331,600 research outputs found
Spatial variation of reef fishes and the relative influence of biotic and abiotic habitat traits
No full textPatterns of distribution of reef fishes were examined across three spatial scales and related to habitat traits along
25 km of the northern Portuguese coast. Response variables included the multivariate assemblage structure, the total
number of taxa and individuals, and the abundance of single groups categorized according to their preference for
the benthic, proximo-benthic or pelagic environment, feeding and reproductive behaviour. Habitat traits included
topographic elements (small and large ‘drops’ like cracks and crevices) and the extent of dominant morpho-functional
types of macroalgae (kelp, large foliose, small erect, turf-forming filamentous, and encrusting). All fish responses were
characterized by the largest variance at the smallest scale (among transects tens m apart), followed by that among
reefs (hundreds m to 1 km apart) and almost null variance among sites (some km apart). Small and large ‘drops’ of
the substratum explained, respectively, considerable variation of assemblage structure and the total abundance of
individuals, while the extent of bare rock influenced the richness of taxa and that of benthic fishes, fishes feeding on
sessile invertebrates and fishes laying benthic eggs or having nesting behaviour. Combinations of abiotic and biotic
structural attributes of reefs influenced proximo-benthic fishes, the predators of mobile animals and fishes releasing
pelagic eggs. The here reported associations between patterns of distribution of reef fishes and habitat traits have
implications for the design of future protection schemes suitable to guarantee the conservation of reef fish communities
and of the processes responsible for their variation. Within the SLOSS (single-large vs. several-small) debate in the
design of marine reserves, for example, effective protection to the studied reef fishes would be provided by a set of
small reserves, rather than a single large which might be appropriate for fishes having wider home ranges
Potential effects of kelp species on local fisheries
No full text1. Kelp species are ecosystem engineers in temperate coasts, where they provide valuable services
to humans. Evidence of the declines of kelp forests exists from several regions, but their
effects on fisheries still need to be elucidated. More effective management strategies for sustainable
fisheries require a synthesis of research findings and an assessment of how research
could be improved to fill current gaps.
2. This review aimed to: (i) summarize the available evidence on the influence of changes in
kelp density and/or area on the abundance and diversity of associated fisheries and (ii) examine
how research on kelp–fisheries interactions could better support effective management.
3. Most studies (67%) reported data ascribable, directly or indirectly, to a positive relationship
between kelp and fishery-relevant variables, 11% provided evidence of a negative relationship,
15% indicated species-specific findings and the remaining found unclear or ‘neutral’
relationships.
4. Important shortcomings were identified, including the paucity of experimental studies suitable
to test for unequivocal cause–effect relationships, the disproportion between North America,
which is well-studied, and other regions and between the large number of fish-based
investigations and the small number of those focusing on other commercially important organisms,
and the general lack of studies carried out over spatial and temporal scales comparable to
those of global processes driving patterns of distribution of both kelps and fisheries.
5. Synthesis and applications. The consistency of most studies in showing a positive kelp–fishery
relationship supports the protection of kelp habitats stated by current environmental
directives. However, achieving their goals requires that the limitations we detect are
addressed through better connections between research, management practice and policy.
This would require the following: (i) researchers to combine multiple approaches (large-scale
experimental studies and modelling) for the analysis of kelp–fisheries relationships; (ii) funding
agencies to provide resources needed to fill the existing gaps; and (iii) researchers and
institutions from less studied regions to strengthen collaborations with those from regions
where there have been more investigations into kelp–fishery systems. This is essential under
present and predicted environmental changes, with the ultimate aim of conserving and allowing
the sustainable use of critically important habitats and of fishery resources relying on
these
O trágico na poética de Cruz e Sousa
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Literatura, Florianópolis, 2014.Este trabalho elabora uma leitura que destaca uma emergência trágica nos textos poéticos de João da Cruz e Sousa (1861?1898). Na linhagem de Nestor Vítor, a crítica do poeta utiliza reiteradamente o significante "tragédia" - na acepção do senso comum -, normalmente adjetivando sua vida. Deixando ressoar esse vocábulo e apoiando-se nas imagens que os poemas evocam, esta pesquisa opera um deslocamento de sentido no significante "trágico" e o utiliza enquanto gênero que adjetiva, não mais a vida, mas os textos de Cruz e Sousa. Para tanto, optou-se por realizar uma comparação capaz de colocar em confronto temporalidades distintas; um contraponto com as estéticas surrealista, romântica e barroca. Foram percebidos contatos relevantes com os textos cruzesousianos tanto na imagem do Ângelus, de Millet, e na leitura surrealista que Salvador Dalí fez da obra, quanto no uso reiterado do mito cristão e sua aparição em outras modalidades artísticas ? como na ópera de Parsifal, ou ainda, no drama trágico alemão e no estudo que fez dele Walter Benjamin. A afinidade reside na tônica dada ao sacrifício, à morte, ao rito religioso. E, a partir daí, se desenha uma hipótese de leitura que faz dessa emergência trágica um modo de conceber a história. Precisamente essa forma de pensar é que caracteriza o decadentismo do fim do século XIX como um momento no qual se privilegiou a reencenação do rito, adotando uma postura crítica ao mito
