177 research outputs found
Habitat and scale shape the demographic fate of the keystone sea urchin <i>Paracentrotus lividus</i> in Mediterranean macrophyte communities
Demographic processes exert different degrees of control as individuals grow, and in species that span several habitats and spatial scales, this can influence our ability to predict their population at a particular life-history stage given the previous life stage. In particular, when keystone species are involved, this relative coupling between demographic stages can have significant implications for the functioning of ecosystems. We examined benthic and pelagic abundances of the sea urchin Paracentrotus lividus in order to: 1) understand the main life-history bottlenecks by observing the degree of coupling between demographic stages; and 2) explore the processes driving these linkages. P. lividus is the dominant invertebrate herbivore in the Mediterranean Sea, and has been repeatedly observed to overgraze shallow beds of the seagrass Posidonia oceanica and rocky macroalgal communities. We used a hierarchical sampling design at different spatial scales (100 s, 10 s and <1 km) and habitats (seagrass and rocky macroalgae) to describe the spatial patterns in the abundance of different demographic stages (larvae, settlers, recruits and adults). Our results indicate that large-scale factors (potentially currents, nutrients, temperature, etc.) determine larval availability and settlement in the pelagic stages of urchin life history. In rocky macroalgal habitats, benthic processes (like predation) acting at large or medium scales drive adult abundances. In contrast, adult numbers in seagrass meadows are most likely influenced by factors like local migration (from adjoining rocky habitats) functioning at much smaller scales. The complexity of spatial and habitat-dependent processes shaping urchin populations demands a multiplicity of approaches when addressing habitat conservation actions, yet such actions are currently mostly aimed at managing predation processes and fish numbers. We argue that a more holistic ecosystem management also needs to incorporate the landscape and habitat-quality level processes (eutrophication, fragmentation, etc.) that together regulate the populations of this keystone herbivore
Estudio de la función de consumo familiar en la economía española
Este trabajo trata sobre el comportamiento del consumo familiar en España y las variables que lo determinan. Primero hemos estudiado las diferentes teorías propuestas por algunos de los economistas más importantes: el consumo intertemporal de Fisher, la función de consumo keynesiana, la teoría del ciclo vital y la de la renta permanente. En segundo lugar, se ha realizado un estudio empírico con datos de la economía española para determinar el grado de relación entre el consumo y sus variables explicativas. Se han tomado datos desde el primer trimestre de 1991 hasta el primero de 2016. Tras analizar que las variables son no estacionarias y que por lo tanto pueden estar cointegradas, no se ha encontrado ninguna relación de cointegración a largo plazo entre ellas, de manera que se ha procedido a estimar una serie de modelos en primeras diferencias y con retardos para analizar los efectos a corto plazo entre distintos subconjuntos de nuestras variables. El modelo finalmente seleccionado nos muestra una débil relación de los retardos de la renta disponible y de la riqueza de las familias sobre el consumo, aunque su capacidad predictiva es buena, ya que comete un bajo porcentaje de error
Microwave imaging technology for in-line food contamination monitoring
Foreign body contamination in food is one of the major sources of complaints against food manufacturers, and it can lead to injury, loss of brand loyalty and large recall expenses. Different technologies, such as X-ray or infrared techniques, are currently applied to detection systems used for food inspection, but physical contamination, with e.g. wood, plastic, metal and glass fragments, is still present in food. For this reason, there is the interest to develop new technologies able to address the still unmet needs of food industry. In this paper, we report about preliminary investigations of the use of the microwave imaging technology for food contamination monitoring. Numerical results show the feasibility of the proposed approach. The realization of prototype measurement system is under development
The effect of a centenary storm on the long-lived seagrass Posidonia oceanica
We used the disturbance resulting from a once in a 100‐yr storm on the northwest Mediterranean coast to examine the extent of the disturbance, the tolerance thresholds to burial, and the medium‐term response of the long‐lived Posidonia oceanica seagrass. Sediment burial at 12 surveyed areas was particularly strong in shallow meadows, with 23% of their surfaces buried, on average, under more than 10 cm of sediment. In contrast, less than 5% of the meadow was affected at deeper locations. At three sites, we tracked short‐term mortality along a gradient of sediment burial. Survival response to burial was clearly nonlinear, with a significant threshold at 4-5 cm, beyond which shoot mortality was 100%. To track medium‐term potential recovery, we established permanent plots subject to three sediment burial levels (0-5, 5-10, and > 10 cm burial) in four meadows. Where the initial shoot mortality was 100%, we recorded no shoot recovery over the 4‐yr period. In the remaining plots, where some shoots remained alive, we detected either further mortality or shoot recovery of 7% per year on average. Extreme storm events can result in sudden catastrophic losses of seagrass cover in shallow P. oceanica meadows. In the long term and due to the long return time of such storms, the species may still be able to recover despite its low recovery potential. However, added anthropogenic stressors, including climate change, may seriously test the ability of long‐lived shallow seagrass ecosystems to resist high‐intensity natural disturbances and may be critical for its persistence
