1,721,061 research outputs found
Echoes of macaronesian vegetation : 3 archipelagos, 3 stories. A palaeoecological analysis through vegetation, charcoal and spores
No full textArchaeological and palaeoecological studies provide abundant evidence for both the magnitude of human impact and the speed at which it can occur on islands worldwide (Burney, 1997; Rick et al., 2013; Braje et al., 2017). This study analyzes palaeoecological data from nine islands across three Macaronesian archipelagos - the Azores, Cabo Verde, and the Canary Islands - to explore vegetation changes over time in relation to the timing and nature of human colonization on each island
Lake Sanabria ecosystem regime shift (1986-2019) [Dataset]
No full textThis dataset has been used to study the ecosystem regime shifts of Lake Sanabria, the largest natural glacial lake in Spain, in a situation of climate change that may affect compliance with ecological quality objectives, even with no significant water quality pressures. It comprises basic data from long-term (1986-2017) and intensive short-term (2015-2017) limnological monitoring of a few relevant state variables related to nutrients balance, primary production of phytoplankton and thermal structure of the water column. Data about recent history of the lake productivity, reconstructed by high-resolution palaeolimnological analysis of a surface sediment core, is provided. Time series analysis over several decades has detected significant conditional heteroscedasticity in the concentrations of parameters such as chlorophyll and oxygen in recent years in relation to lake turnover rates, coinciding with exceptional episodic single-species blooms of some planktonic diatoms. We include precipitation data, inflow measurements and land use modeling data that indicate how external nutrient loadings have declined during the last decades, with reduced precipitation and progressive afforestation of the catchment, but the lake is shifting to a more productive regime enhancing the relevance of internal loading and processes.Confederación Hidrográfica del Duero : 452-A-640.01.01/2014Peer reviewe
El Misteri de l'Illa de Decepció resolt. La major erupció en els darrers mil·lennis que ha sotragat l'Antàrtida
No full textEls anàlisis dels sediments lacustres de la Península de Byers han permès resoldre la data de l'erupció més gran dels darrers mil·lennis a l'Antàrtida: fa 3.980 anys. Aquesta erupció va formar la caldera del volcà de l'Illa Decepció i va ser origen de la particular forma de ferradura característica de l'Illa. De fet, el volum de roca ejectada va ser tan gran que és comparable al de la gran erupció del volcà Tambora l'any 1815.Los análisis de los sedimentos lacustres de la Península de Byers han permitido resolver la fecha de la mayor erupción de los últimos milenios en la Antártida: hace 3.980 años. Esta erupción formó la caldera del volcán de la Isla Decepción y fue origen de la particular forma de herradura característica de la Isla. De hecho, el volumen de roca eyectada fue tan grande que es comparable al de la gran erupción del volcán Tambora en 1815.3,980 years ago occurred the largest eruption of the last millennia in Antarctica, according to the latest analysis of the lake sediments on the Byers Peninsula. This eruption formed the Deception Island volcanic caldera, which is the origin of the characteristic shape of a horseshoe of the Island. In fact, the volume of rock erupted was so large that it is comparable to the great eruption of the Tambora volcano in 1815
El Misteri de l'Illa de Decepció resolt. La major erupció en els darrers mil·lennis que ha sotragat l'Antàrtida