Type and timing of disturbance modify trajectories of recovery of rockpool assemblages at Aguda (NW Portugal)
No full textPatterns of recovery of rock pool assemblages were experimentally investigated along the rocky shore of Praia da Aguda (NW Portugal). The temporal variance in the structure of whole assemblages and abundance of individual algal and invertebrate organisms was examined after two experimental disturbances differing in intensity, i.e. one able to eliminate all the biota from the substratum, the other able to create a mosaic of bare patches interspersed within the remaining organisms. Two experimental trials were carried out (starting in March 2007 and July 2007, respectively), with a duration of the study of 13 months each. Multivariate results indicated a temporally consistent positive relationship between the intensity of disturbance applied and the temporal variance of the structure of assemblages. A similar response was documented at the univariate level by the encrusting coralline alga Lithophyllum incrustans and the foliose green algae of the genus Ulva, while both experimental disturbances decreased temporal fluctuations of the abundance of mussels. Mytilus galloprovincialis, compared to unmanipulated control. The present study has implications for understanding and predicting responses of intertidal assemblages to natural disturbances whose intensity is predicted to increase in the future, including climate events
Urban vs. extra-urban environments: scales of variation of benthic assemblages in north Portugal
No full textLittoral areas are subject to severe and increasing pressures resulting from human activities occurring along or next to the coast. In this study, patterns of variability in the structure of rocky intertidal benthic assemblages and in the abundance of individual taxa were compared between locations close to the coastal cities of Porto and Vila Nova de Gala (north Portugal) and reference locations far from it in much less urbanized conditions over a temporal scale of fourteen months and multiple spatial scales. Present findings indicated that assemblages were more heterogeneously distributed in the urban than in the extra-urban condition. The total number of taxa and several individual taxa displayed, in general, this same pattern of variability. This could be interpreted as the beginning of a habitat deterioration process with largely unpredictable consequences. The adopted sampling design supports the need for simultaneously including a range of temporal and spatial scales when evaluating responses of coastal marine biodiversity to anthropogenic disturbances
Interplay of experimental harvesting and climate-related disturbance on benthic assemblages of rocky seashores
No full textAssessing responses of assemblages to compounded perturbations is a crucial goal of research on ecological impacts of current and predicted environmental changes. We examined the interactive effects of changes in temporal variance of 'storm-like' mechanical disturbance and in harvesting intensity of mussels (Mytilus galloprovincialis) on sessile assemblages associated with mussel beds on rocky shores in north Portugal. Response variables were measures of temporal variance in the abundance of individual taxa and in the structure of assemblages. Events of disturbance regularly distributed over the period of the experiment determined a lower temporal heterogeneity in assemblage structure than events characterized by larger temporal variance, but only in the presence of an intact mussel bed. The opposite pattern was documented in plots where mussels were completely removed. Univariate results indicated taxon-specific responses, with macroalgae, such as Corallina spp. and Porphyra linearis, showing patterns analogous to the multivariate one and grazing invertebrates displaying an opposite trend. This is one of the first manipulative examples aimed at examining effects of temporal variability of climate-related disturbance on systems increasingly depleted by concomitant stressors. The main finding was that effects of temporal variability of climate-related events of mechanical disturbance are mediated by the presence of intact stands of a foundation species. This may contribute to understanding and predicting responses of populations and assemblages under scenarios of concomitant climatic and non climatic changes
Plec : informatiu d'EINA. Núm. 30
No full textNúm. 30 (abril 2004)Editorial: Radical-chic 1: l’art entre la complaença i la mala consciència. Inclassificats: Sociology / Xavier Alamany. Publicacions: Cançó, llibre d’artista d’Albert Ràfols-Casamada i Maria Girona. A propòsit de... Fira de Milà: des de l’òrbita del Satellite / Oriol Pibernat. Fet a EINA: Tres cabanes dalt dels arbres / Carles Rodrigo i Gonzalo Sousa Pinto. Publicacions: Presentacio del llibre 02/03. Biblioteca: Informació de qualitat / Teresa Forcadell. Corresponsal: Paris: El savoir-faire a l’Esag Penninghen / Ester Anton. Esag Penninghen / Adriana Campi