Detecting the impacts of harbour construction on a seagrass habitat and its subsequent recovery
Managing coastal development requires a set of tools to adequately detect ecosystem and water column degradation, but it also demands tools to detect any post-disturbance improvement. Structural seagrass indicators (such as shoot density or cover) are often used to detect or assess disturbances, but while they may be very sensitive to the impact itself, it is unclear if those indicators on their own can effectively reflect recovery at time scales relevant to managers. We used the construction of a harbour affecting a nearby Posidonia oceanica seagrass community to test the ability of a set of indicators (structural and others) to detect alterations and to evaluate their sensitivity to recovery of environmental quality after harbour construction was complete and the disturbance ceased. We used a Beyond Before After Control Impact (BBACI) design to evaluate effects on one impacted and three control meadows where we used structural, morphological, community and physiological indicators (26 in total) to asses disturbance impacts. Additionally, we measured some of the potential environmental factors that could be altered during and after the construction of the harbour and are critical to the survival of the seagrass meadow (light, sediment organic matter, sediment accrual). Harbour construction caused a clear increase in sediment organic matter and in sediment deposition rates, especially fine sand. Light availability was also reduced due to suspended sediments. Sediment and light conditions returned to normal levels 5 and 15 months after the construction began. As expected, seagrass structural indicators responded unequivocally to these environmental changes, with clear reductions in shoot density. Additionally, reduced light conditions quickly resulted in a decline in carbohydrate content in affected meadows. Unexpectedly, we also recorded a significant increase in metal content in plant tissues. No response was detected in the physiological indicators related to eutrophication (e.g. N and P content in tissues) and in morphological (shoot biomass) and community (epiphyte biomass) indicators. More than three years after the completion of the harbour, structural indicators did not show any sign of recovery. In contrast, physiological indicators, mainly heavy metal and carbohydrates content, were much better in detecting the improvement of the environmental conditions over the fairly short period of this study. These results indicate that while structural indicators are critical to evaluate the immediate effect of disturbances and the recovery on impacted systems, specific physiological indicators may be much better suited to determining the timing of environmental quality recovery. The design of impact and monitoring protocols in the wake of coastal developmental projects need to consider the differential effectiveness and time-response of measured indicators carefully
Study of Cardiac Repolarization during Oral Glucose Tolerance Test in Metabolic Syndrome Patients
Abstract QT interval could be relevant for cardiopathy assessment in metabolic syndrome (MS
Science Education at High School: a VISIR Remote Lab Implementation
Experimentation is crucial in science teaching at any education level. Students’ motivation and collaborative work are also essential in order to achieve positive learning outcomes. This article portrays the implementation of remote experimentation using VISIR in a Physics subject at high-school level. Qualitative and quantitative data were analyzed for this particular case study in order to shed light on the influence of VISIR on students’ motivation. Results showed that VISIR remote lab is a powerful tool to arouse interest in electronic circuit topics.info:eu-repo/semantics/publishedVersio
Stand Up Científico (Popularización entre risas)
PopER Stand Up Científico es el primer grupo latinoamericano de comedia en vivo de divulgación científica. En el grupo hay actualmente dieciocho integrantes, entre estudiantes, graduados, postgraduados e investigadores científicos, cubriendo una amplia variedad de disciplinas (biología, química, bioquímica, biotecnología, astronomía, paleontología, física, matemática.). El grupo tiene su origen en el primer curso de stand up científico, iniciativa del Ministerio de Ciencia, Tecnología e Innovación Productiva en el año 2015, que a través del Programa de Popularización de la Ciencia y la Innovación, Tecnópolis y TECtv organizó un curso coordinado por Diego Golombek y dictado por Diego Wainstein. Una vez conformado el grupo, desarrollamos nuestros materiales individuales y grupales buscando, a través del stand up, desmitificar la idea del científico serio, de guardapolvos y anteojos, haciendo foco en la vida personal de los “científicos-standuperos” y