Ultra-high resolution environmental and climatic reconstruction using oxygen and carbon isotopes of diatom frustules

[eng] Calcareous microfossils are not always present in marine or lacustrine sediments owing to unfavourable ecological or post-depositional conditions. These non-carbonated sediments sometimes contain abundant biogenic silica, rendering them suitable for studies of stable isotopes. For this reason, considerable progress has been made in the study of biogenic silica using isotopes in recent years. Diatom isotopes are increasingly being used for palaeoenvironmental reconstructions in lacustrine sedimentary records. Tropical proxy records offer valuable insights into past climate and environmental changes of the Earth and into possible future climate change scenarios. Research into tropical regions has therefore become a key issue among palaeoclimatologists. Influenced by the tropical circulation in the north, and by the mid-latitude westerlies in the south, the Central Andes are an ideal site to study past variations of atmospheric circulation systems. Thus, the Andean Altiplano has become a key region for the study of late Quaternary climate change in South America. Sedimentary records of high-altitude Andean Altiplano lakes usually preserve an excellent centennial- to millennial-scale record of effective moisture fluctuations and source changes during the Late Glacial and Holocene despite the fact that the interpretation is not always straightforward. Oxygen and carbon isotope analyses in carbonates (δ18Ocarbonate and δ13Ccarbonate) and δ13Cbulk have been successfully used to reconstruct the hydrological responses to climate change in different Andean lacustrine systems to date. No attempt, however, has been made to use δ18Odiatom and δ13Cdiatom despite the fact that they are usually the best preserved fossils in the sedimentary record of the Andean Altiplano lakes. For this reason, the aims of the PhD Thesis are twofold: a) to explore the possibilities that the study of δ18Odiatom and δ13Cdiatom can offer in palaeoenvironmental reconstructions, and b) to carry out high- and ultra-high resolution environmental and climate reconstructions in the Andean Altiplano during the Late Glacial- Early Holocene transition using these stable isotopes. The thesis focuses on new and poorly documented fields where δ18Odiatom and δ13Cdiatom can successfully be applied to lacustrine sediments. It shows how stable isotopes from diatom silica may be used a) to highlight the importance of reconstructing the different evolutionary stages of lake ontogeny given that climate derived palaeohydrological signals can be distorted by changes in lake morphology b) as a main proxy in ultra-high resolution moisture balance reconstructions forced by fluctuations in the intensity of the ENSO and solar activities c) to reveal the major biogeochemical processes that give rise to the formation of rhythmites, and finally d) to reconstruct the regional environmental evolution at centennial-to-millenial time scales.[spa] La tesis está basada en la reconstrucción ambiental y climática a muy alta resolución mediante los sedimentos laminados y ricos en diatomeas de un lago tropical situado en los Andes Centrales. Para la reconstrucción se ha utilizado la novedosa técnica del análisis de isótopos estables (δ18Odiat y δ13Cdiat) de la sílice de las diatomeas. Los principales resultados y conclusiones son: Diversos factores ambientales pueden influir en los valores de δ18Odiat. Los registros de δ18Odiat en sistemas lacustres cerrados no pueden ser simplemente interpretados en términos de seco o húmedo, sino que es imperativo entender la hidrología y geomorfología de cada sistema antes de hacer una interpretación de tipo estrictamente climático como se había hecho hasta la fecha. Por su parte, los análisis de δ13Cdiat han demostrado que esta técnica es una herramienta válida para realizar reconstrucciones del ciclo del carbono en los lagos, así como para dar un mejor punto de vista del ciclo del carbono a nivel global. La unidad sedimentaria laminada del Lago Chungará está formada por ritmitas multianuales compuestas por láminas de color blanco y verde. Estás láminas son ricas en diatomeas y son el resultado de diferentes procesos lacustres. Las láminas de claras se formaron como consecuencia de «blooms» extraordinarios de muy corta duración (días o semanas). Las láminas oscuras se depositaron a lo largo de diversos años bajo diferentes condiciones de la columna de agua y por tanto representan las condiciones de base del lago. Los valores de δ18Odiat muestran que los «blooms» extraordinarios fueron más intensos con condiciones de bajo nivel del lago, mientras que la formación de láminas oscuras se vio especialmente inducida por subidas del nivel. Al mismo tiempo, los valores de δ13Cdiat indican que la disponibilidad de carbono fue superior durante los «blooms» extraordinarios de diatomeas. La combinación de los dos registros ha destacado les complejas relaciones entre los procesos limnológicos, los procesos de la cuenca de drenaje, la hidrología y los forzamientos climáticos. El registro de isotopía expone claramente que, según la escala temporal, un tipo de proceso puede dominar sobre los otros en la interpretación de la isotopía

