Los trabajos de este apartado están ordenados en estos contenidos temáticos:
[lmt-post-modified-info]
A/ CAMBIO CLIMÁTICO Y SUCESIÓN EN LAGOS
• 2002/ Ignacio Granados; Manuel Toro
Recent warming in a high mountain lake (Laguna Cimera, Central Spain) inferred by means of fossil chironomids
Lake Cimera (Lat. 40°15’50» N; Long. 05°18’15» W, Zmax = 9.4m, A = 4.5 ha, 2140 m a.s.l,) is one of the most remote and unpolluted high mountain lakes on the Sierra de Gredos (Central Spain). Intrannual and interannual variability in maximum water temperature and winter oxygen depletion can be related to climate variability (mainly air temperature), through controlling ice cover length. The extent of the oxygen depletion during ice cover period, which is related to this ice cover length, is a key factor controlling the relative abundance of chironomid (Diptera: Insecta) taxa, especially the low oxygen content adapted Chironomus sp. In this way, we have found a high negative correlation between the relative abundance of Chironomus head capsules in the sediment and the reconstructed air temperature in the last 200 years (n = 20, r = -0.75, p <0.001). The interpretation of such relationship throughout the fossil chironomid assemblage points to a recent warming (since ca mid 1980s) in Lake Cimera. The ecological interpretation of other taxa also supports this view. When applying to fossil chironomids of Lake Cimera the transfer functions developed to reconstruct summer past temperatures in the Alps, it is also well correlated with reconstructed air temperatures (n = 20, r = 0.45, p <0.01), especially when only the most accurate dating levels (top of the core, ca 75 years) are taken into account (n = 13, r = 0.75, p <0.01). However, 1) the linear regressions of both models show significantly different slopes, and 2) chironomid reconstruction underestimates in ca. 3 ºC air reconstruction. The later is probably because the fossil chironomid model has been developed for a different geographical region. Nevertheless, both models provide an independent line of evidence of a recent warming (since ca mid 1980s) in Lake Cimera. Our data also supports the use of chironomids head capsules as an effective tool to infer past temperatures.
El texto completo de este trabajo en Clic ¡
• 2002/ J. Catalan, M. Ventura, A. Brancelj, I. Granados, H. Thies, U. Nickus, A. Korhola, A. F. Lotter, A. Barbieri, E. Stuchlík, L. Lien, P. Bitušík, T. Buchaca, L. Camarero, G.H. Goudsmit, J. Kopáek, G. Lemcke, D.M. Livingstone, B. Müller, M. Rautio, M. Šiško, S. Sorvari, F. Šporka, O. Strunecký; M. Toro
Seasonal ecosystem variability in remote mountain lakes: implications for detecting climatic signals in sediment records
Weather variation and climate fluctuations are the main sources of ecosystem variability in remote mountain lakes. Here we describe the main patterns of seasonal variability in the ecosystems of nine lakes in Europe, and discuss the implications for recording climatic features in their sediments. Despite the diversity in latitude and size, the lakes showed a number of common features. They were ice-covered between 5–9 months, and all but one were dimictic. This particular lake was long and shallow, and wind action episodically mixed the water column throughout the ice-free period. All lakes showed characteristic oxygen depletion during the ice-covered-period, which was greater in the most productive lakes. Two types of lakes were distinguished according to the number of production peaks during the ice-free season. Lakes with longer summer stratification tended to have two productive periods: one at the onset of stratification, and the other during the autumn overturn. Lakes with shorter stratification had a single peak during the ice-free period. All lakes presented deep chlorophyll maxima during summer stratification, and subsurface chlorophyll maxima beneath the ice. Phosphorus limitation was common to all lakes, since nitrogen compounds were significantly more abundant than the requirements for the primary production observed. The major chemical components present in the lakes showed a short but extreme dilution during thawing. Certain lake features may favour the recording of particular climatic fluctuations, for instance: lakes with two distinct productive periods, climatic fluctuations in spring or autumn (e.g., through chrysophycean cysts); lakes with higher oxygen consumption, climatic factors affecting the duration of the ice-cover (e.g., through low-oxygen tolerant chironomids); lakes with higher water retention time; changes in atmospheric deposition (e.g., through carbon or pigment burial); lakes with longer stratification, air temperature changes during summer and autumn (e.g., through all epilimnetic species).
El texto completo de este trabajo en Clic ¡
• 2002/ Manel Leira; Luisa Santos
An early Holocene short climatic event in the northwest Iberian Peninsula inferred from pollen and diatoms
Pollen and diatom analyses have been carried out in a 490-cm long core collected from Laguna Lucenza (1420m a.s.l.; northwest Iberian Peninsula), spanning the last 10,000 yr. Pollen analyses show a decrease in deciduous Quercus pollen percentages and total pollen concentration after radiocarbon date 8350780 yr BP. The estimated age by linear interpolation for the peak of this event is about 9200 cal yr BP. Diatom analyses have been carried out using the same samples in order to obtain complementary information about past environmental conditions within the water body. Pollen and diatom records show a response to changes in the palaeoenvironmental conditions. Diatom concentrations are relatively low, indicating low productivity within the lake. Fragilaria species are dominant and Fragilaria exigua is notably more abundant than during previous periods. These changes in the diatom community reflect a decrease in lake pH. This would be consistent with longer periods of ice cover and cold conditions in the lake at this time. We interpret this episode as a response to climatic change probably due to climatic deterioration. This interval coincides, at least in part, with an episode of abrupt and short widespread climate change lasting from 9000 to 8000 yr BP.
El texto completo de este trabajo en Click ¡
• 2006/ Manuel Toro; Ignacio Granados; Santiago Robles; Carlos Montes
High mountain lakes of the Central Range (Iberian Peninsula): Regional limnology & environmental changes
High mountain lake ecosystems in the Iberian Peninsula, being more than 1700 water bodies, are represented mainly by small or medium size lakes (75 % with a surface less than 0.5 Ha.). The knowledge of their regional limnology in Spain is yet uneven and insufficient, as well as their ecological status and sensitivity to human activity impacts. This work describes the major limnological characteristics and functioning of high mountain lakes in the Spanish Central Range, and their relationships with regional environmental variables and existing human pressures. Some hydrological processes (turnover rate), thermal properties (ice-cover dynamics) or hydrochemical parameters (conductivity) are discussed in more detail in those lakes with long term monitoring data. The composition of planktonic and benthic communities responds to both human pressures and biogeographical or environmental aspects. The effects produced by tourism, cattle, lake damming, wastewater inflow, watershed erosion, introduction of the brook trout, or environmental warming, are studied in some lakes. Implemented management and restoration measures to reduce environmental impacts are described and evaluated.
El texto completo de este trabajo en Clic ¡
• 2010/ Sven Björk
Chapter 2 The Evolution of Lakes and Wetlands
When dealing with lake restoration, we should bear in mind that inland water ecosystems are not static units but subject to continuous evolution. Palaeolimnological studies have helped us to understand the development of lakes and their catchments. In particular, the development of northern European lakes has been studied very thoroughly. It has been revealed that the initially high productivity of lakes (shown by sediment growth rate) was due to the leaching of nutrients from the nutrient-rich moraine after the last deglaciation. With time, however, lake productivity dropped as the supply of nutrients from the catchment area diminished. This reduction depended partly on the decreased leaching and partly on the development of terrestrial vegetation as it accumulated and recycled nutrients. In southern Sweden, the current sediment growth rate is about 0.2 mm per year in more-orless- intact, shallow oligotrophic lakes, and about 0.5–1.0 mm per year in shallow eutrophic lakes. If a lake becomes polluted by the discharge of nutrient-rich sewage, the sediment growth rate can increase to about 10 mm per year. The ageing of lakes, and their potential terrestrialisation, depends on the balance between production and decomposition of organic matter. In northern latitudes, the break-down of organic matter in cold and oxygen-free sediment and peat is much slower than in warmer waters in the south where mineralisation processes take place at higher rates and over a longer period of the year. It is therefore much harder to prevent lakes in the north from being terrestrialised. M. Eiseltová (ed.), Restoration of Lakes, Streams, Floodplains, and Bogs in Europe: Principles and Case Studies, Wetlands: Ecology, Conservation and Management 3, DOI 10.1007/978-90-481-9265-6_2, © Springer Science+Business Media B.V. 2010
El texto completo de este trabajo en Clic ¡
• 2011/ C. L. Faithfull; A. Wenzel, T. Vrede; A.K. Bergström
Testing the light : nutrient hypothesis in an oligotrophic boreal lake
Anthropogenic changes in the nitrogen (N), phosphorus (P), and carbon (C) cycles have altered nutrient concentrations and the light climate in freshwaters globally. These factors affect phytoplankton (PPr) and bacterial production (BP), which constitute the basal energy resource for higher trophic levels in the pelagic zone of lakes. The light : nutrient hypothesis (LNH) predicts that although basal production decreases at low light, seston C: nutrient ratios also decrease, thus increasing food quality for crustacean zooplankton and potentially offsetting the negative effects of reduced food availability. We tested the LNH in an oligotrophic boreal lake by manipulating N, P, C and reducing light, and measuring PPr, BP, seston C: nutrient ratios and zooplankton biomass in 32 mesocosms. Low light strongly reduced zooplankton biomass in contrast to LNH predictions. PPr did not decrease with low light as predicted by the LNH, however, the phytoplankton community shifted towards low light adapted, but potentially less edible phytoplankton species, such as colony forming Dinobryon (Chrysophyta) and gymnoid (Dinoflagellata) taxa, which were negatively correlated with zooplankton biomass. Seston C: nutrient ratios did not decrease with reduced light, possibly due to the high abundance of mixotrophic phytoplankton across treatments. BP decreased with low light and correlations between BP, bacterial biomass, ciliates and zooplankton suggest that bacteria may be coupled with zooplankton biomass. Thus, the LNH was inadequate when predicting changes in crustacean zooplankton biomass in this typical oligotrophic boreal system, where Daphnia is rare and mixotrophic phytoplankton are abundant. Instead, alternative explanations, such as changes in phytoplankton edibility and energy transferred through the microbial food chain may need investigation to explain reduced zooplankton biomass in low light treatments.
