985 resultados para Biotic communities.


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Loss of species will directly change the structure and potentially the dynamics of ecological communities, which in turn may lead to additional species loss (secondary extinctions) due to direct and/or indirect effects (e.g. loss of resources or altered population dynamics). Furthermore, the vulnerability of food webs to repeated species loss is expected to be affected by food web topology, species interactions, as well as the order in which species go extinct. Species traits such as body size, abundance and connectivity might determine a species' vulnerability to extinction and, thus, the order in which species go primarily extinct. Yet, the sequence of primary extinctions, and their effects on the vulnerability of food webs to secondary extinctions, when species abundances are allowed to respond dynamically, has only recently become the focus of attention. Here, we analyse and compare topological and dynamical robustness to secondary extinctions of model food webs, in the face of 34 extinction sequences based on species traits. Although secondary extinctions are frequent in the dynamical approach and rare in the topological approach, topological and dynamical robustness tends to be correlated for many bottom-up directed, but not for top-down directed deletion sequences. Furthermore, removing species based on traits that are strongly positively correlated to the trophic position of species (such as large body size, low abundance, high net effect) is, under the dynamical approach, found to be as destructive as removing primary producers. Such top-down oriented removal of species are often considered to correspond to realistic extinction scenarios, but earlier studies, based on topological approaches, have found such extinction sequences to have only moderate effects on the remaining community. Thus, our result suggests that the structure of ecological communities, and therefore the integrity of important ecosystem processes could be more vulnerable to realistic extinction sequences than previously believed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Using the contingent valuation method, this study investigates the preferences of local people for a wind farm that is planned in the Province of Rome. We estimate the reductions in their bimonthly electrical bills over a period of time that respondents are willing to accept as compensation for the installation of the wind farm. Our results suggest that respondents who perceive that the wind farm generates substantial negative impacts on landscape beauty ask higher reductions than others, while respondents who believe that the wind farm produces economic benefits for local communities ask lower reductions than others. Finally, we find that the demand for compensative measures is influenced particularly by socio-economic factors such as age and education.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Under-boulder communities are listed as a priority habitat as they provide shelter, shade and moisture and play an important role in the life-cycle of many marine algae and animals.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper investigates the profile of teachers in the island of Ireland who declared themselves willing to undertake professional development activities in programming, in particular to master programming by taking on-line courses involving the design of computer games. Using the Technology Acceptance Model (TAM), it compares scores for teachers “willing” to undertake the courses with scores for those who declined, and examines other differences between the groups of respondents. Findings reflect the perceived difficulties of programming and the current low status accorded to the subject in Ireland. The paper also reviews the use of games-based learning as a “hook” to engage learners in programming and discusses the role of gamification as a tool for motivating learners in an on-line course. The on-line course focusing on games design was met with enthusiasm, and there was general consensus that gamification was appropriate for motivating learners in structured courses such as those provided.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The bacterial community composition and biomass abundance from a depositional mud belt in the western Irish Sea and regional sands were investigated by phospholipid ester-linked fatty acid profiling, denaturing gradient gel electrophoresis and barcoded pyrosequencing of 16S rRNA genes. The study area varied by water depth (12-111 m), organic carbon content (0.09-1.57% TOC), grain size, hydrographic regime (well-mixed vs. stratified), and water column phytodetrital input (represented by algal polyunsaturated PLFA). The relative abundance of bacterial-derived PLFA (sum of methyl-branched, cyclopropyl and odd-carbon number PLFA) was positively correlated with fine-grained sediment, and was highest in the depositional mud belt. A strong association between bacterial biomass and eukaryote primary production was suggested based on observed positive correlations with total nitrogen and algal polyunsaturated fatty acids. In addition, 16S rRNA genes affiliated to the classes Clostridia and Flavobacteria represented a major proportion of total 16S rRNA gene sequences. This suggests that benthic bacterial communities are also important degraders of phytodetrital organic matter and closely coupled to water column productivity in the western Irish Sea.