Reconciling North Atlantic climate modes: revised monthly indices for the East Atlantic and the Scandinavian patterns beyond the 20th century

Climate variability in the North Atlantic sector is commonly ascribed to the North Atlantic Oscillation. However, recent studies have shown that taking into account the second and third mode of variability (namely the East Atlantic – EA – and the Scandinavian – SCA – patterns) greatly improves our understanding of their controlling mechanisms, as well as their impact on climate. The most commonly used EA and SCA indices span the period from 1950 to present, which is too short, for example, to calibrate palaeoclimate records or assess their variability over multi-decadal scales. To tackle this, here, we create new EOF-based (empirical orthogonal function) monthly EA and SCA indices covering the period from 1851 to present, and compare them with their equivalent instrumental indices. We also review and discuss the value of these new records and provide insights into the reasons why different sources of data may give slightly different time series. Furthermore, we demonstrate that using these patterns to explain climate variability beyond the winter season needs to be done carefully due to their non-stationary behaviour. The datasets are available at 10.1594/PANGAEA.892769

FIANZAS. EL ARBITRAJE EN LAS AGENCIAS DE VIAJE

      The present study will be dealing with the different types of bond which travel agencies are obligued to provide: either all or sundry, as a guarantee or as a policy, etc. It will also deal with the extent to which such guarantees are responsible as well as the different circumstances in which they can be applied.       The second part of this report will be focused on arbitration in the travel agency, especifically regarding the commercial arbitration which is currently applicable to travel agencies, as well as a deep analysis of the Real Decreto (Royal Decree) 636/1993 which regulates it.      En este trabajo se estudian las fianzas que las AAVV deben prestar de forma obligatoria, ya sean individuales o colectivas, o revistan la forma de aval, póliza de caución, etc. Se examinan igualmente cuál es el ámbito de responsabilidad de dichas garantías y los distintos supuestos de ejecución.       En la segunda parte, se analiza el arbitraje en las AAVV, especialmente en lo que atañe al sistema arbitral de consumo que en la actualidad les es aplicable, así como un somero análisis del Real Decreto 636/1993 que lo regula

ESTADÍSTICAS DE DEMANDA TURÍSTICA EN LA REGIÓN DE MURCIA

     The survey confirms an evident statistic deficit concerning the tourist demand in the Region of Murcia. However, Regional Tourist law envisages the fulfiment of a Regional Statistic Plan not yet designed, but which will have to be used in order to improve this situation. The present situation stems from the lack of an statistic regional service in the State Tourism Office. The reason for this lack is probably the scanty budget of this organization. Not only the official institutions but also the business companies lack enough information about the matter in question, although some important surveys are worth standing out because of their accurancy, but they have a problem related to their lack of contituity in the time. Next, we deal thoroughly with the statistic system on tourism which have been introduced by the European Community, the Spanish Government and some Autonomous Communities, such as Andalucia & Galicia.     El estudio constata un evidente déficit estadístico en materia de demanda turística en la Región de Murcia. No obstante, la Ley Regional de Turismo prevé la realización de un Plan Regional de Estadísticas que debe aprovecharse para corregir esta situación. La situación actual deriva de la ausencia de un servicio regional de Estadísticas en la propia Dirección General de Turismo cuya causa parece ser el exiguo presupuesto de este organismo. No sólo los organismos oficiales sino también asociaciones empresariales carecen de información suficiente sobre la materia, aunque son de destacar importantes estudios, elaborados con rigor pero que presentan el problema de su falta de continuidad en el tiempo. Se estudian a continuación los sistemas estadísticos sobre turismo que se han implantado por la UE, el Estado español y algunas Comunidades Autónomas, como Andalucía y Galicia, concluyendo en la conveniencia de adoptar la metodología andaluza (ECTA, IEA), debidamente depurada y adaptada a las necesidades regionales