El texto completo de este trabajo en Clic ¡
• 2011/ Lourdes López-Merino; Ana Moreno; Manel Leira, Javier Sigró; Penélope González-Sampériz; Blas L. Valero-Garcés; José Antonio López-Sáenz; Manola Brunet; Enric Aguilar
Two hundred years of environmental change in Picos de Europa National Park inferred from sediments of Lago Enol, northern Iberia
We present a study of two short sediment cores recovered from Lago Enol, in the Picos de Europa National Park, Cantabrian Mountains, northern Iberia. We inferred past climate conditions and anthropogenic impacts using geochemical and biological (pollen and diatoms) variables in the dated sequences, in conjunction with temperature and precipitation data collected since 1871 at meteorological stations in the region. The record provides evidence of environmental changes during the last 200 years. At the end of the Little Ice Age (*1800–1875 AD) the region was characterized by an open landscape. Longterm use of the area for mixed livestock grazing in the mountains, and cultivation of rye during the nineteenth century, contributed to the expansion of grassland at the expense of forest. Warmer temperatures since the end of the nineteenth century are inferred from a change in diatom assemblages and development of the local forest. Socioeconomic transformation during the twentieth century, such as livestock changes related to dairy specialization, planting of non-native trees, mining activities, and management of the national park since its creation in 1918, caused profound changes in the catchment and in the lake ecology. The last several decades (*1970–2007 AD) of the Lago Enol sediment record are strikingly different from previous periods, indicating lower runoff and increasing lake productivity, particularly since AD 2000. Today, the large number of tourists who visit the area cause substantial impacts on this ecosystem.
El texto completo de este trabajo en Clic ¡
• 2012/ Brian Moss
Cogs in the endless machine: Lakes, climate change and nutrient cycles: A review
Lakes have, rather grandly, been described as sentinels, integrators and regulators of climate change (Williamson et al., Limnol. Oceanogr. 2009; 54: 2273–82). Lakes are also part of the continuum of the water cycle, cogs in a machine that processes water and elements dissolved and suspended in myriad forms. Assessing the changes in the functioning of the cogs and the machine with respect to these substances as climate changes is clearly important, but difficult. Many other human-induced influences, not least eutrophication, that impact on catchment areas and consequently on lakes, have generally complicated the recording of recent change in sediment records and modern sets of data. The least confounded evidence comes from remote lakes in mountain and polar regions and suggests effects of warming that include mobilisation of ions and increased amounts of phosphorus.
A cottage industry has arisen in deduction and prediction of the future effects of climate change on lakes, but the results are very general and precision is marred not only by confounding influences but by the complexity of the lake system and the infinite variety of possible future scenarios. A common conclusion, however, is that warming will increase the intensity of symptoms of eutrophication. Direct experimentation, though expensive and still unusual and confined to shallow lake and wetland systems is perhaps the most reliable approach. Results suggest increased symptoms of eutrophication, and changes in ecosystem structure, but in some respects are different from those deduced from comparisons along latitudinal gradients or by inference from knowledge of lake behaviour. Experiments have shown marked increases in community respiration compared with gross photosynthesis in mesocosm systems and it may be that the most significant churnings of these cogs in the earth–air–water machine will be in their influence on the carbon cycle, with possibly large positive feedback effects on warming.
El texto completo de este trabajo en Clic ¡
• 2015 / G. Sánchez-López, A. Hernández, S. Pla-Rabes, M. Toro, I. Granados, J. Sigró, R. M. Trigo, M. J. Rubio-Inglés, L. Camarero, B. Valero-Garcés; S. Giralt
Cogs in the endless machine: Lakes, climate change and nutrient cycles: A review
Three Spanish alpine lakes located in the Central Range (Peñalara Lake and Cimera Lake) and the Pyrenees (Redon Lake) are selected to understand the effects of the North Atlantic Oscillation (NAO) on ice phenology. A conceptual lake model is formulated based on Pearson’s correlation coefficients obtained between season-scale time series of the NAO index, climatic data (i.e., precipitation, air temperature and snow data) and limnological variables (ice phenology records). The results suggest that the effects of the NAO are only reflected in the thawing process via the air temperature and the insulating effect of snow accumulation on the ice cover. An altitude component is evident in our survey because the effects of the NAO on Peñalara Lake (the lowest altitude studied lake) are restricted to winter, whereas for Redon Lake (the highest altitude studied lake), the effects extend into spring. A latitudinal component is also clear when comparing our data with northern European lakes. Snow accumulation primarily depends on the air temperature at high latitudes, and both precipitation and the air temperature control snow accumulation at lower latitudes. Consequently, in northern Europe, the NAO signal is primarily reflected in lake ice phenology via the air temperature, whereas our results confirm that in southern Europe, the strong dependence of precipitation on the NAO determines the importance of the NAO for lake ice cover.
El texto completo de este trabajo en Clic ¡
• 2018/ Rieradevall M., González-Sampériz P., Pérez-Martínez C., Tarrats P., Leunda M., Aranbarri J., Gil-Romera G., Prata N.
Evaluación y seguimiento del cambio global en dos lagos de alta montaña (Enol y Marboré) de la Red Española de Parques Naturales: indicadores biológicos (CLAM2)
En el proyecto CLAM2 se han estudiado las comunidades biológicas actuales y subfósiles de los lagos de Enol y Marboré, así como las secuencias palinológicas y lluvia polínica de ambos sistemas para poder obtener indicadores fiables de cambio global en escalas temporales largas. Los resultados muestran que el lago Enol tiene unos valores de densidad y biomasa de fitoplancton mucho mayores que Marboré, siendo el primero oligo-mesotrófico y el segundo ultraoligotrófico. En el epiliton de la zona litoral domina Encyonema minutum en Marboré y Encyonopsis minuta en Enol. Marboré tiene un zooplancton con una riqueza específica menor que Enol, con Diaptomus cyaneus como especie dominante en el primero y Ceriodaphnia quadrangula en el segundo. En lo referente al bentos profundo, dominan los quironómidos con especies típicas de lagos oligotróficos de montaña: en Marboré Micropsectra radialis y Pseudodiamesa nivosa, mientras que en Enol la única especie presente en el fondo es Chironomus plumosus, lo que indica falta de oxígeno en la parte profunda del lago. En las zonas más someras de Enol, la comunidad es diferente y cuando existen praderas de caráceas domina Paratanytarsus bituberculatus. Por lo que respecta a la lluvia polínica, tanto en Marboré como en Enol, Pinus aparece sobre-representado frente a las especies más próximas al lago, mientras que Fagus sí se registra en proporción a su abundancia relativa. A pesar de la abundante presencia de zonas abiertas y prados en la actualidad, estas formaciones están claramente infra-representadas en el contenido polínico. Los datos paleolimnológicos muestran que Chironomus se hace más abundante en la parte superior del sondeo en Enol, lo que indicaría una eutrofización reciente del mismo, mientras que Marboré presenta las mismas especies que se encuentran en la fauna actual. Las secuencias palinológicas fósiles también muestran cambios a lo largo del tiempo, registrando una antropización intensa en fechas recientes. Mientras Marboré resulta un lago interesante para usarlo como referencia de posibles cambios globales en el futuro, Enol ya muestra signos importantes de este cambio.
El texto completo de este trabajo en Clic ¡
• 2020 / García-Alix, A., Toney, J. L., Jiménez-Moreno, G., Pérez-Martínez, C., Jiménez, L., Rodrigo-Gámiz, M., Anderson, R. S., Camuera, J., Jiménez-Espejo, F. J., Peña-Angulo, D., and Ramos-Román, M. J.
Algal lipids reveal unprecedented warming rates in alpine areas of SW Europe during the industrial period
Alpine ecosystems of the southern Iberian Peninsula are among the most vulnerable and the first to respond to modern climate change in southwestern Europe. While major environmental shifts have occurred over the last ∼1500 years in these alpine ecosystems, only changes in the recent centuries have led to abrupt environmental responses, but factors imposing the strongest stress have been unclear until now. To understand these environmental responses, this study, for the first time, has calibrated an algal lipid-derived temperature proxy (based on long-chain alkyl diols) to instrumental historical data extending alpine temperature reconstructions to 1500 years before present. These novel results highlight the enhanced effect of greenhouse gases on alpine temperatures during the last ∼200 years and the long-term modulating role of solar forcing. This study also shows that the warming rate during the 20th century (∼0.18 ∘C per decade) was double that of the last stages of the Little Ice Age (∼0.09 ∘C per decade), even exceeding temperature trends of the high-altitude Alps during the 20th century. As a consequence, temperature exceeded the preindustrial record in the 1950s, and it has been one of the major forcing processes of the recent enhanced change in these alpine ecosystems from southern Iberia since then. Nevertheless, other factors reducing the snow and ice albedo (e.g., atmospheric deposition) may have influenced local glacier loss, since almost steady climate conditions predominated from the middle 19th century to the first decades of the 20th century.
