Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/53495
Title: Diatom-based reconstruction of Late Glacial and Early Holocene environment in the Pyrenees = Reconstrucción ambiental del Tardiglaciar y el Holoceno Temprano en los Pirineos utilizando el registro sedimentario de diatomeas
Author: Rivera Rondón, Carlos Alberto
Director: Catalan i Aguilà, Jordi
Keywords: Diatomees
Holocè
Pirineus
Paleobiologia
Ecologia dels llacs
Diatoms
Holocene
Pyrenees
Paleobiology
Lake ecology
Issue Date: 20-Feb-2014
Publisher: Universitat de Barcelona
Abstract: [spa] Los lagos son ecosistemas expuestos a la influencia combinada del clima y la entrada de materiales y nutrientes desde la cuenca. La información de estos procesos y de la dinámica interna del sistema suele archivarse en los sedimentos mediante la acumulación de los materiales externos y los producidos por el sistema. Dentro de los materiales acumulados en los sedimentos, las valvas de diatomeas pueden aportar información limnológica que es difícil de obtener con otros indicadores. El objetivo principal de esta tesis fue explorar el potencial de las diatomeas para realizar reconstrucciones ambientales multivariadas del pasado, con una aplicación a la secuencia sedimentaria del Holoceno Temprano y el Tardiglaciar del lago Burg (Pirineos). La variabilidad regional de la distribución de diatomeas en zonas alpinas y templadas es generalmente explicada por el gradiente de pH y alcalinidad. Sin embargo, existe una gran variabilidad que está relacionada con otros factores ambientales y que podría también ser utilizada en el desarrollo de la reconstrucción del ambiente acuático. Algunos autores ponen en duda la viabilidad de realizar reconstrucciones independientes, utilizando un único registro de diatomeas, argumentando que la correlación entre las variables puede alterar las señales que son reconstruidas. Sin embargo, otros autores sostienen que es posible realizar reconstrucciones, si existen conjuntos de especies con respuestas distintas. De acuerdo con esto, inicialmente se realizó un estudio taxonómico y ecológico de las diatomeas de 80 lagos de montaña de los Pirineos. Se exploraron los factores ambientales que, además del pH, explican la distribución de diatomeas en los lagos pirenaicos, incluyendo factores próximos al lago y descriptores generales de la cuenca. Este análisis se realizó siguiendo la aproximación de especies indicadoras. Así mismo, se desarrollaron funciones de transferencia para reconstruir diferentes variables independientes a partir de un mismo conjunto de datos de diatomeas. Posteriormente, se aplicaron los resultados las especies indicadoras y las funciones de transferencia en la secuencia sedimentaria del lago Burg cubriendo el Tardiglaciar y el Holoceno Temprano. Finalmente, se analizan los resultados encontrados en términos de los procesos internos del lago y su eventual vinculación con procesos relacionados con el clima y la cuenca.
[eng] Lakes are ecosystems exposed to the combined influence of climate and catchment processes. Lakes collect and archive evidence of these forcings in their sediments through of a complex interaction with internal processes. Deciphering and extracting information from the sediments is a challenging task because, in addition to the inter-dependence between the forcing agents, the lake ontogeny affects the way in which the system responds to them. Among the sub-fossil material, diatoms occupy an outstanding position. The remains can be identified to the species level, due to the siliceous composition of their valves. This fact, added to the rich community that at any instant exists in the lake, make diatoms an excellent proxy for environmental reconstructions. In this study, the focus is placed on the diatom assemblages of the lakes of the Pyrenees and their potential as indicators of environmental conditions. The findings are applied to the sedimentary sequence of the former Burg Lake to reconstruct the lake conditions during Late Glacial and early Holocene periods. The regional variability of diatom distributions is usually explained by pH or acid neutralising capacity gradients in alpine and temperate areas. However, there is a large remaining unexplained variability, which is related to other environmental factors, and could be also used in environmental reconstructions. Some researchers question the feasibility of independent reconstructions of several variables from a single diatom record; they argue that the high temporal autocorrelation of the local assemblages might obscure secondary influences. However, some others sustain that it is possible to perform reconstructions, even of particularly dependent variables if they present contrasting trends at some sites. Accordingly, it was carried out an extensive taxonomical study of diatom of the mountain lakes of the Pyrenees. After this, were explored the environmental factors that, besides pH, explains the diatom distribution in the lakes of the Pyrenees, including in-lake proximal factors as well as general descriptors of catchment characteristics and using indicator analysis approach. In order to demonstrate that it is possible to reconstruct different independent variables from a unique diatom data set were developed transfer functions for selects variables and analysed the reliability and the independence of models performed. The analysis was carried out by comparing the performance of two sample data-sets (bottom surface sediment and epilithon samples). The ratio between Chrysophycean cysts and diatoms was analysed as a potential environmental indicator. Indicator species and the transfer functions were applied to the diatoms of the sedimentary sequence of Burg Lake covering Late Glacial and Early Holocene. The reconstructed variables were analysed in terms of in-lake processes and their eventual link with climate and catchment processes. An interpretation of the reconstruction of climate during Late Glacial and Early Holocene in the Pyrenees is shown.
URI: http://hdl.handle.net/2445/53495
Appears in Collections:Tesis Doctorals - Facultat - Biologia

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