Calcio, fósforo y metales del sedimento de la laguna de la Massona (Girona)

Es presenten els resultats d'una investigació preliminar de la composició química dels sediments de la Massona, una llacuna costanera dels aiguamolls de l'Empordà. Hom hi va analitzar el calci, ferro, manganes, fosfor, plom i crom. Els valors observats concorden amb estudis previs de les característiques de les aigües. L'hipolímnion anoxic de la llacuna fa que en el sediment hi hagi un empobriment relatiu en calci (concentració mitjana, 79,9 mg/g), manganès (concentracióo mitjana, 286 ppm) i fòsfor (concentració mitjana, 752 ppm), mentre que el ferro i el crom hi són augmentats (concentracions mitjanes del 39,1 % i de 58,7 ppm, respectivament). Els perfils verticals del ferro i del manganès són oposats: el ferro augmenta en profunditat i el manganès disminueix. Ambdós elements presenten entre ells una correlació negativa (r=-0,50). Aquests resultats indiquen que les condicions reduïides en el fons d'aquesta llacuna són relativament constants, i que en el passat hi ha hagut un canvi en les entrades, probablement degut a una menor influència de l'aigua de mar.This paper reports the results of an exploratory investigation of the chemical composition of sediments from La Massona, a coastal lagoon located in the Aiguamolls de l'Empordà area (salt marshes in Girona, Spain). Calcium, iron, manganese, phosphorus, lead and chromium were analized. The observed values were consistent with previous studies of water characteristics. Anoxic hypolimnion in the lagoon caused a relative impoverishment of the sediment in calcium (mean concentration, 79.9 mg/g), manganese (mean concentration, 286 ppm) and phosphorus (mean concentration, 752 ppm), whereas iron and chromium increased (mean concentrations, 3.91 % and 58.7 ppm respectively). Iron and manganese vertical profiles were opposed: iron rose in depth and manganese decreased. Both elements showed a negative correlation between them ( r=-0.50). Results suggest that reduced conditions in the bottom are quite constant in the lagoon, and a change in the inputs has taken place in the past, probably because of a lower influence of seawater

Subsurface zones in intermittent streams are hotspots of microbial decomposition during the non-flow period

The microbial decomposition of organic matter is a fundamental ecosystem process that transforms organic matter and fuels detritus-based food webs, influencing biogeochemical cycles such as C-cycling. The efficiency of this process can be compromised during the non-flow periods of intermittent and ephemeral streams (IRES). When water flow ceases, sediments represent the last wet habitat available to microorganisms and may play an important role in sustaining microbial decomposition. However, despite the increasing prevalence of IRES due to climate change and water abstraction, it is unclear to what degree the subsurface habitat can sustain microbial decomposition during non-flow periods. In order to gather information, we selected 20 streams across Catalonia (Spain) along a gradient of flow intermittency, where we measured microbial decomposition and fungal biomass by placing wood sticks in both the surface and subsurface zones (15 cm below the streambed) over the course of one hydrological year. Our results showed that microbial decomposition and fungal biomass were consistently greater in the subsurface zone than in the surface zone, when intermittency increased. Although flow intermittency was the main driver of both microbial decomposition and fungal biomass, phosphorus availability in the water, sediment C:N ratio and sediment grain size also played relevant roles in surface and subsurface organic matter processing. Thus, our findings demonstrate that although the OM processing in both zones decreases with increased intermittency, the subsurface zone made an important contribution during the non-flow periods in IRES. Therefore, subsurface activity during non-flow periods has the potential to affect and maintain ecosystem functioning

Elemental ratios in sediments as indicators of ecological processes in Spanish reservoirs