El texto completo de este trabajo en Clic ¡
B/ ESTADO TRÓFICO DE LOS LAGOS
• 1982/ OCDE
Eutrophication of waters monitoring. Assessment and control.
Idiosyncrasies, erroneous assumptions and gaps are still hampering lake evaluations, despite several decades of defining the trophic state of lakes. I reevaluated nutrient and algal biomass limits that group lakes into oligo-, meso-, eu- and hyper eutrophic lakes at transition concentrations of 10, 30 and 100 μg · L−1 average total phosphorus concentration of the summer epilimnion. I investigated the direct and indirect effects of general lake characteristics like morphometry and geochemistry (water hardness and color) on lake trophic state and formulated models to deal with their significant influences. Nutrient and biomass concentrations as well as quantitative measures of anoxia were used to determine the trophic state. I demonstrated that the number of coldwater fish species may be used to classify the lower trophic levels in geographically constraint areas. Limits and models were established with data from well-studied lakes and verified with literature data from worldwide lakes. Trophic state limits were set for oligo-, meso-, eu- and hypereutrophic lakes at transition concentrations for average total nitrogen of 350, 650 and 1,200 μg·L−1, for summer chlorophyll of 3.5, 9 and 25 μg·L−1, for summer transparency (Secchi disk depth) of 4, 2 and 1 m, for die anoxic factor of 20, 40 and 60 d·summer−1, and for the areal oxygen depletion rate of 250, 400 and 550 mg·m−2·d−1.
El texto completo de este trabajo en Clic ¡
• 1996/ Gertud K. Nürnberg
Trophic state of clear and colored, soft-and hardwater lakes with special consideration of nutrients, anoxia, phytoplankton and fish
Idiosyncrasies, erroneous assumptions and gaps are still hampering lake evaluations, despite several decades of defining the trophic state of lakes. I reevaluated nutrient and algal biomass limits that group lakes into oligo-, meso-, eu- and hyper eutrophic lakes at transition concentrations of 10, 30 and 100 μg · L−1 average total phosphorus concentration of the summer epilimnion. I investigated the direct and indirect effects of general lake characteristics like morphometry and geochemistry (water hardness and color) on lake trophic state and formulated models to deal with their significant influences. Nutrient and biomass concentrations as well as quantitative measures of anoxia were used to determine the trophic state. I demonstrated that the number of coldwater fish species may be used to classify the lower trophic levels in geographically constraint areas. Limits and models were established with data from well-studied lakes and verified with literature data from worldwide lakes. Trophic state limits were set for oligo-, meso-, eu- and hypereutrophic lakes at transition concentrations for average total nitrogen of 350, 650 and 1,200 μg·L−1, for summer chlorophyll of 3.5, 9 and 25 μg·L−1, for summer transparency (Secchi disk depth) of 4, 2 and 1 m, for die anoxic factor of 20, 40 and 60 d·summer−1, and for the areal oxygen depletion rate of 250, 400 and 550 mg·m−2·d−1.
El texto completo de este trabajo en Clic ¡
• 1997/ Howard P. Gross, Wayne A. Wurtsbaugh, Chris Luecke y Phaedra Budy
Fertilization of an oligotrophic lake with a deep chlorophyll maximum: predicting the effect on primary productivity
We investigated how epilimnetic fertilization would affect chlorophyll levels and light penetration of oligotrophic sockeye salmon (Oncorhynchus nerka) lakes and how the resulting self-shading would affect primary production of the prominent deep chlorophyll maxima (DCM) of the lakes. Epilimnetic nutrient additions to large mesocosms (330 m3) in Redfish Lake, Idaho, increased levels of primary productivity and chlorophyll a but decreased Secchi depths and light available in the metalimnion and hypolimnion. Redfish Lake and other Sawtooth Valley (Idaho) lakes had DCM in which the mean chlorophyll a peaks were 240–-1000% of mean epilimnetic chlorophyll a concentrations. The DCM existed at low light levels and accounted for 36-–72% of the lakes’ primary production. Simulations using photosynthesis–irradiance (P–I) curves demonstrated that fertilization would increase predicted water column primary production by 75–-101%. Most of this increase occurred in the epilimnion, with only a slight decrease occurring in the DCM as the result of increased shading.
El texto completo de este trabajo en Clic ¡
• 2006/ Manel Leira, Phil Jordan, David Taylor, Catherine Dalton, Helen Bennion, Neil Rose y Kenneth Irvine
Assessing the ecological status of candidate reference lakes in Ireland using palaeolimnology
1. The European Union (EU) Water Framework Directive (WFD) requires that member states establish type-specific reference conditions for all waterbodies, including freshwater lakes. This presents a problem in those locations where human activity has resulted in significant changes to the biological, chemical and physical characteristics of waterbodies. 2. Seventy-six oligotrophic and meso-oligotrophic [0–19 μ g total phosphorus (TP) L − 1 ] lakes thought to be relatively unimpacted by human activity have been nominated as candidate reference lakes (CRL) by the Irish Environmental Protection Agency. This research has used palaeolimnological (lake sediment-based) techniques to test the actual and historical ecological site-specific status of a representative selection of these CRL. Where the temporal record of sedimentation was sufficiently long, the study adopted c. 1850 as the primary baseline date for reference conditions. 3. Short sediment cores were obtained from the deepest parts of 35 CRL, and chronologies were established from profiles of spheroidal carbonaceous particles (SCP). Twenty-two cores of sediment appeared to date back to c. 1850 on the basis of SCP concentrations. Unless the SCP chronologies suggested otherwise, diatom assemblages present in top and bottom samples from the cores were used as proxies of, respectively, present-day and reference conditions. Past lake water pH (DI-pH) and TP concentration (DI-TP) were inferred from the diatom data. Higher resolution sampling (up to five sediment samples per core) was adopted at seven sites where the SCP-based chronology was more robust and for at least one core from each of the most common types of CRL. Sediment chemistry data were determined to identify possible anthropogenic drivers of the observed changes in the diatom assemblages. 4. Ordination and dissimilarity measures identified the main patterns of variation in the diatom data. Eleven of 34 CRL for which diatom data were available showed little or no change in biological status between core top and bottom samples. Core bottom samples in six of these dated back to pre- or c. 1850 and reference (and high ecological) status could therefore be confirmed in these cases. The estimated age of core bottom samples in the remaining five cores was in the period just after c . 1850 to c. 1950 (four cores) or was impossible to determine (one core). Twenty-three (68%) of the CRL sampled showed biologically important deviation from the reference condition, with acidification and nutrient enrichment seemingly the main causes of change. Catchment disturbance, notably peat erosion possibly linked to recent afforestation, also appeared to have been a factor in some cases. 5. Synthesis and applications. This study provides the first systematic examination of changes to water quality in (perceived) pristine lakes over the last c . 150 years for Ireland, and demonstrates the potential of palaeolimnology to support the implementation of the WFD. The results indicate that diatom communities in low alkalinity lakes have been particularly altered, and acidification and nutrient enrichment appear to have been important drivers for some lakes. Furthermore, higher resolution results call into question the validity of applying c. 1850 as the date for reference conditions across Ireland.
El texto completo de este trabajo en Clic ¡
• 2009/ Manel Leira; G. Chen; C. Dalton; K. Irvine; D. Taylor
Patterns in freshwater diatom taxonomic distinctness along an eutrophication gradient
Three sediment cores have been studied from the Morskie Oko (MOK), Przedni Staw Polski (PSP), and Czarny Staw Gąsienicowy (CSG) lakes to examine the recent environmental history of the alpine lakes located in the Polish part of the Tatra Mountains (Carpathians). Changes in the total phosphorus concentration in the water over the past centuries were reconstructed based on diatom data (DI-TP), assuming that diatoms are good indicators of productivity in lakes. The results of the analysis showed significant alterations in the trophic status of the studied lakes over the past 50 years. Clear changes from oligotrophy to mesotrophy occurred in the lakes located close to year-round mountain huts on the shores of MOK and PSP. In contrast, DI-TP decreased in CSG, and the only symptom of higher productivity in the lake was an increase in total organic carbon.
El texto completo de este trabajo en Clic ¡
• 2014/ Elwira Sienkiewicz y Michał Gąsiorowski
Changes in the Trophic Status of Three Mountain Lakes – Natural or Anthropogenic Process?
Three sediment cores have been studied from the Morskie Oko (MOK), Przedni Staw Polski (PSP), and Czarny Staw Gąsienicowy (CSG) lakes to examine the recent environmental history of the alpine lakes located in the Polish part of the Tatra Mountains (Carpathians). Changes in the total phosphorus concentration in the water over the past centuries were reconstructed based on diatom data (DI-TP), assuming that diatoms are good indicators of productivity in lakes. The results of the analysis showed significant alterations in the trophic status of the studied lakes over the past 50 years. Clear changes from oligotrophy to mesotrophy occurred in the lakes located close to year-round mountain huts on the shores of MOK and PSP. In contrast, DI-TP decreased in CSG, and the only symptom of higher productivity in the lake was an increase in total organic carbon.