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Neighborhoods across the globe are becoming increasingly ‘divers’, yet we still find their urban encounters reproduced through negotiating differences that escalates moods of social inequality and spatial imbalances. Research on ethnic division also stresses the spatial aspects of their production as shared urban spaces are mostly signified in the literature as ethnic ‘enclaves’. Territoriality and place attachment, in this sense, has a wide impact on the people’s everyday encounters while experiencing segregation. These historical narratives have produced communities that exhibit high levels of intracommunity relations and localized networking. This article investigates how youngster generations in Northern Ireland perceive, accept and respond to their differences, or perhaps how they act against it, to push the boundaries towards more diversity. In fact, the spatial and temporal encounters that occur among one community and the ‘Other’ signify a sort of negotiations and being more constructive about the future. The argument maintains that territoriality and place attachment has a wide impact on the young people’s everyday experiences. The empirical study shows how individuals and community groups position and identify themselves under the impact of social segregation. Building on social identity theories, I explain how people in Derry have established their own sense of belonging, of who they are, based on their group memberships which eventually became an important source of pride and self-esteem.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Evidence correlates physical activity, psychological restoration, and social health to proximity to parks and sites of recreation. The purpose of this study was to identify perceived constraints to park use in low-income communities facing significant health disparities, with access to underutilized parks. We used a series of focus groups with families, teens, and older adults in neighborhoods with similar demographic distribution and access to parks over 125 acres in size. Constraints to park use varied across age groups as well as across social ecological levels, with perceived constraints to individuals, user groups, communities, and society. Policies and interventions aimed at increasing park use must specifically address barriers across social ecological levels to be successful.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

There is widespread acceptance that clinical educators should be trained to teach, but faculty development for clinicians is undermined by poor attendance and inadequate learning transfer. As a result there has been growing interest in situating teacher development initiatives in clinical workplaces. The relationship between becoming a teacher and clinical workplace contexts is under theorised. In response, this qualitative research set out to explore how clinicians become teachers in relation to clinical communities and institutions. Using communities of practice (CoP) as a conceptual framework this research employed the sensitising concepts of regimes of competence and vertical (managerial) and horizontal (professional) planes of accountability to elucidate structural influences on teacher development. Fourteen hospital physicians completed developmental timelines and underwent semi-structured interviews, exploring their development as teachers. Despite having very different developmental pathways, participants’ descriptions of their teacher identities and practice that were remarkably congruent. Two types of CoP occupied the horizontal plane of accountability i.e. clinical teams (Firms) and communities of junior doctors (Fraternities). Participants reproduced teacher identities and practice that were congruent with CoPs’ regimes of competence in order to gain recognition and legitimacy. Participants also constructed their teacher identities in relation to institutions in the vertical plane of accountability (i.e. hospitals and medical schools). Institutions that valued teaching supported the development of teacher identities along institutionally defined lines. Where teaching was less valued, clinicians adapted their teacher identities and practices to suit institutional norms. Becoming a clinical educator entails continually negotiating one’s identity and practice between two potentially conflicting planes of accountability. Clinical CoPs are largely conservative and reproductive of teaching practice whereas accountability to institutions is potentially disruptive of teacher identity and practice.