Reservoir sediments are important archives of biogeochemical data, reflecting ecological processes that occur at the watershed system. In this paper, a preliminary study of the limnological significance of major element composition and element ratios in sediments of Spanish reservoirs is presented, by analysing two data-sets from different limnological regions. Reservoirs from Eastern and Western Spain present significant differences in the chemical composition of their sediments: higher average values for calcium and magnesium appear in the Eastern reservoirs, while, in Western Spain, higher mean values are found for alumino-silicate elements (i.e. silicon, aluminium, and potassium), iron and phosphorus. Meaningful ratios are Si/Al and Si/K, that are closely related to energy transport in sedimentary catchments, whereas in siliceous catchments Si/Al is an indicator of chemical weathering. Ca/Al ratio appears related to water mineralization, and, in the Eastern Region, the slope of the regression line between Ca/Al and conductivity reflects catchment mineralogy. In superficial sediments from both Eastern and Western regions, Fe/Al is linked to the authigenic precipitation of iron oxides and appears closely related to sedimentary phosphorus accumulation above background levels.El sedimento de los embalses constituye un importante registro de datos biogeoquímicos, ya que refleja los procesos ecológicos que tienen lugar en el conjunto de la cuenca hidrográfica. A partir del análisis de dos conjuntos de datos obtenidos en distintas regiones limnológicas, se presenta una aproximación preliminar al significado limnológico de la composición química y los cocientes elementales en el sedimento de los embalses españoles. Las regiones Este y Oeste de la Península muestran diferencias significativas en cuanto a composición química del sedimento: los mayores valores promedio en la región Este corresponden a la concentración de calcio y magnesio, mientras que en la región Oeste, los mayores valores medios corresponden a los elementos asociados a los alumino-silicatos (aluminio, silicio y potasio), hierro y fósforo. Los cocientes elementales con mayor significado son: Si/K y Si/Al estrechamente relacionados con la energía de transporte en la región calcárea, mientras que en la región silícica Si/Al es un indicador del proceso de meteorización química. Ca/Al se encuentra asociado a la mineralización del agua, y en la región Este la pendiente de la recta de regresión entre Ca/Al y la conductividad del agua refleja la mineralogía de la cuenca. En ambas regiones, el cociente Fe/Al en el sedimento superficial indica la precipitación endógena de óxidos de hierro y aparece estrechamente asociado a la acumulación de fósforo sedimentario por encima del nivel basal

Modern Analogue Approach Applied to High-Resolution Varved Sediments-A Synthesis for Lake Montcortès (Central Pyrenees)

In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of di erent modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Di erent biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortès as a case study and proposing new working hypotheses for future research

El aprendizaje adaptativo de los estudiantes de un Grado de nueva creación: Análisis de su actividad en el Campus Virtual-UB

La docencia presencial de la Univ. Barcelona se apoya en su Campus virtual. Para promover el aprendizaje adaptativo, hemos analizado los Recursos/Actividades (número, tipo y frecuencia de uso) de 3 cohortes del Grado de Ciencias del Mar (30 Informes de actividad en total y 10 Registros de uso seleccionados). Predominan los Recursos (87%), pero se interactúa más en las Actividades. El análisis de los Registros ha permitido relacionar los resultados con el rendimiento, género u opcionalidad

Calcio, fósforo y metales del sedimento de la laguna de la Massona (Girona)

Es presenten els resultats d'una investigació preliminar de la composició química dels sediments de la Massona, una llacuna costanera dels aiguamolls de l'Empordà. Hom hi va analitzar el calci, ferro, manganes, fosfor, plom i crom. Els valors observats concorden amb estudis previs de les característiques de les aigües. L'hipolímnion anoxic de la llacuna fa que en el sediment hi hagi un empobriment relatiu en calci (concentració mitjana, 79,9 mg/g), manganès (concentracióo mitjana, 286 ppm) i fòsfor (concentració mitjana, 752 ppm), mentre que el ferro i el crom hi són augmentats (concentracions mitjanes del 39,1 % i de 58,7 ppm, respectivament). Els perfils verticals del ferro i del manganès són oposats: el ferro augmenta en profunditat i el manganès disminueix. Ambdós elements presenten entre ells una correlació negativa (r=-0,50). Aquests resultats indiquen que les condicions reduïides en el fons d'aquesta llacuna són relativament constants, i que en el passat hi ha hagut un canvi en les entrades, probablement degut a una menor influència de l'aigua de mar.This paper reports the results of an exploratory investigation of the chemical composition of sediments from La Massona, a coastal lagoon located in the Aiguamolls de l'Empordà area (salt marshes in Girona, Spain). Calcium, iron, manganese, phosphorus, lead and chromium were analized. The observed values were consistent with previous studies of water characteristics. Anoxic hypolimnion in the lagoon caused a relative impoverishment of the sediment in calcium (mean concentration, 79.9 mg/g), manganese (mean concentration, 286 ppm) and phosphorus (mean concentration, 752 ppm), whereas iron and chromium increased (mean concentrations, 3.91 % and 58.7 ppm respectively). Iron and manganese vertical profiles were opposed: iron rose in depth and manganese decreased. Both elements showed a negative correlation between them ( r=-0.50). Results suggest that reduced conditions in the bottom are quite constant in the lagoon, and a change in the inputs has taken place in the past, probably because of a lower influence of seawater

Chemical composition of the small coastal lagoons of the Mediterranean Spanish littoral