Influencia de la adición de taninos enológicos en el color del vino

Los taninos son importantes componentes de la calidad del vino, ya que contribuyen tanto a la percepción en boca como a la estabilización del color con el tiempo. A su vez, el color es sin lugar a dudas uno de los aspectos organolépticos más importantes de un vino. Es por ello que la adición de taninos enológicos para mejorar las características de los vinos tintos es una práctica muy extendida en bodegas durante la elaboración de vinos tintos. Sin embargo, son muy pocos los estudios realizados en este campo y así mismo existe controversia en las opiniones de diferentes autores en cuanto a si esta adición es efectiva o no. El objetivo de este proyecto es determinar la influencia de la adición de taninos enológicos de Quebracho y de uva en el color del vino tinto. Para ello se elaboraron vinos a partir de uvas de las variedades tempranillo y garnacha procedentes de la D.O. Rioja. De cada vino se prepararon dos controles, dos muestras con tanino de Quebracho añadido en la fase pre-fermentativa y dos muestras con tanino de Quebracho y tanino de uva añadidos en la fase pre-fermentativa y post-fermentativa respectivamente. Se realizaron análisis de color y de compuestos fenólicos: intensidad de color, índice de polifenoles totales y concentración de taninos y antocianos totales en distintas etapas de la vinificación: al finalizar la fermentación alcohólica, al finalizar la fermentación maloláctica y tras la adición de SO2. Los datos fueron estudiados mediante análisis de varianza (ANOVA). Los resultados indican que la adición combinada de tanino de Quebracho y tanino de uva afecta positivamente a la intensidad del color. No obstante la adición única de tanino de Quebracho en las cantidades recomendadas por el fabricante no contribuye a la mejora de la intensidad de color. Esto sugiere que adición de taninos enológicos puede estar en muchos casos injustificada

Comment on "Climate in the Western Cordillera of the Central Andes over the last 4300 years", by Engel et al. (2014)

Engel et al. (2014) present a new approach to understand Holocene climate changes in the Central Andes. They reconstruct the relative temperature changes in the Western Cordillera for the last 4,300 years by characterizing the 13C composition of a plant species occurring in the Carhuasanta peat sedimentary record (Peru, 15º 30' S

Unraveling the Holocene Eruptive History of Flores Island (Azores) Through the Analysis of Lacustrine Sedimentary Records