El texto completo de este trabajo en Clic ¡
• 2016/ Carmen López Rodríguez; Manel Leira; Ramón Valle; Gabriel Moyá Niell
El fitoplancton como indicador de calidad de masas de agua muy modificadas en la DMA. El lago artificial de As Pontes (A Coruña. España)
Se recogen los primeros resultados del estudio de la composición y abundancia del fitoplancton del lago artificial de As Pontes, desde 2009 hasta 2014, destinados a la evaluación del potencial ecológico de las masas de aguas continentales en el marco de la implantación de la Directiva Marco Europea del Agua (DMA) en Galicia. Se han identificado un total de 125 taxa: 22 Cyanophyta, 47 Heterokontophyta de las cuales 42 son Bacillariophyceae, 4 Chrysophyceae y 1 Xantophyceae, 6 Dinophyta, 2 Cryptophyta, 4 Euglenophyta y 44 Chlorophyta. Ninguna de ellas se reconoce como tóxica, aunque se ha detectado una gran concentración de cistes que asociamos a la crisofícea Mallomonas sp. a finales de agosto de 2013. El estado trófico actual del lago se corresponde con una situación de oligotrofía, produciéndose una disminución de la biomasa del fitoplancton y de los factores de producción a medida que se avanzaba en los muestreos. A partir de la composición cualitativa y cuantitativa del fitoplancton y de las variables que definen su estado trófico, podemos concluir que el lago se encuentra en buenas condiciones ecológicas, de acuerdo a los criterios de la DMA.
El texto completo de este trabajo en Clic ¡
• 2016/ Eglantine Chappuis; Enric Ballesteros; Esperança Gracia
Temporary emersion enhances amphibious Isoetes production
La emersión temporal aumenta la producción de los Isoetes anfibios. En este trabajo se ha medido la producción primaria anual de dos isoetes anfibios en dos sistemas temporales diferentes en el NE de España: Isoetes echinospora, en una charca semipermanente de alta montaña y Isoetes delilei, en una charca temporal mediterránea. La producción primaria de las hojas mostró una distribución unimodal con un máximo en julio para I. echinospora y en abril para I. delilei. La población de I. echinospora produjo 38.7 g PS m–2y–1 (15.5 g C m–2y–1) en hojas el año de completa inmersión, pero la producción aumentó a 49.3 g PS m–2y–1 (19.7 g C m–2y–1) el año en el que las plantas estuvieron emergidas durante dos meses (incremento del 27.4%). La producción de hojas de I. delilei también aumentó significativamente después de la emersión (la charca se seca anualmente) y alcanzó una producción anual de 676.7 g PS m–2y–1 (265.3 g C m–2y–1). La producción primaria de hojas de I. delilei fue 15 veces mayor que la de I. echinospora y muy superior a los rangos descritos para los isoétidos sumergidos. El incremento de producción de I. echinospora en condiciones de emersión temporal junto con la inusual y elevada producción de I. delilei en una charca temporal, sugieren que la emersión temporal aumenta la producción primaria en los isoetes anfibios.
El texto completo de este trabajo en Clic ¡
• 2016/ Sandra Poikane , Martyn Kelly , Marco Cantonati
Benthic algal assessment of ecological status in European lakes and rivers: Challenges and opportunities
This opinion paper introduces a special series of articles dedicated to freshwater benthic algae and their use in assessment and monitoring. This special series was inspired by talks presented at the 9th International Congress on the Use of Algae for Monitoring Rivers and Comparable Habitats (Trento, Italy, 2015), the latest of a series of meetings started in 1991. In this paper, we will first provide a brief overview of phytobenthos methods in Europe. Then, we will turn towards the ‘dark side’ of phytobenthos and describe four particular problems for phytobenthos assessment in the European Union: (1) over-reliance on a single group of algae (mostly diatoms) to the exclusion of other groups; (2) relatively low adoption of benthic algae for ecological assessments in lakes; (3) absence of measures of phytobenthos abundance; (4) approaches used to define boundaries between ecological classes. Following this, we evaluate the strengths and limitations of current phytobenthos assessment methods against 12 criteria for method evaluation addressing four areas: ecological rationale, performance, feasibility of implementation, and use in communication and management. Using these criteria, we identify and discuss three general challenges for those developing new methods for phytobenthos-based assessment: a weak ecological rationale and insufficient consideration of the role of phytobenthos as a diagnostic tool and for communicating ecosystem health beyond a narrow group of specialists. The papers in the special series allow a comparison with the situation and approaches in the USA, present new methods for the assessment of ecological status and acidification, provide tools for an improved management of headwaters and petrifying springs, discuss the utility of phytobenthos for lake assessments, and test the utility of functional measures (such as biofilm phosphorus uptake capacity, PUC).
El texto completo de este trabajo en Clic ¡
• 2016/ Karpowicz M., Górniak A., Więcko A. & Cudowski A.
The variability of summer phytoplankton in different types of lakes in North East Poland (Suwałki Landscape Park)
This study describes summer phytoplankton communities in 27 lakes in the Suwałki Landscape Park (SLP) using in situ fluorescence methods. Low chlorophyll-a concentrations were noted in most of the studied lakes, particularly in the deepest lakes with highest surface area. Green algae, diatoms and cryptophyta were dominant components of lake phytoplankton. Higher chlorophyll-a concentrations in the shallow or more eutrophicated lakes were connected with an increase of cyanobacteria and cryptophyta concentrations as well as with a decrease in the share of diatoms in phytoplankton structure. Vertical distribution of phytoplankton in stratified lakes revealed the presence of deep chlorophyll layers just below the thermocline where the maximum concentrations of phytoplankton were up to 15 times higher than in the epilimnion zone. The deepest maximum concentration of phytoplankton was noted at a depth of 16.5 metres in Lake Jeglówek. In some lakes two or three significant increases of phytoplankton concentration in the vertical profile were observed, caused by intensive development of different algae groups.
El texto completo de este trabajo en Clic ¡
• 2017/ Karpowicz M. & Ejsmont-Karabin J.
Effect of metalimnetic gradient on phytoplankton and zooplankton (Rotifera, Crustacea) communities in different trophic conditions
Theory predicts and recent study revealed that depth of the thermocline can strongly influence the nutrient availability and composition of plankton communities. We are focused on the effect of metalimnetic gradients on water chemistry and plankton communities in three stratified lakes with different trophic conditions. Vertical changes in water chemistry revealed significant increase of macroelement concentrations in the metalimnion of all studied lakes. However, there was no significant increase of nutrient concentrations in the thermocline of lakes with smoother metalimnetic gradient, whereas sharp and deep thermocline zone caused higher concentration of orthophosphates and dissolved inorganic nitrogen in the metalimnion. The maximum concentrations of phytoplankton were observed just below the thermocline and were caused mostly by the abundance of diatoms and cryptophytes. Vertical distribution of the crustacean zooplankton was similar to the distribution of phytoplankton. Especially, Daphnia cucullata was strongly related with the phytoplankton distribution and reached maximum densities in deep layers with high chlorophyll concentrations, and, conversely, smaller crustacean species and rotifers were not affected by the vertical distribution of phytoplankton.
El texto completo de este trabajo en Clic ¡
• 2018/ Evanthia Mantzouki et al.
A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins
Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.
El texto completo de este trabajo en este link Clic ¡
• 2018/ Tomasz Lenard, W. Ejankowski & Małgorzata Poniewozik
Does an increase in water color intensity affect the lake trophic status and phytoplankton metrics?
During the 11-year period covered by this study (2003–2013), high precipitation events increased the water level in the deep hardwater of Lake Rogóźno (Eastern Poland), causing its water to become browner. We investigated the effect of a change in water color on the physical, chemical, and biological parameters of the lake. The concentration of total phosphorus and nitrogen decreased, whereas the total phytoplankton biomass, coupled with a high biomass of flagellate species, increased, with the increase in water color intensity. Such changes had an effect on the determination of ecological status, based on selected phytoplankton metrics (i.e., Polish, German, and Estonian) as well as the trophic status of Lake Rogóźno. The decrease of phosphorus concentration associated with an increase in water color intensity improved the trophic status of the lake based on Carlson’s Trophic State Index. The changes in the phytoplankton community caused the deterioration of the ecological status of the lake when using the Polish and German indices adopted for clear water lakes. The use of the Estonian index, which is adapted to colored lakes, suggested that, despite the increase in water color intensity, the good ecological status of the lake was maintained or even improved. Our findings suggest that, in the event of a transformation like the one that occurred in the lake studied here, the use of only one index, adapted by state environmental monitoring programs in individual European countries, may be insufficient for the appropriate assessment of the ecological status of European lakes.
El texto completo de este trabajo en este link Clic ¡
• 2019/ Morales-Baquero R., Pérez-Martínez C., Ramos-Rodríguez E., Sánchez-Castillo P., Villar-Argaiz M. & Conde-Porcuna J.M.
Zooplankton advective losses may affect chlorophyll-a concentrations in fishless high-mountain lakes
Hydraulic washout of lakes and reservoirs is recognized as a major regulating factor of both, phyto- and zooplankton populations. We have analysed the changes in the chlorophyll-a concentration in 21 high-mountain lakes from Sierra Nevada. Eleven lakes proved to have superficial diffuse inlets and outlets (open lakes) while the other 10 have no outlets, or no permanent outlets (closed lakes), where the plankton losses by washout are not possible. The lakes were sampled on two occasions during the ice-free season: just after the spring thaw (July) and by late August, after plankton development. In July, chlorophyll-a was quite similar between the closed and open lakes while in August the open lakes had about three-fold more chlorophyll-a than did closed ones. Model selection analysis made with 12 variables than can affect chlorophyll-a indicated that, in July, chlorophyll- a was related mainly to the maximum depth of closed lakes although the type of lake (closed or open) had no effect. However, in August, the type of lake (more chlorophyll-a in open than in closed lakes) and the ratio between dissolved inorganic nitrogen and total phosphorus (DIN:TP ratio) (higher values, lower chlorophyll-a), was related to chlorophyll-a concentration. The results of DIN, soluble reactive phosphorus (SRP) and nutrient ratios did not indicate a different nutrient availability between open and closed lakes in either of the two periods considered. Nevertheless, the data available showed that the zooplankton was, on average, about two-fold more abundant in the closed lakes than in the open ones during the entire ice-free season. These results indicate that the advective losses caused by the water flow could be greater for the zooplankton than for the phytoplankton, interfering with the coupling of trophic chains. Thus, part of primary production in the open lakes could not be transferred to higher trophic levels because of the zooplankton losses.
