| Abstract | Lakes are ideal sites to study environmental changes since they preserve climatic, anthropogenic, and volcanic signals in their sediments. Brazo Blest is one of the most important ramifications of Lake Nahuel Huapi and it is an interesting site to study climatic variations as it receives direct discharge of heavy suspended sediments loads from Tronador Glacier through the Frías River, as a result of the abrasion of the bedrock and runoff from the surrounding Valdivian Forest. A short sediment core from Brazo Blest was analyzed for chironomid and diatom assemblages and pigments in order to reconstruct environmental changes during the last 100 years in the basin under study. This multiproxy study also included geochemical and physical analyses and reveals changes in the productivity of the lake over time, showing a shift in the 1950s from autochthonous to allochthonous organic matter. This modification is related to the increase of precipitation and the consequent fluvial runoff from two catchments, Frías River and the Blest-Cántaros basin together with the effects ofrising temperatures, which affected Tronador Glacier. Further, it allows us to link volcanic eruptions to a decrease in species richness and number of chironomids and diatoms, as a consequence of reduced light intensities and food availability induced by the high content of suspended sediments in the water column. This study highlights the effectiveness of multiproxy analyses to reconstruct environmental changes. Key words. Chironomids. Diatoms. Pigments. Lake sediments. Paleoenvironmental reconstruction. Patagonia. |
| Text | 347636 2016 10.5710/AMGH.14.09.2015.2912 ISI Web of Science WOS 000372367400006 Chironomids. Diatoms. Pigments. Lake sediments. Paleoenvironmental reconstruction. Patagonia LITTLE ICE AGE TO PRESENT PALEOENVIRONMENTAL RECONSTRUCTION BASED ON MULTYPROXY ANALYSES FROM NAHUEL HUAPI LAKE PATAGONIA, ARGENTINA . M. NOEL SERRA1, M. LUJÁN GARCÍA2, NORA MAIDANA1,2, GUSTAVO VILLAROSA4,5, ANDREA LAMI3, AND JULIETA MASSAFERRO1 1CENAC, Programa de Estudios Aplicados a la Conservacion del Parque Nacional Nahuel Huapi Concejo Nacional de Investigaciones Cientificas y Tecnicas CONICET Administracion de Parques Nacionales APN , Fagnano 244, R8400BCL San Carlos de Bariloche, Rio Negro, Argentina. marianoelserra@gmail.com; julimassaferro@hotmail.com 2Laboratorio de Diatomeas Continentales, Departamento de Biodiversidad y Biologia Experimental DBBE , Facultad de Ciencias Exactas y Naturales FCEN Universidad de Buenos Aires UBA ; Instituto de Biodiversidad y Biologia Experimental y Aplicada IBBEA Universidad de Buenos Aires UBA Concejo Nacional de 1 Investigaciones Cientificas y Tecnicas CONICET , Ciudad Universitaria, Pabellon 2, CABA, Argentina. a.lami@ise.cnr.it; nim@bg.fcen.uba.ar 3 Consiglio Nazionale delle Ricerche CNR Istituto per lo Studio degli Ecosistemi ISE ; Pallanza Verbania, Italy. a.lami@ise.cnr.it 4 Instituto de Investigaciones de Biodiversidad y Medio Ambiente INIBIOMA , Concejo Nacional de Investigaciones Cientificas y Tecnicas CONICET , Argentina.gvillarosa@gmail.com 5 Universidad Nacional del Comahue, Quintral 1250, R8400FRF San Carlos de Bariloche, Argentina. Lakes are ideal sites to study environmental changes since they preserve climatic, anthropogenic, and volcanic signals in their sediments. Brazo Blest is one of the most important ramifications of Lake Nahuel Huapi and it is an interesting site to study climatic variations as it receives direct discharge of heavy suspended sediments loads from Tronador Glacier through the Frias River, as a result of the abrasion of the bedrock and runoff from the surrounding Valdivian Forest. A short sediment core from Brazo Blest was analyzed for chironomid and diatom assemblages and pigments in order to reconstruct environmental changes during the last 100 years in the basin under study. This multiproxy study also included geochemical and physical analyses and reveals changes in the productivity of the lake over time, showing a shift in the 1950s from autochthonous to allochthonous organic matter. This modification is related to the increase of precipitation and the consequent fluvial runoff from two catchments, Frias River and the Blest Cantaros basin together with the effects ofrising temperatures, which affected Tronador Glacier. Further, it allows us to link volcanic eruptions to a decrease in species richness and number of chironomids and diatoms, as a consequence of reduced light intensities and food availability induced by the high content of suspended sediments in the water column. This study highlights the effectiveness of multiproxy analyses to reconstruct environmental changes. Key words. Chironomids. Diatoms. Pigments. Lake sediments. Paleoenvironmental reconstruction. Patagonia. Resumen. RECONSTRUCCIÓN PALEOAMBIENTAL DESDE LA PEQUEÑA EDAD DEL HIELO HASTA EL PRESENTE BASADA EN ANALISIS MULTIPROXY DEL LAGO NAHUEL HUAPI PATAGONIA, ARGENTINA . Los lagos son sitios ideales para estudiar los cambios ambientales, ya que en sus sedimentos se preservan señales climaticas, antropogenicas y volcanicas. El Brazo Blest es uno de los brazos mas importantes del Lago Nahuel Huapi y es un sitio interesante para estudiar variaciones climaticas, ya que recibe la descarga directa de sedimentos en suspension desde el Glaciar Frias, a traves del rio homonimo. Estos sedimentos se originan a partir de la abrasion glaciaria, y de la erosion fluvial del sustrato en los ambientes de selva valdiviana circundante. Se analizaron los ensambles de quironomidos y diatomeas, asi como los pigmentos, de un testigo corto obtenido en el Brazo Blest, para reconstruir los cambios ambientales ocurridos en los ultimos 100 años en la cuenca bajo estudio. Este estudio multiproxy tambien incluyo analisis geoquimicos y fisicos, revelando variaciones en la productividad del lago, mostrando un cambio en el origen de la materia organica, pasando de autoctona a aloctona, ocurrido en los 1950s. Este cambio se relaciona con aumentos en las precipitaciones y escorrentia de la cuenca del Rio Frias y de la Cuenca Blest Cantaros, ademas del incremento en las temperaturas que afecto a los glaciares del Tronador. Asimismo, esto nos permitio asociar eventos volcanicos con un descenso en la abundancia y riqueza especifica de quironomidos y diatomeas, atribuidos al aporte de sedimentos en suspension en la columna de agua, produciendo una disminucion de la intensidad de la luz y reduccion de la disponibilidad de alimentos. Este estudio resalta la efectividad de realizar analisis multiproxy para reconstruir cambios ambientales pasados. 53 Published version http //www.ameghiniana.org.ar/index.php/ameghiniana/article/view/1043 14/09/2015 Articolo in rivista Asociacion Paleontologica Argentina 0002 7014 Ameghiniana Ameghiniana Ameghiniana andrea.lami LAMI ANDREA |