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Neste trabalho foi efectuada uma avaliação integrada usando descritores sedimentares e biológicos ao nível da espécie e da comunidade e índices bióticos de síntese para o traçamento do enriquecimento orgânico numa região, com características dispersivas, da costa Oeste de Portugal. Na área estudada existem gradientes ambientais e biológicos relacionados com a heterogeneidade da paisagem sedimentar, a qual inclui sedimentos desde areias finas limpas a vasas. Contudo, na área próxima do emissário, esta paisagem é mais homogénea e constituída por areia fina com baixo teor em finos. Nesta região, alguns dos descritores estudados deram uma indicação coerente de alterações ambientais associadas ao enriquecimento orgânico. O potencial de oxidação - redução mostrou valores negativos até 250 m do emissário, o que indicia que a degradação da matéria orgânica que entra no sistema cria condições reduzidas no sedimento. Os isótopos estáveis de carbono e azoto no sedimento diferenciam a área mais próxima do emissário, que apresenta uma depleção de acordo com uma origem terrestre da matéria orgânica naquela parte da plataforma. Uma imagem similar foi obtida pela análise dos isótopos estáveis na macrofauna que diagnosticou a origem terrestre da matéria orgânica consumida. A composição específica e a abundância das comunidades bentónicas também são significativamente diferentes junto ao emissário, onde são dominadas por espécies oportunistas, tolerantes ao enriquecimento orgânico. No entanto, os índices bióticos em validação no âmbito da implementação da Directiva Quadro da Água, não foram eficientes a mostrar as alterações bentónicas associadas ao enriquecimento orgânico apesar de alguns índices se basearem nos limiares de tolerância/sensibilidade a este tipo de perturbação. Apesar deste caso de estudo reflectir um enriquecimento orgânico moderado, uma vez que não foram detectadas alterações sedimentares ou acumulação de matéria orgânica, nem um significativo empobrecimento das comunidades biológicas junto ao emissário, a análise ao nível dos índices bióticos de síntese pode levar à perda de informação essencial e, portanto, prejudicar a nossa capacidade de diagnóstico devendo ser usados com cuidado. A análise do conjunto de dados da composição específica forneceu uma imagem mais precisa da perturbação ambiental e descritores específicos, tais como os isótopos estáveis, permitiram uma melhor compreensão da extensão espacial do enriquecimento orgânico.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Os ecossistemas de água doce – responsáveis por funções ambientais importantes e pelo fornecimento de bens e serviços insubstituíveis – têm vindo a ser severamente afectados por perturbações antropogénicas. A conversão de floresta em terreno agrícola afecta os sistemas aquáticos através de uma série de mecanismos: sedimentação; excesso de nutrientes; contaminação; alterações hidrológicas; e remoção de vegetação ripícola. As comunidades de macroinvertebrados de água doce – devido à sua diversidade, ubiquidade e sensibilidade às perturbações ambientais – revelam-se como particularmente adequadas para estudos de avaliação da integridade ecológica destes sistemas expostos simultaneamente a múltiplos factores de impacto. O uso sistemático de respostas biológicas para avaliação de mudanças ambientais – ou biomonitorização – pode ser levado a cabo através de diversas metodologias, que, de uma forma geral, não consideram aspectos funcionais das comunidades biológicas e têm aplicabilidade geograficamente restrita. A biomonitorização através de atributos biológicos (características que reflectem a adaptação das espécies ao seu meio ambiente) revela-se como uma ferramenta promissora na resolução dos problemas referidos, apresentando vantagens adicionais: relações causa-efeito directas; melhoria na diferenciação de impactos; e integração da variabilidade natural. O presente estudo apresenta uma revisão critica do estado-da-arte actual na área do uso de atributos biológicos em biomonitorização. Até à data de publicação, não estava disponível nenhum outro trabalho com a base conceptual do uso de atributos de macroinvertebrados enquanto descritores de comunidades e para efeitos de biomonitorização e gestão de sistemas de água doce. Descrevem-se as teorias ecológicas de suporte destas metodologias (conceitos de habitat-molde e de filtros paisagísticos) e os estudos que aplicaram estas teorias em cenários reais, tendo-se chamado a atenção para questões técnicas e possíveis soluções. As necessidades futuras nesta área englobam: o desenvolvimento de uma só ferramenta de biomonitorização de aplicação alargada; uma maior compreensão da variabilidade natural nas comunidades biológicas; diminuição dos efeitos de soluções de compromisso biológico e sindromas; realização de estudos autoecológicos adicionais; e detecção de impactos específicos em cenários de impacto complexos. Um dos objectivos deste estudo foi contribuir para a melhoria das técnicas de biomonitorização através de atributos, focalizando em comunidades de macroinvertebrados ribeirinhas em diferentes regiões biogeográficas (as bacias hidrográficas dos rios: Little e Salmon em New Brunswick, Canadá; Anllóns na Galiza, Espanha; Reventazón em Cartago, Costa Rica). Em cada região, foram estudados gradientes de uso agrícola de solo, incluindo desde bacias hidrográficas quase exclusivamente cobertas por floresta até bacias sob a influência maioritária de actividades agrícolas intensivas. Em cada gradiente de uso de solo, a caracterização da comunidade biológica (por amostragem de macroinvertebrados em troços de rápidos) foi acompanhada pela caracterização do habitat circundante (incluindo propriedades da