Lacustrine sequences from active volcanic settings usually hold a rich and continuous record of tephra layers, providing a critical source of information to reconstruct a most complete eruptive history of a region. Lake sedimentary records on volcanic islands are particularly useful as the typical small size of these islands and their steep subaerial and submarine slopes lead to a lower preservation of potential erodible pyroclastic deposits. Here we explore the lacustrine sedimentary record of Lagoa da Lomba, a crater lake in the central upland area of Flores Island (Azores), to gain insight into the recent eruptive history of this island. The strategic location of Lagoa da Lomba, half distance between the two clusters of recent volcanic activity of the island, together with its long-lasting record, back to 23.52 cal kyr BP, makes this lake a privileged site to investigate the Holocene volcanic history of Flores. Based on a detailed stratigraphic characterization of sediments from a lake transect of three cores, supported by glass shard geochemistry and radiocarbon dating, we recognized four Holocene eruptive events taking place between 6.28 and 2.36 cal kyr BP, demonstrating that the Holocene volcanic activity at Flores Island may have lasted longer than previously reported. Glass shard geochemistry from the different tephra layers suggests three populations, basaltic to trachybasaltic in composition, where the last eruption is the least evolved endmember. Two of the four eruptive events correlate with subaerially-exposed pyroclastic sequences, in terms of stratigraphy and geochemistry. The most recent event recorded at Lagoa da Lomba was constrained to 3.66 - 2.36 cal kyr BP and linked to an eruption sourced from Lagoa Comprida Volcanic System. The second most recent eruptive event was sourced from Lagoa Funda Volcanic System and dated at 3.66 cal kyr BP. Our observations show that Flores experienced vigorous volcanic activity during the Late Holocene. Therefore, contrary to what is assumed, the possibility of future eruptions should be properly considered, and the volcanic hazard here should not be underestimated. Moreover, we highlight the importance of tephrostratigraphy in recent lake sediments to reconstruct past volcanic activity, especially at small volcanic islands, such as Flores, where exposure is poor due to erosion within the limited subaerial area and the dense vegetation

Formation and evolution of back-barrier perched lakes in rocky coasts: an example of a Holocene system in NW Spain

Coastal back-barrier perched lakes are freshwater bodies that are elevated over sea-level and are not directly subjected to the inflow of sea-water. This study provides a detailed reconstruction of the Doniños back-barrier perched lake that developed at the end of a small river valley in the rocky coast of the northwest Iberian Peninsula during the Holocene transgression. Its sequence stratigraphy was reconstructed based on a core transect across the system, the analyses of its lithofacies and microfossil assemblages, and a high-resolution radiocarbon-based chronology. The Doniños perched lake was formed ca. 4.5 ka BP. The setting of the perched lake was favoured by Late Holocene sea-level stabilization and the formation of a barrier and back-barrier basin, which was contemporaneous with the high systems tract period. This basin developed over marine and lagoonal sediments deposited between 10.2 and 8.0 ka BP, during rapidly rising sea-level characteristic of the transgressive systems track period. At 1.1 ka BP, the barrier was breached and the perched lake was partially emptied, causing the erosion of the back-barrier basin sediments and a significant sedimentary hiatus. Both enhanced storminess and human intervention were likely responsible for this event. After 1 ka BP, the barrier reclosed and the present-day lake was reformed, with the water level reaching as high as 5 m amsl. The depositional evolution of the Doniños system serves as a model of coastal back-barrier perched lakes in coastal clastic systems that have developed over gently seaward-dipping rugged substrates at small distances from the shoreline and under conditions of rising sea-level and high sediment supply. A review of estuaries, back-barrier lagoons, pocket beaches and back-barrier perched lakes in the rocky coast of the northwest Spain shows that the elevation of the bedrock is the main factor controlling the origin and evolution of these systems

Dinámica de los sistemas dunares costeros ante el Cambio Global: La necesidad de una gestión sostenible

