change. (C) 2019 Elsevier Ltd. All rights reserved

Lacustrine systems of Clearwater Mesa (James Ross Island, north-eastern Antarctic Peninsula): Geomorphological setting and limnological characterization

Lentic freshwater habitats are important centres of biodiversity within the infrequent ice-free oases across Antarctica. Given imminent climate changes, it is crucial to catalogue these habitats in order to provide baseline data for future monitoring and biological surveys. The lacustrine systems of Clearwater Mesa, a previously unexplored part of James Ross Island, north-eastern Antarctic Peninsula, are described here. We conducted basic geomorphological and limnological surveys over three Antarctic summers (2009-16) to characterize landscape evolution, infer the origin of lake basins and assess the variability in their water chemistry. Stable shallow lakes, formed in depressions between lava tumuli following the last deglaciation, were found to dominate the volcanic mesa, although several peripheral lakes in ice-proximal settings appear to have formed recently as a result of post-Neoglacial ice recession. We found large heterogeneity in conductivity (~10-7000 μS cm-1), despite the lithologically uniform substrate. This variability was shown to be related to lake type, basin type (open vs closed), meltwater source and proximity to the coast. Inter-annual differences were attributed to changes in sea spray influx and snow accumulation driven by variable weather conditions. Overall, the ion composition of lakes suggested that sea spray was the dominant source of ions, followed by the weathering of bedrock.Fil: Roman, Matej. Charles University; República Checa. Masaryk University; República ChecaFil: Nedbalová, Linda. Charles University; República ChecaFil: Kohler, Tyler J.. Charles University; República ChecaFil: Lirio, Juan Manuel. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Coria, Silvia Herminda. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Kopácek, Jirí. Institute Of Hydrobiology, Biology Centre Of The Academy Of Sciences Of The Czech Republic; República ChecaFil: Vignoni, Paula A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Kopalová, Katerina. Charles University; República ChecaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Elster, Josef. University of South Bohemia; República ChecaFil: Nývlt, Daniel. Masaryk University; República Chec

Hydrological systems from the Antarctic Peninsula under climate change: James Ross archipelago as study case

Hydrological systems of the ice-free areas of the James Ross archipelago (NE Antarctic Peninsula) provide a unique opportunity for studying recent environmental changes associated with the current Global Warming. Geochemical, hydrological, sedimentological, and magnetic studies were carried out on different lake systems and ephemeral ponds from post-Holocene periglacial environments to characterize their natural variability. Significant differences between the lakes were observed based on physicochemical analyses, and can be attributed to several characteristics and processes taking place (geochemical,diagenetic, biological, etc.) in individual lake catchments. Seymour-Marambio Island?s lakes exhibit high total dissolved solids (*3.300 mg L-1) due to thehigh rate of evaporation in the region, whereas trace elements show differences in the lithological source. Lakes from Vega and James Ross islands are comparatively diluted, with the highest pH values up to 10.2. Within VegaIsland, trace elements discriminate lakes into sectors which show statistical differences due to variations in lithological sources. Dissolved sources can be divided according to their kinetics into: high-rate processes which occur duringsummer months (evaporation, salt precipitation, atmospheric precipitation, melting processes) and low-rate processes (mineral weathering, giving a long-term signature). The present multidisciplinary study contributes to abetter understanding of Antarctic lake systems, and can be used as a baseline dataset for further studies investigating the impact of recent climate changes on the biological and geochemical characteristics of these pristine ecosystems in the future.Fil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Vignoni, Ana Paz. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Cordoba, Francisco Elizalde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; ArgentinaFil: Chaparro, Marcos Adrián Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Kopalova, Katerina. Faculty Of Science, Department Of Ecology, University; República ChecaFil: Gargiulo, José Daniel. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Lirio, Juan Manuel. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Irurzun, Maria Alicia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Bohnel, Harald. Universidad Nacional Autónoma de México. Centro de Geociencias; Méxic

Magnetic parameters in paleolimnologicalstudies in Antarctica

En esta contribución se describen las distintas técnicas y mediciones magnéticas utilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útiles indicadores para realizar estudios relacionados con cambios climáticos y ambientales, así como herramientas de datación. Si bien es ampliamente conocida la utilidad de la susceptibilidad magnética, se discute el potencial y necesidad del uso de parámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes (natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos.Se presentan resultados magnéticos obtenidos en sedimentos lacustres del Archipiélago James Ross (NE de la Península Antártica). Se complementa con estudios sedimentológicos, hidroquímicos, geoquímicos y de estadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relación con los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analiza además el uso de las paleointensidades relativas como herramienta de datación en lagunas antárticas.Fil: Chaparro, Marcos Adrián Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Gargiulo, José Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones En Física E Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Iruzun, María A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones En Física E Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Chaparro, Mauro Alejandro Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones En Física E Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: Böhnel, Harald N.. Universidad Nacional Autonoma de Mexico. Centro de Geociencias; MéxicoFil: Cordoba, Francisco Elizalde. Centro de Investigación y Transferencia de Jujuy. Instituto de Geología y Minería; ArgentinaFil: Vignoni, Paula A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: Manograsso Czalbowski, Nadia T.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Lirio, Juan M.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Nowaczyk, Norbert. GeoForschungsZentrum Potsdam; AlemaniaFil: Sinito, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones En Física E Ingeniería del Centro de la Provincia de Buenos Aires; Argentin