Patterns of variation of intertidal species of commercial interest in the Parque Litoral Norte (North Portugal) MPA: comparison with three reference shores
No full textMarine Protected Areas (MPAs) are world-wide established with the aim of conserving biodiversity and preventing overexploitation of marine organisms. Evaluating the effectiveness of MPAs is needed in order to support and implement their management, but it is complicated by the large natural variability in space and time of distribution and abundance of natural populations. Here, we tested the hypothesis that patterns of total abundance and size-frequency distribution of two intensively harvested intertidal species (the sea urchin Paracentrotus lividus and the mussel Mytilus galloprovincialis) differed between a protected and three reference shores along the rocky coast of north Portugal. Response variables were in terms of mean values and measures of variance at different spatial scales (from centimetres to metres) and over time (along a period of about 12 months). A further comparison involved the estimation of the reproductive potential of sea urchins, quantified as variations of Gonad Index (GI = gonad dry weight/body dry weight x 100) at the scale of shore. Results did not generally support a predictable direct effect of protection, as the total abundance and the abundance of larger individuals of both species and Cl did not differ between the MPA and reference shores. However, a considerable temporal and spatial variability at smaller scales was detected for several response variables. Such findings have implications for management of MPAs, highlighting the need for sampling designs properly replicated in space and time, in order to examine their effectiveness, and for considering spatial and temporal heterogeneity of target populations and driving processes as a criterion for their implementation and design
Patterns of recovery of intertidal organisms after compounded anthropogenic disturbances
No full textCoastal habitats are exposed to increasing human and natural disturbances, including extraction of organisms and extreme climatic events. Patterns of recovery (i.e. convergence towards an unmanipulated control) of the structure of benthic assemblages, the total number, and the abundance of individual taxa were examined over a period of 15 mo after the end of a previous experiment. In that experiment, crossed manipulations of levels of mussel harvesting and of the temporal patterns of storm-related mechanical disturbance (in terms of changes in variance but not in the overall intensity) were performed on north Portugal rocky shores. Effects of past disturbances were mostly detected at 3 and 9 mo after the end of disturbances, while no significant differences between unmanipulated and treated assemblages were present after 15 mo. These findings confirm that intertidal assemblages subjected to even extreme combinations of past disturbances can recover in a relatively short time. Important effects present after 3 to 9 mo were associated with the timing of disturbance, likely depending on interactions with life-history traits such as peaks in reproduction and recruitment. Contrary to theories considering disturbances as opportunities for some organisms to replace competitors that dominate space in undisturbed conditions, we observed changes in the abundances of the same taxa rather than their replacement. The present evidence contributes to the understanding of how multiple anthropogenic pressures affect the ability of intertidal assemblages to recover after disturbance
Marginal populations under pressure: spatial and temporal heterogeneity of Ascophyllum nodosum and associated assemblages affected by human trampling in Portugal
No full textAnthropogenic disturbances are major threats to coastal biodiversity and may exert drastic effects on natural populations occurring at the borders of the geographical distribution of species, which are thus already experiencing sub-optimal environmental conditions. In this paper, we examined the effects of experimental intensities of human trampling on temporal and spatial variance of the brown seaweed Ascophyllum nodosum and associated organisms in north Portugal. This is the southernmost population of A. nodosum in Europe and shows morphological and demographic traits that are different from those of populations from more central locations within its range of distribution. Results indicated that high trampling intensity reduced the small-scale spatial heterogeneity in the abundance of A. nodosum, whose cover was stabilized around relatively low values, and of the associated red algae Polysiphonia lanosa and Rhodothamniella floridula; however, it increased the spatial variance of limpets and green foliose macroalgae of the genus Ulva. Idiosyncratic responses in temporal patterns were also documented, with high trampling intensity causing relatively larger fluctuations in the structure of whole A. nodosum associated assemblages and in the abundance of Ulva spp., and smaller fluctuations in the cover of Fucus vesiculosus. The present findings are key to predicting the relatively unstudied responses of coastal populations of A. nodosum to increasing anthropogenic disturbance and have important implications for the management and conservation of the examined population, which represents a relevant component of the biodiversity of European rocky shores
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