2,002 research outputs found
Deciphering chrysophyte responses to climate seasonality
No full text12 páginas, 5 figuras.Climate change involves alterations in
seasonality as well as shifts in mean annual temperature.
Cold temperate lakes show strong seasonality,
with winter ice cover and alternating mixing and
stratification periods during the ice-free season. These
physical changes are ultimately related to seasonal
weather variation and also drive annual phytoplankton
succession. Therefore, phytoplankton remains in lake
sediment records are potentially useful for reconstructing
past seasonal climate signals. With the
exception of investigations on varved sediments,
however, little research has been carried out on the
subject. Here we present two lines of evidence
demonstrating that chrysophyte stomatocysts can be
useful for inferring past climatic seasonality. First, we
show that marked seasonal stomatocyst replacement is
related to periods of the main physical processes in the
lake. Second, using instrumental climate data and
microfossils in sediment cores, we show that two main
components of stomatocyst variability over the last
*150 years are related to seasonal fluctuations. The
first of these components is related to stomatocysts
present during summer stratification that respond to
general warming trends, particularly in July and
August. The second component relates to stomatocysts
typically present in the spring and autumn mixing
periods. Numbers of these two stomatocyst types vary
inversely in response to variation in spring (April–
May) temperatures. The number of stomatocyst types
affected by spring temperatures is much greater than
those related to summer temperatures. We provide
evidence that chrysophyte stomatocysts are an excellent
proxy for spring air temperature reconstructions,
with little influence from summer or general annual
trends. We also show that with relatively little effort, it
is possible to categorise the chrysophyte stomatocyst
assemblage of a lake to carry out detailed investigation
of the record of seasonal changes preserved within the
sediment.This research was supported by a Marie
Curie Fellowship (CREATE) as part of the European
Community Program under contract number EVK2-CT-2000-
50007 and an I3P grant (2007–2010) to Sergi Pla from the
Spanish government. This study was funded by Spanish
Government research projects: GRACCIE (CSD2007-00067)
and ECOFOS (CGL2007-64177/BOS).Peer reviewe
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
Estructura poblacional i ecologia tròfica del seitó "Engraulis encrasicolus", de la Mediterrània nord-occidental
No full textMemoria de tesis doctoral presentada por Sergi Tudela Casanovas para obtener el título de Doctor por la Universitat de Girona (UdG), realizada bajo la dirección de la Dra. Isabel Palomera Laforga del Institut de Ciències del Mar (ICM-CSIC) y el Dr. Carles Pla de la Universitat de Girona (UdG)Tot i el ganpes del seitó, Engraulis encrasicolus (L. 1758), en el context de les pesqueries de la Mediterrània nord-occidental, alguns aspectes bàsics de la seva biologia han homàs pràcticament desconeguts fins el present. Entre ells, destaquen per la seva importància cabdal pel coneixement de l'espècie, l'estructura poblacional en l'àrea descrita i l'ecologia tròfica durant el període reproductor. [...]Peer Reviewe
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
Els Protagonistes de Quim Monzó i Sergi Pàmies: una aproximació a l'antiheroi postmodern
No full textAquest treball pretén estudiar els protagonistes de dos autors catalans contemporanis, Quim Monzó i Sergi Pàmies.
Seguint el mètode de la dialèctica hegeliana, es planteja dos conceptes inicials per argumentar-los i fer un intercanvi d’idees. A la part final es busca obtenir una síntesi significativa respecte dels antiherois analitzats de les obres La magnitud de la tragèdia, de Quim Monzó, i Sentimental, de Sergi Pàmie
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
Reduced precipitation can induce ecosystem regime shifts in lakes by increasing internal nutrient recycling
No full text© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Eutrophication is a main threat to continental aquatic ecosystems. Prevention and amelioration actions have been taken under the assumption of a stable climate, which needs reconsideration. Here, we show that reduced precipitation can bring a lake ecosystem to a more productive regime even with a decline in nutrient external load. By analyzing time series of several decades in the largest lake of the Iberian Peninsula, we found autocorrelated changes in the variance of state variables (i.e., chlorophyll and oxygen) indicative of a transient situation towards a new ecosystem regime. Indeed, exceptional planktonic diatom blooms have occurred during the last few years, and the sediment record shows a shift in phytoplankton composition and an increase in nutrient retention. Reduced precipitation almost doubled the water residence time in the lake, enhancing the relevance of internal processes. This study demonstrates that ecological quality targets for aquatic ecosystems must be tailored to the changing climatic conditions for appropriate stewardship.Project "Control limnológico bianual intensivo del lago de Sanabria," funded by the Confederación Hidrográfica del Duero (Ministry for the Ecological Transition and the Demographic Challenge), commissioned to the Centre for Hydrographic Studies (CEDEX), CIEMAT and other research institutions (Ref. 452-A-640.01.01/2014), to study the ecological functioning of Lake Sanabria and its basin (2015–2019).Peer reviewe
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