El texto completo de este trabajo en este link Clic ¡
C/ PRESIONES ANTRÓPICAS
• 2007/ Christian Bigler, Lucien von Gunten, André F. Lotter, Sonja Hausmann, Alex Blass, Christian Ohlendorf; Michael Sturm
Quantifying human-induced eutrophication in Swiss mountain lakes since AD 1800 using diatoms
Sedimentary diatom assemblages from three lakes in the southeastern Swiss Alps were analysed at high temporal resolution since AD 1800. Altered land-use patterns, increasing population and exploitation through tourism are clearly reflected in annually laminated sediments of Lej da San Murezzan (Lake St Moritz) and Lej da Silvaplauna (Lake Silvaplana). Diatom assemblages originally dominated by Cyclotella taxa are replaced by taxa indicating higher total phosphorus (TP) concentrations, such as Asterionella formosa, Fragilaria crotonensis and Stephanodiscus parvus. In Lej da la Tscheppa, located well above the treeline in a catchment that was hardly exposed to human impact, Cyclotella comensis prevails throughout the entire sediment sequence. Quantitative estimates of past TP concentrations were inferred using a newly developed regional diatom-TP inference model based on 119 modern samples. In Lej da la Tscheppa diatoms imply stable, low TP concentrations (~10 μg/l), which can be considered as natural background concentration. Elevated TP levels are inferred for Lej da San Murezzan (max. 60 μg/l) since AD 1910 and for Lej da Silvaplauna (max. 40 μg/l) since AD 1950, corroborated by changes in sedimentary biogenic silica concentration and organic carbon content. Since ~AD 1970 improved waste water management led to a considerable reduction in TP loading in Lej da Silvaplauna and Lej da San Murezzan.
El texto completo de este trabajo en Clic ¡
• 2005/ Richard W. Battarbee
Mountain lakes, pristine or polluted?
Este artículo presenta las conclusiones de varios proyectos de colaboración en el estudio de lagos de montaña remotos distribuidos por Europa y financiados por la Unión Europea. De forma particular describe como el registro sedimentario de varias localidades clave puede ser usado para identificar el cambio temporal, la intensidad y el impacto de la contaminación atmosférica en lagos por deposición ácida, metales traza y compuestos orgánicos trazadores. Este trabajo también describe el trabajo reciente para ayudar a valorar el impacto del cambio climático del siglo XX sobre estos lagos y si los cambios observados son el resultado de la variabilidad climática natural o el aumento del efecto invernadero.
El texto completo de este trabajo en Clic ¡
• 2018/ M.A. Burgos, D. Mateos, V.E. Cachorro, C. Toledano, A.M. de Frutos, A. Calle, A. Herguedas, J.L. Marcos
An analysis of high fine aerosol loading episodes in north-central Spain in the summer 2013 – Impact of Canadian biomass burning episode and local emissions
This work presents an evaluation of a surprising and unusual high turbidity summer period in 2013 recorded in the north-central Iberian Peninsula (IP). The study is made up of three main pollution episodes characterized by very high aerosol optical depth (AOD) values with the presence of fine aerosol particles: the strongest long-range transport Canadian Biomass Burning (BB) event recorded, one of the longest-lasting European Anthropogenic (A) episodes and an extremely strong regional BB. The Canadian BB episode was unusually strong with maximum values of AOD(440 nm)∼0.8, giving rise to the highest value recorded by photometer data in the IP with a clearly established Canadian origin. The anthropogenic pollution episode originated in Europe is mainly a consequence of the strong impact of Canadian BB events over north-central Europe. As regards the local episode, a forest fire in the nature reserve near the Duero River (north-central IP) impacted on the population over 200 km away from its source. These three episodes exhibited fingerprints in different aerosol columnar properties retrieved by sun-photometers of the AErosol RObotic NETwork (AERONET) as well as in particle mass surface concentrations, PMx, measured by the European Monitoring and Evaluation Programme (EMEP). Main statistics, time series and scatterplots relate aerosol loads (aerosol optical depth, AOD and particulate matter, PM) with aerosol size quantities (Ångström Exponent and PM ratio). More detailed microphysical/optical properties retrieved by AERONET inversion products are analysed in depth to describe these events: contribution of fine and coarse particles to AOD and its ratio (the fine mode fraction), volume particle size distribution, fine volume fraction, effective radius, sphericity fraction, single scattering albedo and absorption optical depth. Due to its relevance in climate studies, the aerosol radiative effect has been quantified for the top and bottom of the atmosphere, obtaining mean daily values for this extraordinary summer period of −14.5 and −47.5 Wm−2, respectively.
El texto completo de este trabajo en Clic ¡
• 2016/ M.B. da Silva, N. Abrantes, V. Nogueira, F. Gonçalves, R, Pereira
TiO2 nanoparticles for the remediation of eutrophic shallow freshwater systems: Efficiency and impacts on aquatic biota under a microcosm experiment
The application of nanomaterials (NMs) in the remediation of eutrophic waters, particularly in the control of internal loading of nutrients, has been started, but limited investigations evaluated the effectiveness of these new treatment approaches and of their potential impacts on species from shallow freshwater lakes. The present work investigated, under a microcosm experiment, the application of a TiO2 nanomaterial both for reducing nutrient (mainly phosphorus and nitrogen forms) desorption and release from sediments (preventive treatment-PT) and for eliminating algal blooms (remediation treatment-RT). Furthermore, we also intended to assess the potential impacts of nano-TiO2 application on key freshwater species. The results showed the effectiveness of nano-TiO2 in controlling the release of phosphates from surface sediment and the subsequent reduction of total phosphorus in the water column. A reduction in total nitrogen was also observed. Such changes in nutrient dynamics contributed to a progressive inhibition of development of algae after the application of the NM in PT microcosms. Concerning the ability of nano-TiO2 to interact with algal cells, this interaction has likely occurred, mainly in RT, enhancing the formation of aggregates and their rapid settlement, thus reducing the algal bloom. Both treatments caused deleterious effects on freshwater species. In PT, Daphnia magna and Lemna minor showed a significant inhibition of several endpoints. Conversely, no inhibitory effect on the growth of Chironomus riparius was recorded. In opposite, C. riparius was the most affected species in RT microcosms. Such difference was probably caused by the formation of larger TiO2-algae aggregates in RT, under a high algal density, that rapidly settled in the sediment, becoming less available for pelagic species. In summary, despite the effectiveness of both treatments in controlling internal nutrient loading and in the mitigating algal bloom episodes, their negative effects on biota have to be seriously taken into account.
El texto completo de este trabajo en Clic ¡
• 2021/ B.J. Cardinale, R. Bier, C. Kwan
TiO2 nanoparticles for the remediation of eutrophic shallow freshwater systems: Efficiency and impacts on aquatic biota under a microcosm experiment
Nanoparticulate mineral UV filters, such as titanium dioxide(TiO2) nanocomposites,are being increasingly used in sunscreens as an alternative to organic UV filters. However,there is still a lack of under standing regarding their fate and behavior in aquatic environments and potential environmental impacts after being released from a bather’s skin during recreational activities.
In this work,we assessed the release, fate,and transformation of two commercial nanocomposite TiO2 UV filters, one hydrophobic and one hydrophilic,in ultrapure water and simulated fresh-and sea water. The hydrophobicTiO2 nanocomposite,T-SA, was coated with a primary Al2O3 photopassivation layer and a secondary stearic acid layer,while the hydrophilicTiO2 nanocomposite,T-SiO2, was coated with a singleSiO2 photopassivation layer. The influence of the sunscreen formulation was examined by dispersing the TiO2 nanocomposites in their typical continuous phase(i.e.,oilforT-SA and water for T-SiO2) before introduction in to the aqueous system. After 48 h of aqueous aging and 48 h of settling, 88 e 99% of the hydrophobicT-SA remained floating on top of the water column in all aqueous systems. On the other hand, 100% of the hydrophilicT-SiO2 settled out of the water column in the fresh-and sea waters. With respect to the photo passivation coatings,no loss of the T-SAAl2O3 layer was detected after aqueous aging, but99e100% dissolution of the SiO2 layer on theT-SiO2 nanocomposite was observed after 48 h in the fresh-and sea waters. This dissolution left behind T-SiO2 by-products exhibiting a photocatalytic activity similar to that of barerutile TiO2. Overall,the results demonstrated that the TiO2 surface coating and sunscreen formulation type drive environmental behavior and fate and that loss of the passivation layer can result in potentially harmful, photo active by products. These insights will help guide regulations and assist manufacturers in developing more environmentally safe sunscreens.