su relación con su trabajo. A su vez, se busca comunicar ciencia acercando conceptos e ideas científicas de un modo entretenido: queremos enamorar de la ciencia a los que se acercan, despertar curiosidad en los que todavía no la conocen y resonar en aquellos que ya pertenecen a nuestra comunidad. La invitación es a reírse de/con nosotros. El show es apto para todo público y desde el año 2015 de manera continua presentamos nuestro espectáculo en bares, centros culturales, por ejemplo el Centro Cultural de la Ciencia: (C3), Universidades públicas y privadas (UNLP, UBA, UNQUI, UCALP, UDE, etc.), museos (Museo de La Plata, Museo de Ciencias Naturales Bernardino Rivadavia), escuelas (primarias y secundarias), Congresos y festivales, obteniendo una respuesta positiva por parte de los espectadores. El nombre Poper es un juego de palabras con las iniciales de POPularización Entre Risas y un homenaje al epistemólogo Karl Popper
Herbivore control in connected seascapes: habitat determines when population regulation occurs in the life history of a key herbivore
Herbivore outbreaks often trigger catastrophic overgrazing events in marine macrophyte ecosystems. The sea urchin Paracentrotus lividus, the dominant herbivore of shallow Mediterranean seascapes, is capable of precipitating shifts to barrens when its populations explode. Paracentrotus lividus is found ubiquitously in rocky macroalgal communities and in sandy seagrass meadows of Posidonia oceanica, two of the most important subtidal habitats in the Mediterranean. We explored if habitat‐specific regulation across the principal stages of the urchin life cycle could help explain the persistence of these populations in connected mosaics. We measured each of three relevant ecological processes (i.e. settlement, post‐settlement survival and predation) across a wide stretch of the Mediterranean coast (ca 600 km). Our results show that habitat‐specific regulation is critical in determining urchin populations: each habitat limited urchin sub‐populations at different life stages. Settlement was never limiting; urchins settled at similar rates in both habitats across the coast. Post‐settlement survival was a clear bottleneck, particularly in seagrass meadows where no juvenile urchins were recorded. Despite this bottleneck in seagrasses, adult urchin populations were very similar in both seagrass and macroalgal habitats indicating that other processes (potentially migration) could be key in determining adult distributions across the mosaic. The fact that population regulation is clearly habitat‐specific suggests that sea urchin populations may be significantly buffered from bottlenecks in mixed seascapes where both habitats co‐occur. Sea urchin populations can therefore persist across the seascape despite strong habitat‐specific regulation either by maintaining reproductive output in one habitat or by migrating between them. By affording these regulatory escapes to habitat‐modifying species, patchy mosaics may be much more prone to herbivore outbreaks and a host of cascading effects that come in their wake.info:eu-repo/semantics/acceptedVersio
Differences in predator composition alter the direction of structure‐mediated predation risk in macrophyte communities
Structural complexity strongly influences the outcome of predator-prey interactions in benthic marine communities affecting both prey concealment and predator hunting efficacy. How habitat structure interacts with species‐specific differences in predatory style and antipredatory strategies may therefore be critical in determining higher trophic functions. We examined the role of structural complexity in mediating predator-prey interactions across several macrophyte habitats along a gradient of structural complexity in three different bioregions: western Mediterranean Sea (WMS), eastern Indian Ocean (EIO) and northern Gulf of Mexico (NGM). Using sea urchins as model prey, we measured survival rates of small (juveniles) and medium (young adults) size classes in different habitat zones: within the macrophyte habitat, along the edge and in bare sandy spaces. At each site we also measured structural variables and predator abundance. Generalised linear models identified biomass and predatory fish abundance as the main determinants of predation intensity but the efficiency of predation was also influenced by urchin size class. Interestingly though, the direction of structure‐mediated effects on predation risk was markedly different between habitats and bioregions. In WMS and NGM, where predation by roving fish was relatively high, structure served as a critical prey refuge, particularly for juvenile urchins. In contrast, in EIO, where roving fish predation was low, predation was generally higher inside structurally complex environments where sea stars were responsible for much of the predation. Larger prey were generally less affected by predation in all habitats, probably due to the absence of large predators. Overall, our results indicate that, while the structural complexity of habitats is critical in mediating predator-prey interactions, the direction of this mediation is strongly influenced by differences in predator composition. Whether the regional pool of predators is dominated by visual roving species or chemotactic benthic predators may determine if structure dampens or enhances the influence of top-down control in marine macrophyte communities
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