bacia hidrográfica, análise química das águas e outras propriedades à escala local). A comunidade de macroinvertebrados foi caracterizada através de informação taxonómica, métricas estruturais, índices de diversidade, métricas de tolerância, índices bióticos e através da compilação de atributos biológicos e fisiológicos gerais, de história de vida e de resistência a perturbações. Análises estatísticas univariadas e multivariadas foram usadas para evidenciar os gradientes biológicos e físico-químicos, confirmar a sua co-variação, testar a significância da discriminação de níveis de impacto e estabelecer comparações inter-regionais. A estrutura de comunidades revelou os complexos gradientes de impacto, que por sua vez co-variaram significativamente com os gradientes de uso de solo. Os gradientes de impacto relacionaram-se sobretudo com entrada de nutrientes e sedimentação. Os gradientes biológicos definidos pelas medidas estruturais seleccionadas co-variaram com os gradientes de impacto estudados, muito embora apenas algumas variáveis estruturais tenham individualmente discriminado as categorias de uso de solo definidas a priori. Não foi detectada consistência nas respostas das medidas estruturais entre regiões biogeográficas, tendo-se confirmadado que as interpretações puramente taxonómicas de impactos são difíceis de extrapolar entre regiões. Os gradientes biológicos definidos através dos atributos seleccionados também co-variaram com os gradientes de perturbação, tendo sido possível obter uma melhor discriminação de categorias de uso de solo. Nas diferentes regiões, a discriminação de locais mais impactados foi feita com base num conjunto similar de atributos, que inclui tamanho, voltinismo, técnicas reproductivas, microhabitat, preferências de corrente e substrato, hábitos alimentares e formas de resistência. Este conjunto poderá vir a ser usado para avaliar de forma predictiva os efeitos das modificações severas de uso de solo impostas pela actividade agrícola. Quando analisadas simultaneamente através dos atributos, as comunidades das três regiões permitiram uma moderada mas significativa discriminação de níveis de impacto. Estas análises corroboram as evidências de que as mudanças nas comunidades de macroinvertebrados aquáticos em locais sob a influência de agricultura intensiva podem seguir uma trajectória convergente no espaço multidimensional, independentemente de factores geográficos. Foram fornecidas pistas para a identificação de parâmetros específicos que deverão ser tidos em conta no planeamento de novos programas de biomonitorização com comunidades de macroinvertebrados bentónicos, para aplicação numa gestão fluvial verdadeiramente ecológica, nestas e noutras regiões. Foram ainda sugeridas possíveis linhas futuras de investigação.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Estuaries are poles of attraction for human settlement which is a source of pressures to surface water bodies. The implementation of the European Water Framework Directive (WDF, 2000/60/EC) has increased the investigation in order to develop methodologies to assess the Ecological Quality Status (EQS) of aquatic ecosystems. Transitional systems are naturally stressed and characterized by highly dynamic physical, chemical and hydro-morphologic conditions and by species with a higher level of tolerance to change, being more difficult to develop suitable quality indicators for these systems. The general purpose of this study is to test the ability of synthesis descriptors, including primary (S, taxa richness) and derived biological variable (H’, Shannon-Wiener diversity), biotic indices (AMBI and M-AMBI), body size properties (abundance distribution by body size classes, length, weight and length-weight relationships) and non-taxonomic indices (ISS), as well as functional indicators related to the decomposition rates of various experimental substrates, a macrophyte (Phragmites australis) and an alga (Fucus vesiculosus), to evaluate the environmental quality in transitional systems. This study was carried out in one of the most pristine channels of the Ria the Aveiro, Mira Channel, along a full salinity gradient and in a metals and metalloid sediment contamination area, the Estarreja Channel, and two reference channels (Canelas and Salreu). In this study were used different sampling techniques, the leaf-bag technique and a hand-held corer. In Mira Channel, the alga and the macrophyte presented an opposite trend in the decomposition rate along the salinity gradient, with the decomposition rates of the alga always higher than those of the macrophyte. The decomposition rates of the macrophyte and the alga were higher in the mid estuary and in higher salinity areas, respectively, corresponding to the preferencial distribution areas of each species. The macrobenthic fauna associated with the decaying and an artificial substrate (control) showed equally well the benthic succession from the marine to the freshwater areas and, despite the strong differences in the decay rates, no significant differences were found between the benthic communities associated with the alga and the macrophyte. The body size properties of the macrobenthic fauna associated with the P. australis leaf-bag (1mm and 5mm) and corer samples were studied along the full