El desarrollo y evolución de los sistemas arenosos costeros está gobernado por un frágil equilibrio dinámico entre la interacción de múltiples factores ambientales, y por ello estos sistemas naturales son altamente sensibles a las perturbaciones humanas. Estas alteraciones se acentúan en el contexto actual de Cambio Global. Los cambios en los vientos, en el oleaje, en la intensidad de las tormentas, en la disponibilidad de arena y en la vegetación juegan un papel crucial en el complejo desarrollo de las dunas, tanto por retener la arena que forma las dunas, como para protegerlas físicamente de la erosión. Actualmente, muchos de los ecosistemas dunares se encuentran degradados sobre todo por el déficit de aportes sedimentarios y la presión sobre la cubierta vegetal, fenómenos siempre muy relacionados con el impacto antrópico. El desarrollo natural de los sistemas dunares, incluida su vegetación, contribuye de forma significativa a amortiguar los efectos destructivos de los eventos climáticos extremos, incrementados durante el actual periodo de Cambio Global. Así, las dunas costeras suponen un patrimonio natural muy valioso que debe ser conservado. Aquí presentamos un trabajo de revisión sobre el estado del arte y una síntesis de factores y procesos de cara a un nuevo enfoque en la gestión costera. Al mismo tiempo, en este artículo se defiende una gestión que no interrumpa los procesos geomorfológicos que intervienen en el desarrollo natural del ecosistema dunar, y que son el soporte principal de su biodiversidad. Se demuestra que, a medio y largo plazo, una gestión respetuosa con la dinámica geológica dunar favorece tanto el mantenimiento de la biodiversidad como la conservación del paisaje costero y sus servicios ecosistémicos

Climatic and lacustrine morphometric controls of diatom paleoproductivity in a tropical Andean lake

15 páginas, 6 figuras, 1 tablaThe coupling of lake dynamics with catchment biogeochemistry is considered the key element controlling primary production in mountain lakes at time scales of a few decades to millennia, yet little is known on the impacts of the morphometry of lakes throughout their ontogeny. As Lake Chungará (Central Andean Altiplano, northern Chile) experienced long-term lake-level fluctuations that strongly modified its area:volume ratio, it is an ideal system for exploring the relative roles that long-term climatic shifts and lake morphometry play on biosiliceous lacustrine productivity. In this paper, we review previous data on the percent contents of total organic carbon, total inorganic carbon, total nitrogen, total biogenic silica, isotopic composition of organic matter, carbonates, and diatom frustules, as well as data on the abundance of the chlorophycean Botryococcus braunii in this lake for the period 12,400–1300 cal yr BP. We also include new data on organic carbon and biogenic silica mass accumulation rates and the diatom assemblage composition of an offshore core dated using 14C and U/Th. Biosiliceous productivity in Lake Chungará was influenced by shifts in allochthonous nutrient inputs related to variability in precipitation. Humid phases dated at approx. 12,400 to 10,000 and 9600 to 7400 cal yr BP coincide with periods of elevated productivity, whereas decreases in productivity were recorded during arid phases dated at approx. 10,000 to 9600 and 7400 to 3550 cal yr BP (Andean mid-Holocene Aridity Period). However, morphometry-related in–lake controls led to a lack of a linear response of productivity to precipitation variability. During the late Glacial to early Holocene, lowstands facilitated complete water column mixing, prompting episodic massive blooms of a large centric diatom, Cyclostephanos cf. andinus. Thus, moderate productivity could be maintained, regardless of aridity, by this phenomenon of morphometric eutrophy during the early history of the lake. The subsequent net increase in lake level introduced modifications in the area of the epilimnion sediments versus the total volume of the epilimnion, preventing complete overturn. Surpassing a certain depth threshold at approx. 8300 cal yr BP caused cessation of the morphometric eutrophy conditions associated with Cyclostephanos cf. andinus superblooms. After 7300 cal yr BP, the lake experienced a decrease in biosiliceous productivity and a change of state that involved a stronger dependence on precipitation variability, with a lesser contribution of diatoms to the total primary productivity. Our results show that the interpretation of lacustrine paleoproductivity records as paleoclimatic archives needs to take into account the effects of changes in the epilimnion sediment area to epilimnion volume ratio in association with lake ontogenyThe Spanish Ministry of Science and Innovation funded this research through the projects ANDESTER (BTE2001-3225), Complementary Action (BTE2001-5257-E), LAVOLTER (CGL2004-00683/BTE), GEOBILA (CGL2007-60932/BTE) and CONSOLIDER-Ingenio 2010 GRACCIE (CSD2007-00067)Peer reviewe