El texto completo de este trabajo en Clic ¡
• 2020 / P.L. Sanches, L.R. Oliveira, R. Cruz, D. Cigaran, M. Lorencini, J.M. Granjeiro, A.R. Lopes
Effects of TiO2 nanoparticles on the growth and metabolism of three species of freshwater algae
Titanium dioxide nanoparticles (TiO2 NPs) are regularly used in sunscreens because of their photo protective capacity. The advantage of using TiO2 on the nanometer scale is due to its transparency and better UV blocking efficiency. Due to the greater surface area/volume ratio, NPs become more (bio)-reactive giving rise to concerns about their potential toxicity. To evaluate the irritation and corrosion of cosmetics, 3D skin models have been used as an alternative method to animal experimentation. However, it is not known if this model is appropriate to study skin irritation, corrosion and phototoxicity of nanomaterials such as TiO2 NPs. This systematic review (SR) proposed the following question: Can the toxicity of TiO2 nanoparticles be evaluated in a 3D skin model? This SR was conducted according to the Preliminary Report on Systematic Review and Meta-Analysis (PRISMA). The protocol was registered in CAMARADES and the ToxRTool evaluation was performed in order to increase the quality and transparency of this search.
In this SR, 7 articles were selected, and it was concluded that the 3D skin model has shown to be promising to evaluate the toxicity of TiO2 NPs. However, most studies have used biological assays that have already been described as interfering with these NPs, demonstrating that misinterpretations can be obtained. This review will focus in the possible efforts that should be done in order to avoid interference of NPs with biological assays applied in 3D in vitro culture.
El texto completo de este trabajo en Clic ¡
D/ REDES TRÓFICA Y RESPUESTAS DE LAS COMUNIDADES
• 2009/ Iwona Jasser, Iwona Kostrzewksa-Slakowska, Jolanta Ejsmont-Karabin, Krystyna Kalinowska; Teresa Eeglenska
Autotrophic versus heterotrophic production and components of trophic chain in humic lakes: the role of microbial communities
The ratio and rates of autotrophic and heterotrophic pathways of organic matter cycles constitute the basic functions of aquatic ecosystem and humic lakes are unique in this respect. The autotrophic and heterotrophic production, the food web structure and the role of microbial communities in three humic lakes (area 1.3–9.2 ha) were studied. The abundance of bacteria, autotrophic picoplankton (APP), nanoflagellates (NF), ciliates, phytoplankton, rotifer and crustacean zooplankton as well as chlorophyll a and primary (14C method) and bacterial production (3H–thymidine method) were measured. The lakes differed in humic matter content, water colour, pH and hydrology. Two lakes were acidic (pH 5.2–4.9) with different dissolved organic carbon (DOC) content: oligo/mesohumic – 7.1 mg C L–1 , and polyhumic lake – 21 mg C L–1. Due to draining of surrounding meadows, the third lake – formerly humic – experienced changes in the hydrological regime together with liming and fertilisation. Despite low DOC, the oligohumic lake resembled a low productive, typically humic, acidic lake with dominating bacterial production. The lake was characterised by the highest crustaceans biomass and very variable chlorophyll a concentration (between 1.5 and 71 mg Chl a m–3). The polyhumic lake had the highest mean and maximal chlorophyll a content but the lowest crustacean biomass, and functioned more like a eutrophic lake. The formerly humic lake had lost probably most of its humic features and experienced a eutrophication process that resulted in a food web structure typical of a shallow eutrophic pond-like environment. The mean chlorophyll a concentration there was at the same level as in an oligohumic lake, but the variability was much lower. This lake can be considered as an example of the posthumic lakes abundant in the managed wetland regions. Microbial communities were numerous in both humic lakes, with bacteria prevailing in microbial biomass in the oligo-humic and APP in the polyhumic lake. In the former humic lake the microbial communities, especially APP, seemed to play a lesser role, while the whole planktonic food web was more balanced. The results demonstrated that uncontrolled drainage and reclamation of wetland can be detrimental to biodiversity of small, mid-forest lakes. Although biodiversity in almost all plankton groups was the highest in the posthumic lake but this lake lacked rare species typical of humic acidic lakes like: Gonyostomum semen, Dictyosphaerium sphagnale from phytoplankton or Holopedium gibberum from crustacean zooplankton. Instead eurytopic species, common in eutrophic waters, were present.
El texto completo de este trabajo en Clic ¡
• 2015/ K. Sparber, C. Dalton, E. de Eyto, E. Jennings, D. Lenihan; F. Cassina
Contrasting pelagic plankton in temperate Irish lakes: the relative contribution of heterotrophic, mixotrophic, and autotrophic components, and the effects of extreme rainfall events
The mobilisation of energy from allocthonous carbon by heterotrophic bacterioplankton can be proportionally more important than autotrophic production in humic lakes. Moreover, increasing levels of dissolved organic carbon (DOC) in many aquatic systems linked to increases in precipitation, which in turn may be related to changing climate, mean that this heterotrophic component of the food web may play an increasing role in the overall transfer and production of energy, particularly within peatland catchments. While such catchments are common in the temperate northwest Atlantic regions of Europe, studies describing the seasonal dynamics of the heterotrophic, mixotrophic, and autotrophic components of their aquatic food webs are rare. In this study, the biomass of these pelagic components was enumerated
over 1 year in 2 oligotrophic lakes, both situated in peatland catchments in the west of Ireland but with contrasting DOC concentrations. Bacterial biomass dominated the pelagic food web of the more humic lake, Lough Feeagh, while autotrophic phytoplankton biomass was greatest in the clearwater lake, Lough Guitane. The biomass of potentially mixotrophic flagellates was also slightly larger in the Lough Guitane, while phagotrophic ciliate biomass was comparable between the 2 lakes. An extreme precipitation event led to a significant increase in bacterial biomass while simultaneously depressing autotrophic production for several months in the humic lake. Extreme precipitation in the clearwater lake also depressed autotrophic production but did not give rise to significant increases in bacterial biomass.
This quantification of autotrophic, mixotrophic, and heterotrophic components provides a vital first step in understanding how pelagic communities contribute to net ecosystem productivity, and thus how Irish peatland lakes may be affected by projected climate changes.
El texto completo de este trabajo en Clic ¡
• 2010/ Straile D. & Müller H.
Response of Bosmina to climate variability and reduced nutrient loading in a large lake
The long-term dynamics of the cladoceran Bosmina spp. were analysed in Lake Constance during the study period 1979–1998. During this period the lake ecosystem has been influenced strongly by changes in nutrient inflow (oligotrophication) and by climate variability associated with the North Atlantic Oscillation. Bosmina abundances declined strongly during the study period presumably as an indirect consequence of the reduced P loading of the lake. A detailed seasonally resolved analysis of Bosmina dynamics revealed that its abundance decline occurred throughout the year with the exception of the spring period. The lack of a population decline during spring may be attributed to the seasonal absence of the factor, e.g., food limitation and/or predation control by invertebrates causing the population decline. Additionally, climate variability had its strongest influence on Bosmina dynamics during spring and large climate-associated variability of Bosmina may have decreased the power to detect a significant reduction in spring Bosmina abundances with oligotrophication. However, when we account for the confounding influence of climate variability, the effects of oligotrophication are revealed more clearly also during the spring period. Likewise, the detectability of the influence of climate variability on spring Bosmina dynamics increases when accounting for the reduction of abundances in the course of oligotrophication.
El texto completo de este trabajo en Clic ¡
• 2012/ Jan Karlsson, Martin Berggren, Jenny Ask, Pär Byström, Anders Jonsson, Hjalmar Laudon; Mats Jansson
Terrestrial organic matter support of lake food webs: Evidence from lake metabolism and stable hydrogen isotopes of consumers
We quantified the utilization of terrestrial organic matter (OM) in the food web of a humic lake by analyzing the metabolism and the consumers’ stable isotopic (C, H, N) composition in benthic and pelagic habitats. Terrestrial OM inputs (3 g C m22 d21) to the lake greatly exceeded autochthonous OM production (3 mg C m22 d21) in the lake. Heterotrophic bacterial growth (19 mg C m22 d21) and community respiration (115 mg C m22 d21) were high relative to algal photosynthesis and were predominantly (. 85%) supported by terrestrial OM in both habitats. Consequently, terrestrial OM fueled most (85%) of the total production at the base of the lake’s food web (i.e., the sum of primary and bacterial production). Despite the uncertainties of quantitatively estimating resource use based on stable isotopes, terrestrial OM clearly also supported around half the zooplankton (47%), macrozoobenthos (63%), and fish (57%) biomass. These results indicate that, although rates of terrestrial OM inputs were around three orders of magnitude greater than that of autochthonous OM production, the use of the two resources by higher trophic levels was roughly equal. The disproportionally low reliance on terrestrial OM at higher trophic levels, compared with its high rates of input and high support of basic biomass production in the lake, suggests that autochthonous resources could not be completely replaced by terrestrial resources and indicates an upper limit to terrestrial support of lake food webs.
El texto completo de este trabajo en Clic ¡
• 2019/ Boggero A., Zaupa S., Mussazi S., Rogora M., Dumnicka E. & Lami A.
Environmental factors as drivers for macroinvertebrate and diatom diversity in Alpine lakes: New insights from the Stelvio National Park (Italy).