salinity gradient. The dominant species of the sub-set of measured specimens were not the same of the original macrobenthic fauna sampled but, despite that, the sub-set of measured specimens was also able to show the benthic succession from the marine to the freshwater areas. The body size abundance distribution of the benthic macroinvertebrates according to the ISS size classes did not show a particular trend in any sampler along the salinity gradient. Significant differences were found in the length, weight and length-weight relationships of Annelids, , Molluscs and even some species along the salinity gradient. No significant differences were found in the AMBI, M-AMBI and ISS values along the salinity gradient for all the samplers. The EQS of the corer samples obtained using the M-AMBI was lower than that of the leaf-bags. The EQS obtained with the ISS was higher than that obtained with the M-AMBI in the leaf-bags but not in the corer samples. The ecological effects of contaminated sediments associated with the industrial chemical effluents discharged in the Estarreja Channel were studied a decade after ceasing the emissions, using the Sediment Quality Triad approach and two reference channels. The results showed that despite the emissions ceased in 2004, the sediment remains polluted with high levels of metals and metalloid, available to bioaccumulation and with severe consequences at the community level. The sediment contamination problem was also studied using the leaf-bag technique with a macrophyte, an alga and a control substrate. The results showed that the decay rates, the associated macrofauna and the application of the AMBI, M-AMBI and ISS indices to the mesh-bag samples were not able to identify the sediment contamination. Contrarily to the AMBI, the M-AMBI and the ISS showed significant differences between the contaminated and the reference channels for the corer samples. Although such statistical significance, the interest of using these complex biotic indices could be questioned, when much simple ones, like the S and H’ allow to reach the same conclusions.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Introduction: The objectives of this study were to examine relationships between neighbourhood-level and individual-level characteristics and physical activity in deprived London neighbourhoods. Methods: In 40 of the most deprived neighbourhoods in London (ranked in top 11% in London by Index of Multiple Deprivation) a cross-sectional survey (n = 4107 adults aged > = 16 years), neighbourhood audit tool, GIS measures and routine data measured neighbourhood and individual-level characteristics. The binary outcome was meeting the minimum recommended (CMO, UK) 5×30 mins moderate physical activity per week. Multilevel modelling was used to examine associations between physical activity and individual and neighbourhood-level characteristics. Results: Respondents living more than 300 m away from accessible greenspace had lower odds of achieving recommended physical activity levels than those who lived within 300 m; from 301–600 m (OR = 0.7; 95% CI 0.5–0.9) and from 601–900 m (OR = 0.6; 95% CI 0.4–0.8). There was substantial residual between-neighbourhood variance in physical activity (median odds ratio = 1.7). Other objectively measured neighbourhood-level characteristics were not associated with physical activity levels. Conclusions Distance to nearest greenspace is associated with meeting recommended physical activity levels in deprived London neighbourhoods. Despite residual variance in physical activity levels between neighbourhoods, we found little evidence for the influence of other measured neighbourhood-level characteristics.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Introduction The objectives of this study were to examine relationships between neighbourhood-level and individual-level characteristics and physical activity in deprived London neighbourhoods. Methods In 40 of the most deprived neighbourhoods in London (ranked in top 11% in London by Index of Multiple Deprivation) a cross-sectional survey (n = 4107 adults aged > = 16 years), neighbourhood audit tool, GIS measures and routine data measured neighbourhood and individual-level characteristics. The binary outcome was meeting the minimum recommended (CMO, UK) 5×30 mins moderate physical activity per week. Multilevel modelling was used to examine associations between physical activity and individual and neighbourhood-level characteristics. Results Respondents living more than 300 m away from accessible greenspace had lower odds of achieving recommended physical activity levels than those who lived within 300 m; from 301–600 m (OR = 0.7; 95% CI 0.5–0.9) and from 601–900 m (OR = 0.6; 95% CI 0.4–0.8). There was substantial residual between-neighbourhood variance in physical activity (median odds ratio = 1.7). Other objectively measured neighbourhood-level characteristics were not associated with physical activity levels. Conclusions Distance to nearest greenspace is associated with meeting recommended physical activity levels in deprived London neighbourhoods. Despite residual variance in physical activity levels between neighbourhoods, we found little evidence for the influence of other measured neighbourhood-level characteristics.