No full textEls anàlisis dels sediments lacustres de la Península de Byers han permès resoldre la data de l'erupció més gran dels darrers mil·lennis a l'Antàrtida: fa 3.980 anys. Aquesta erupció va formar la caldera del volcà de l'Illa Decepció i va ser origen de la particular forma de ferradura característica de l'Illa. De fet, el volum de roca ejectada va ser tan gran que és comparable al de la gran erupció del volcà Tambora l'any 1815.Los análisis de los sedimentos lacustres de la Península de Byers han permitido resolver la fecha de la mayor erupción de los últimos milenios en la Antártida: hace 3.980 años. Esta erupción formó la caldera del volcán de la Isla Decepción y fue origen de la particular forma de herradura característica de la Isla. De hecho, el volumen de roca eyectada fue tan grande que es comparable al de la gran erupción del volcán Tambora en 1815.3,980 years ago occurred the largest eruption of the last millennia in Antarctica, according to the latest analysis of the lake sediments on the Byers Peninsula. This eruption formed the Deception Island volcanic caldera, which is the origin of the characteristic shape of a horseshoe of the Island. In fact, the volume of rock erupted was so large that it is comparable to the great eruption of the Tambora volcano in 1815
Organic geochemical analysis of sediment cores from Lake Funda (Azores Archipelago, Portugal)
No full textTo evaluate changes in terrestrial and aquatic ecosystems in the Azores, we developed paleoecological and paleoclimate records from Lake Funda on Flores Island that span the last millennium. Vegetation composition (n-alkane average chain length) indicate when human activities began in the catchment area and biogenic silica tracks changes in diatom productivity. In addition, sterol hydrogenation and archaeal lipids (isoprenoid glycerol dialkyl glycerol tetraethers) trace changes in redox conditions and biogeochemical cycles, respectively. Finally, a high-resolution reconstruction using leaf wax hydrogen isotopes records changes in precipitation amount over the last millennium
Using paleolimnology to find restoration solutions: the case of Lake Muzzano, Switzerland
No full textLake Muzzano (45°59′50″N 8°55′41″E, 337 m a.s.l.) is a hyper-eutrophied lake located in the Tessin region of Switzerland. Almost every year, algal blooms (Microcystis) cover the lake with a thickness of 1–2 cm. These blooms associated with periods of anoxia in summer have led to fish kills in 1967 and 1994. In the hope of avoiding these blooms, a bypass bringing water away from the lake has been established in 1999. This solution was not adequate as blooms kept reoccurring. Sediment removal was then proposed by the Tessin Canton as a possible remediation technique and The L.A.K.E.S Institute had a mandate in 2010 to study the lake (present and past state) to determine the reasons creating anoxia and algal blooms. The present state of the lake shows that anoxia is still occurring when the algal bloom covers the lake's surface. Subfossil diatom and chironomid analyses show that the baseline conditions were those found before 1922 AD when the lake was oligotrophic and supported a diversified community of chironomids suggesting good oxygenation. After 1922 AD, circulation to the lake was cut out and nutrients accumulated in the lake leading to anoxia and the establishment of Microcystis. Heavy metal analysis in the sediment shows that the concentration is above the national recommendation and thus sediment should not be removed or should be stored with hazardous material. Based on the present status of the lake and paleolimnological results, two solutions are proposed: to further decrease the nutrients coming in the lake (possibly using filtrating plants) followed by flushing to increase lake water circulation. Physical capping of the sediment to avoid exchange of heavy metals and phosphorus release at the water/sediment interface could also be envisaged once the two prime solutions are in place.Peer reviewedPeer Reviewe
La deglaciación del valle del Ésera desde la Máxima Extensión del Hielo en los Pirineos
No full text[EN]
The Ésera valley is a narrow U-shape valley located in the Central Pyrenees. It has been modelled by the glacial activity during the Last Glacial Cycle. The combination of several methods as cosmogenic
exposure dating of glacial deposits and lacustrine core analyses in the Pllan d’Están proglacial lake has allowed to understand the complex dynamics of the Ésera glacier since the local glacial maximum extension (75 ka ago). After this maximum extension, the glacier retreated according with a warm interval within the Marine Isotope Stage (MIS) 3. A new glacial advance, likely corresponding with the Oldest Dryas (16 ka) was established from cosmogenic dates and subglacial sedimentation in the Pllan d’Están paleolake. From that time to nowadays, the Ésera glacier has retreated very quickly, especially during the Allerød period (13.8 ka). During the Little Ice Age,the Ésera glacier, divided in several smaller glaciers, left the thickest moraines conserved in this valley.[ES]