Information on the biodiversity of high altitude lakes in the Stelvio National Park was scarce and fragmentary, in most cases limited to a few studies on a single biological issue. To fill this gap, a multidisciplinary research program was established in 2011 to investigate macroinvertebrates, diatoms, and water chemistry in 8 high altitude lakes within the boundaries of the Park (Rhaetian Alps, Eastern Alps). The results of this study were compared with data on biological assemblages and chemical parameters of Alpine lakes in the Pennine-Lepontine Alps (Western Alps), to evaluate the role of local drivers with respect to regional ones. This comparison was possible thanks to the adoption of standardized sampling methodologies developed since the ’90s by the National Research Council-Water Research Institute (Verbania), in collaboration with several European Research centers. Despite located in a restricted geographical area, the lakes of the Stelvio National Park showed a high variability of chemical composition, and of sensitivity to acidification, lower than that of the Pennine-Lepontine Alpine lakes. Macroinvertebrate and diatom taxa were ubiquitous and frequent along the Alps, and mainly represented by cold-stenothermal species. Richness, Shannon, Simpson, and Pielou indices applied to phyto- and zoobenthos highlighted significantly lower values in Stelvio National Park lakes than in those of Pennine-Lepontine for macroinvertebrates, while no significant differences were found for diatoms. Two groups of lakes were identified by Cluster Analysis, mainly on the basis of major ion concentrations. Canonical Correspondence Analysis showed that the macroinvertebrate assemblage of the lakes studied is driven mainly by altitude and lake surface, and, to a lesser extent, by nutrient content. On the contrary, pH and acid-related variables played a secondary role for diatoms, while nutrients and, more in general, ionic content had significant effects on their species composition. Overall, the results of this first investigation showed that the high elevation of these lakes affects their macroinvertebrate assemblages, while their diatom communities are comparable throughout the Alps.
El texto completo de este trabajo en Clic ¡
• 2019/ Karpowicz M. & Jolanta E.
Influence of environmental factors on vertical distribution of zooplankton communities in humic lakes.
The influence of vertical environmental gradients on zooplankton communities was studied in five humic lakes with the high availability of food resources (phytoplankton and bacterioplankton) and low fish pressure. The factors that inhibit the development of large zooplankton in humic lakes are currently widely debated. We have found that relatively productive humic lakes do not offer many niches for zooplankton because of the sharp thermal gradient which results in a shallow layer of oxygenated waters. The results of this study indicated that different taxonomic groups of zooplankton are determined by a different set of environmental variables. This phenomenon explains very low species richness of zooplankton and a possibility of their coexistence in the narrow oxygenated layer.We concluded that due to sharp thermal gradient in humic lakes biomass of herbivores may be reduced which could promote development of phytoplankton.
El texto completo de este trabajo en Clic ¡
• 2013/ Korosi J.B., Kurek J. & Smol J.P.
A review on utilizing Bosmina size structure archived in lake sediments to infer historic shifts in predation regimes.
Zooplankton are considered excellent indicators of aquatic food web structure, due to their role as grazers on primary producers and their sensitivity to predation by both planktivorous fish and invertebrates. Several key zooplankton taxa also leave identifiable remains that are often well-preserved in lake sediments, providing an opportunity to track changes in predation pressure over timescales of decades to thousands of years. For example, the small-bodied cladoceran zooplankter Bosmina (Branchiopoda, Crustacea) is often highly abundant in lake sediments, and because Bosmina often undergoes cyclomorphosis in response to fish and invertebrate predation, measurements of subfossil Bosmina features can be indicative of predation regime shifts. This review focuses on Bosmina cyclomorphic responses to varying predation regimes and the application of these principles to Bosmina subfossil remains to better understand long-term ecological changes occurring in lakes. We conclude that subfossil Bosmina size structure is a promising indicator of historic changes in predation pressure in response to fish introductions/extirpations/population dynamics and other anthropogenic disturbances. Size measurements of Bosmina subfossils can often complement traditional zooplankton community assessments and provide critical insight into how predator–prey dynamics change as a result of environmental stressors, as well as the timescale of response to historic predation regime shifts.
El texto completo de este trabajo en Clic ¡
E/ COMPOSICIÓN QUÍMICA Y DINÁMICA GEOQUÍMICA
• 1994/ Pessner R.; Jordi Catalan
Chemical composition of lakes in crystalline basins: a combination of atmospheric deposition, geologic background, biological activity and human action
Non-sedimentary basins are characterized by the lack of easily soluble minerals and, as a consequence, by holding soft-waters. Regional limnology has shown that, besides biogeographical reasons, alkalinity is one of the main factors determining the distribution of organisms. In soft-water areas, slight changes in mineral content strongly affect the composition of aquatic communities. Anthropogenic impacts are predominant in eutrophied marine and freshwater environments and the chemical composition of many soft-water lakes in the northern hemisphere is largely influenced by acids emitted from the burning of fossil fuels. Eutrophication and acidification have some effects in common, such as changes in species composition and the extinction of sensitive organisms. Nitrogen compounds have become an issue of research in the eutrophication of marine environments, and nitric acid in combination with NH4+ at present exceeds the importance of sulphuric acid in deposition chemistry.
El texto completo de este trabajo en Clic ¡
• 1951/ Stommel H.
Streaks on natural water surfaces
I was very much interested to see Mr. A. K. Totton’s photographs of markings on the water because recently I have been trying to collect as much information about such phenomena as possible. I enclose two photographs which may interest the readers of Weather; one, showing ‘ venous streaks ’ on the surface of the Great Salt Lake of Utah, was kindly given to me by Prof. A. J. Eardley of the University of Utah; the other, a picture of the Banana River in Florida, shows a remarkable development of «parallel streaks». Most natural bodies of water have a streaky appearance which results from a natural process, although artificial streaks are also frequently observed. There has been quite a difference of opinion in the literature as to the nature of the process which produces streaks. I am personally inclined to admit that under certain circumstances any one of the processes suggested may account for them ; to attribute all streaks to the same mechanism would be a great mistake. I should like, therefore, to review briefly what little material there is in the literature about these streaks on the surface of natural bodies of water.
El texto completo de este trabajo en Clic ¡
• 2016/ F. Stefani, F. Salerno, D. Copetti, D. Rabuffetti, L. Guidetti, G. Torri, A. Naggi, M. Iacomini, G. Morabito & L. Guzzella
Endogenous origin of foams in lakes: a long-term analysis for Lake Maggiore (northern Italy)
The formation of foams on lakes is a complex phenomenon whose origin is often hardly identifiable. Recently (2007, 2008, and 2010) foam episodes started to occur in Lake Maggiore, northern Italy. The present work aimed to verify the hypothesis of an endogenous-natural origin of these foams, driven by trophic or climatic changes. To this purpose, a long-term (2000–2013) analysis of phytoplankton biovolumes, meteorological, and hydrological data has been performed together with the chemical characterization of foams. Foams resulted of endogenous origin and likely related to phytoplankton biomass degradation. Data analysis highlighted atypical warm temperature and residual lake stratification in winter in two of the three years of foam events, coupled with exceptional Bacyllariophyceae blooms in spring. Tabellaria flocculosa mostly contributed in terms of biomass in 2007 and 2008, but not in 2010; thus overall algal biomass seemed a better predictor of the risk of foam formation. Foam events occurred from July to December, driven by atypically windy conditions, and congruently with the time needed to degrade biomass into surface-active compounds. A co-occurrence of different factors resulted essential to generate foams, and climate changes likely contribute to enhance their occurrence in Lake Maggiore.
El texto completo de este trabajo en Clic ¡
• 2011/ K. Schilling & M. Zessner
Foam in the aquatic environment
Foams are ubiquitous in the environment, commonly seen as discoloured patches on streams, rivers, lakes and sea water. They often are assumed to be anthropogenic in origin as they are aesthetically unpleasant, yet they frequently appear in pristine environments indicating a natural origin. In contrast to “hidden” chemical pollution, e.g. heavy metals, pesticides etc. the visibility of foam alarms the public. To derive more information on foam in freshwaters and marine ecosystems, a literature review was performed. Alongside with some basic considerations on the formation of foam, on methods to measure foam formation and on the legal aspects of foam on surface waters, the ecological importance of foam in the aquatic environment is discussed in this paper.
El texto completo de este trabajo en Clic ¡
• 2019/ Llorens-Marès T., Catalan J., Casamayor E.O.
Taxonomy and functional interactions in upper and bottom waters of an oligotrophic high-mountain deep lake (Redon, Pyrenees) unveiled by microbial metagenomics
High mountain lakes are, in general, highly sensitive systems to external forcing and good sentinels of global environmental changes. For a better understanding of internal lake processes, we examined microbial biodiversity and potential biogeochemical interactions in the oligotrophic deep high-mountain Lake Redon (Pyrenees, 2240m altitude) using shotgun metagenomics. We analyzed the two ends of the range of environmental conditions found in Lake Redon, at 2 and 60 m depths. Bacteria were the most abundant component of the metagenomic reads (N90%) and the diversity indices of both taxonomic (16S and 18S rRNA) and functional (carbon-, nitrogen-, sulfur-, and phosphorous-cycling) related geneswere higher in the bottom dark layer than in the upper compartment. A marked segregation was observed both in biodiversity and in the dominant energy and biomass generating pathways between the extremes. The aerobic respiration was mainly dominated by heterotrophic Burkholderiales at the top and Actinobacteria and Burkholderiales at the lake bottom. The potential for an active nitrogen cycle (nitrogen fixation, nitrification, nitrite oxidation, and nitrate reduction) was mainly found at 60 m, and potential for methanogenesis, anaerobic ammonia oxidation and dissimilatory sulfur pathways were only observed there. Some unexpected and mostly unseen energy and biomass pathways were found relevant for the biogeochemical cycling in lake Redon, i.e., those related to carbon monoxide oxidation and phosphonates processing.We provide a general scheme of the main biogeochemical processes that may operate in the sentinel deep Lake Redon. This framework may help for a better understanding of the whole lake metabolism.