About sixty small water bodies (coastal lagoons, marshes, salt pans, channels, springs, etc.) of the Spanish Mediterranean coast were sampled seasonally for one year (1979-1980), in order to study different aspects of their chemical composition. The concentrations of major ions (alkalinity, Cl-, Ca2+, Mg2+, Na+, and K+), nutrients (N.NO-3, N.NO2-, TRP and Si), oxygen and pH were determined for this purpose. The salt concentrations measured range between 0.4 and 361.3 g l-1. The samples have been divided into four classes of salinity (in g l-1): Cl, S 40. Within these classes, the pattern of ionic dominance recorded is remarkably constant and similar to that found in most coastal lagoons (Cl- > So42- > Alk., for the anions, and Na+ > Mg2+ > Ca2+ > K+, for the cations), although other models occur especially in the first class. The dominance of Na+ and Cl-, as well as the molar ratios Mg2+/Ca2+ and Cl- / SO42- ,clearly increase from class Cl to class C4. The hyperhaline waters include different subtypes of the major brine type"c",, of EUGSTER & HARDIE (1978), the Na+ - (Mg2+) - Cl- - (SO42-) being the most frequent. Nutrient concentrations fall within a wide range (N.NO3 from 0.1 to 1100 mg-at 1-1; PRT from 0.01 to 23.56 mg-at l-1 and Si from 1.0 to 502.0 mg-at l-1). The oxygen values are very variable too, ranging between 0 and 14.4 ml l-1. Four different patterns of nutrient distribution have been distinguished based on the mean concentrations of N.NO3-, and TRP (mean values in mg-at l-1): A, N.NO3- l ; B, N.NO3- > 100, TRP < 1; C, 10 < N.NO3- < 100, TRP < 1; C, D, N.NO3- < 10, TRP < 1. As a rule, lagoons of low salinity (C1 and C2 classes) display the nutrient pattern C, and lagoons of high salinity (C3 and C4) show the nutrient pattern D. Model A only appears in waters of very low salinity, whereas model B does not seem to be related to salinity

Chemical composition of the small coastal lagoons of the Mediterranean Spanish littoral

About sixty small water bodies (coastal lagoons, marshes, salt pans, channels, springs, etc.) of the Spanish Mediterranean coast were sampled seasonally for one year (1979-1980), in order to study different aspects of their chemical composition. The concentrations of major ions (alkalinity, Cl-, Ca2+, Mg2+, Na+, and K+), nutrients (N.NO-3, N.NO2-, TRP and Si), oxygen and pH were determined for this purpose. The salt concentrations measured range between 0.4 and 361.3 g l-1. The samples have been divided into four classes of salinity (in g l-1): Cl, S 40. Within these classes, the pattern of ionic dominance recorded is remarkably constant and similar to that found in most coastal lagoons (Cl- > So42- > Alk., for the anions, and Na+ > Mg2+ > Ca2+ > K+, for the cations), although other models occur especially in the first class. The dominance of Na+ and Cl-, as well as the molar ratios Mg2+/Ca2+ and Cl- / SO42- ,clearly increase from class Cl to class C4. The hyperhaline waters include different subtypes of the major brine type"c",, of EUGSTER & HARDIE (1978), the Na+ - (Mg2+) - Cl- - (SO42-) being the most frequent. Nutrient concentrations fall within a wide range (N.NO3 from 0.1 to 1100 mg-at 1-1; PRT from 0.01 to 23.56 mg-at l-1 and Si from 1.0 to 502.0 mg-at l-1). The oxygen values are very variable too, ranging between 0 and 14.4 ml l-1. Four different patterns of nutrient distribution have been distinguished based on the mean concentrations of N.NO3-, and TRP (mean values in mg-at l-1): A, N.NO3- l ; B, N.NO3- > 100, TRP < 1; C, 10 < N.NO3- < 100, TRP < 1; C, D, N.NO3- < 10, TRP < 1. As a rule, lagoons of low salinity (C1 and C2 classes) display the nutrient pattern C, and lagoons of high salinity (C3 and C4) show the nutrient pattern D. Model A only appears in waters of very low salinity, whereas model B does not seem to be related to salinity

Redaccio col·laborativa de treballs en la docència de les ciències experimentals. Comparació entre mètodes tradicionals i wikis

En aquest treball es presenta la recerca en docència que desenvolupen els autors, ique fa referència a l"ús de la redacció col·laborativa de documents i treballscooperatius en docència. Aquesta recerca es dedica principalment a l"anàlisi de l"ús de metodologies TIC, com és el wiki, per tal d"avaluar-ne els seus avantatges i inconvenients respecte als mètodes tradicionals de treball col·laboratiu. Entre d"altres aspectes, ens interessen la mesura de l"esforç en temps de dedicació de l"alumnat i també del professorat, i la possibilitat de fer una avaluació de cada alumne que inclogui la seva contribució individual al treball de grup. L"estudi s"està fent en diverses assignatures dels ensenyaments de Biologia, Ciències Ambientals i Infermeria. Es presenten algunes dades sobre els resultats obtinguts en aspectes com ara les dificultats tècniques, qüestions organitzatives i grau de satisfacció dels alumnes. S"aporten algunes dades preliminars sobre la valoració diferent de cada alumne segons el mètode