El valle del Ésera es un valle glaciar situado en los Pirineos Centrales, que fue modelado por la actividad glaciar durante el Último Ciclo Glaciar. La combinación de varios métodos como la datación por isótopos cosmogénicos de depósitos glaciares y el análisis de sondeos lacustres en el lago proglaciar de Pllan d’Están ha permitido
comprender la compleja dinámica con varios avances y retrocesos del glaciar Ésera desde su última máxima extensión (75 ka). Tras este máximo, el glaciar retrocedió coincidiendo con un intervalo cálido durante el MIS (Estadio Isotópico Marino) 3. Un nuevo avance glaciar fue datado hace 16 ka por isótopos cosmogénicos, llevando al lago de Pllan d’Están a un ambiente subglaciar. Desde entonces hasta la actualidad el glaciar del Ésera retrocedió muy rápidamente, especialmente durante el periodo Allerød (13.8 ka). Durante la Pequeña Edad de Hielo ocurrió el último avance del glaciar del valle del Ésera. Este periodo se reconoce por presentar la morrenas más elevadas y mejor conservadas del valle.This study was supported by the Spanish Autonomous Organism of National Parks project 2552/2020
(ORCHESTRA), the Spanish project PID2019-106050RB-I00 (PYCACHU), the Interreg-POCTEFA project OPCC ADAPYR and the Spanish project Diputación Provincial de Huesca Felix de Azara 2021. Ixeia Vidaller is supported by the grant FPU18/04978 and is enrolled in the PhD programme at the University of Zaragoza.Peer reviewe
Chrysophyte cyst relationships to water chemistry in Pyrenean lakes (NE Spain) and their potential for environmental reconstruction.
No full text14 páginas, 5 tablas, 7 figuras.Chrysophyte cysts were identified from the surface sediment of 105 mountain lakes in the Pyrenees (NE Spain),
and their statistical relationship to water chemistry was examined using canonical correspondence analysis (CCA).
The chemical parameters that explained significant and independent amounts of variability were alkalinity, pH,
potassium, nitrate and magnesium. In a CCA using these parameters, the first canonical axis was related to a
gradient of alkalinity and pH, which reflected the varying nature of the watershed bedrock in the Pyrenees, while
the second axis was correlated with potassium (negatively) and nitrate (positively). The potential for environmental
reconstructions of the five chemical parameters was further studied by: (i) analyzing the distribution of optima
and tolerances calculated by weighted-averaging (WA); (ii) carrying out detrended canonical correspondence
analysis (DCCA) with a single environmental variable; and (iii) examining the performance of WA-PLS transfer
functions. Acceptable transfer functions were obtained for alkalinity, pH and nitrate. However, for potassium and
magnesium the tolerance of cysts was too broad and the distribution of optima too skewed, respectively. The
possibility of reconstructing nitrogen-related issues using chrysophyte cysts is particularly interesting because of
the lack of direct chemical records of nitrogen compounds in sediments. Nitrate reconstructions using transfer
functions may be complemented by a holistic reconstruction using partial CCA, where, after subtracting the effects
of other chemicals, samples are ordered on a plain defined by potassium and nitrate. This ordination could show
down-core trends in lake productivity and renewal time.This study was supported by the CICYT of the Spanish Government (contract AMB93-0814-CO2-01), the European Commission (contract ENV4-CT97-0642, CHILL-10,000 project), the Comissionat per a Universitats i Recerca of the Catalan Government (grant 1999SGR00029) and a Ph. D. fellowship to SP from the Spanish Government.Peer reviewe
NAO proxy-based reconstruction from Iberian Peninsula (-150 to 2010 CE)
No full textWe present a quantitative NAO reconstruction for the central Iberian Peninsula (IP) over the last two millennia, along with its uncertainties, by applying a Bayesian approach
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