El texto completo de este trabajo en Clic ¡
F/ LAGOS COMO SENSORES AMBIENTALES EN EL HOLOCENO
• 1993/ Toro M.; Flower. R.J.; Rose N.L.; Stevenson A.C.
The sedimentary record of the recent history in a high mountain lake in central Spain
El texto completo de este trabajo en Clic ¡
• 2009/ Jordi Catalan; Sergi Pla; Joan García; Lluís Camarero
Climate and CO2 saturation in an alpine lake throughout the Holocene
This study shows that diatom sediment records can be used to investigate the long-term inorganic carbon dynamics in oligotrophic and poorly acid-buffered lakes. Using a training set of 115 high-mountain lakes in the Pyrenees, we found that both alkalinity and potential hydrogen (pH) independently explained some of the variability in diatom assemblages. Transfer functions for both variables were developed and applied to a Holocene record from Lake Redon and CO2 changes calculated. CO2 saturation broadly followed alkalinity, which in turn was related to summer and autumn air-temperature fluctuations. In general, warmer climate during the ice-free period led to higher supersaturation, due to increased alkalinity, which facilitated retention of CO2 from respiration, and decreased primary production (assessed by diatom fluxes). Only during the early Holocene, there were periods of extreme undersaturation, corresponding to cold periods of low alkalinity (<20 microequivalents per liter [µeq L−1]), and suggesting carbon limitation of primary production. The winter and spring climate, which determines the ice cover duration, appears to be relevant for CO2 saturation only during periods when the organic-matter content of the sediments was low (<22%). Longer periods of ice cover led to lower lake CO2 saturation, suggesting that the ice cover influence on internal nutrient loading may regulate lake productivity fluctuations under low allocthonous nutrient and organic-matter inputs. Alkalinity ~20 µeq L−1 and sediment organic matter ~22% appear as critical thresholds in the way lake CO2 levels respond to climate fluctuations.
El texto completo de este trabajo en Clic ¡
• 2009/ Craig E. Williamson; Jasmine E. Saros; Warwick F. Vincent; John P. Smol
Lakes and reservoirs as sentinels, integrators, and regulators of climate change
Climate change is generating complex responses in both natural and human ecosystems that vary in their geographic distribution, magnitude, and timing across the global landscape. One of the major issues that scientists and policy makers now confront is how to assess such massive changes over multiple scales of space and time.
Lakes and reservoirs comprise a geographically distributed network of the lowest points in the surrounding landscape that make them important sentinels of climate change. Their physical, chemical, and biological responses to climate provide a variety of information-rich signals. Their sediments archive and integrate these signals, enabling paleolimnologists to document changes over years to millennia. Lakes are also hot spots of carbon cycling in the landscape and as such are important regulators of climate change, processing terrestrial and atmospheric as well as aquatic carbon. We provide an overview of this concept of lakes and reservoirs as sentinels, integrators, and regulators of climate change, as well as of the need for scaling and modeling these responses in the context of global climate change. We conclude by providing a brief look to the future and the creation of globally networked sensors in lakes and reservoirs around the world.
El texto completo de este trabajo en Clic ¡
• 2009/ Adrian A., M. O’Reilly C., Zagarese H., Stephen B. Baines, Dag O. Hessen, Wendel Keller, David M. Livingstone, Ruben Sommaruga, Dietmar Straile, Ellen Van Donk, Gesa A. Weyhenmeyer & Monika Winder
Lakes as sentinels of climate change
While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
El texto completo de este trabajo en Clic ¡
• 2007/ P. Rosén; D. Hammarlund
Effects of climate, fire and vegetation development on Holocene changes in total organic carbon concentration in three boreal forest lakes in northern Sweden
Near infrared spectroscopy (NIRS), diatoms, pollen, charcoal, loss-on-ignition (LOI), and nutrient elements in lake sediments were used to assess important factors controlling Holocene hanges in the total organic carbon (TOC) concentration, pCO2, color and pH of lake water in three boreal forest lakes in northern Sweden. The results suggest that mire formation, fire frequency and humidity are the most important forcing factors on millennial timescales. Mires produce humic acids that become available to the lakes, whereas fires may reduce the pool of carbon in the catchments, and humidity controls the transportation of allochthonous carbon into the lakes. Vegetation development and temperature as sole factors are of minor importance
for the TOC concentrations in these lakes on a millennial timescale. Two of the sites indicate that liming and possibly fish introduction and rotenone treatment in recent time has led to increased TOC, color and pH in the lake water, and changed the diatom community composition to an assemblage that has never been present before. Given the predicted climate change scenario that suggests a more humid climate, expanding mires and less frequent fires, our paleolimnological data suggest that TOC concentrations can be expected to increase in boreal forest lakes in the future. Since supersaturation and emission of CO2 from lakes is correlated to the TOC concentration of lake water, higher TOC concentrations may lead to increased emission of CO2 from lakes to the atmosphere.
El texto completo de este trabajo en Clic ¡
• 2008 / Manuel Toro; Antonio Camacho; Eugenio Rico; Carlos Rochera; David Velázquez; José Antonio Domínguez; Antonio Quesada
Implicaciones del cambio climático en el funcionamiento de los ecosistemas antárticos: los lagos como centinelas de la variación ambiental
Entre las Islas Shetland del Sur, en la Antártida marítima, se encuentra la Isla Livingston, en cuyo extremo oeste se localiza una de las zonas con mayor biodiversidad no marina de la Antártida, y una de las concentraciones más importantes de cuerpos de agua continentales en toda la Antártida: la Península de Byers. En la región de la Península Antártica se están detectando los mayores incrementos de temperatura del Planeta en las últimas décadas como consecuencia del calentamiento global (Sun y Hansen, 2003). Por estos motivos, el proyecto LIMNOPOLAR, con un marcado carácter multidisciplinar, estudia el funcionamiento de estos ecosistemas acuáticos y su posible papel como sensores del cambio climático. La investigación llevada a cabo en esta Zona de Especial Protección de la Antártida (ASPA nº 126) cubre aspectos relacionados con la limnología básica, la hidrología, los ciclos biogeoquímicos, la biodiversidad y sus redes tróficas, la meteorología, la paleoecología y la teledetección, entre otros. Los resultados previos que van obteniéndose en el estudio apuntan a una gran dependencia de todos los procesos ecológicos e interrelaciones entre la biota y el medio abiótico, respecto a variables climáticas como la temperatura y la precipitación. El objetivo final del proyecto es elaborar un modelo predictivo basado en los estudios actuales y en las reconstrucciones paleoecológicas del clima pasado, que permitiría estimar los posibles efectos del cambio climático y la respuesta de estos ecosistemas únicos en el Planeta.
El texto completo de este trabajo en Clic ¡
• 2018 / Meritxell Batalla, Miquel Ninyerola, Jordi Catalan
Digital long‐term topoclimate surfaces of the Pyrenees mountain range for the period 1950–2012
Long‐term climate data accounting for high‐spatial variability and detailed topographic effects are crucial for research and management in complex terrains such as mountain ranges. Here, we introduce the Pyrenean Digital Climate Atlas based on data from around 400 weather stations located across the range during the 1950–2012 period. Average monthly, seasonal, and annual temporal resolutions are provided for 30‐m spatial resolution surfaces. Local heterogeneity was considered, integrating meteorological station data, high‐quality terrain information (altitude, latitude, distance to the sea, and solar potential radiation) and multivariate regression modelling in a Geographical Information System. Climate surfaces of air temperature (minimum, maximum, and mean) and precipitation were obtained and used to derive maps of bioclimatic interest such as potential evapotranspiration, water availability, and growing degree‐days. Metadata are provided in XML standard format (ISO 19139) with all the usual fields and quality indicators for each map, with an RMSE ranging from 0.7 to 1.2°C and 11 to 15 mm for air temperature and precipitation maps respectively. The Atlas is available in Geo- TIFF format at the ZENODO repository.
El texto completo de este trabajo en este link Clic ¡
• 2017 / García-Criado F., Martínez-Sanz C., Valladares L.F. & Fernández-Aláez C.
Environmental and spatial patterns as drivers of litoral macroinvertebrate assemblages in patchily distributed mountain lakes: Contribution to typology design
Biological assemblages are affected by both environmental and spatial processes. Spatial autocorrelation can be specially marked in discrete ecosystems patchily distributed over a large region (e.g., lakes arranged in districts). Lake typologies are exclusively based on environmental features, but we hardly know to what extent spatial patterns can hinder their implementation. We analysed the role of environmental factors and spatial autocorrelation in shaping littoral macroinvertebrate communities of 51 mountain lakes from a large Spanish region in order to test: 1) the suitability of the variables currently used to construct typologies; 2) the influence of spatial patterns on typology implementation. Biologically meaningful types of lakes were created and described by means of cluster analysis (Jaccard index) and multiple discriminant analysis. Water permanence, substrate type and vegetation were the main drivers of the assemblage composition. The cluster analysis and Mantel tests showed that spatial patterns did not generally hamper recognizing lake types. Only in the district with lakes closest to each other (Sanabria Natural Park), spatial autocorrelation was strong enough to overcome the effects of some factors (substrate type), but not others(water permanence).
El texto completo de este trabajo en este link Clic ¡
