1,720,957 research outputs found
The influence of ocean warming on the provision of biogenic habitat by kelp species
No full textKelp forests represent some of the most productive and diverse habitats on Earth, and play a critical role in structuring nearshore temperate and subpolar environments. They have an important role in nutrient cycling, energy capture and transfer, and offer biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and generate three-dimensional habitat structure for a vast array of marine plants and animals, including a number of ecologically and commercially important species. This thesis aimed to describe the role of temperature on the functioning of kelp forests as biogenic habitat formers, predominantly via the substitution of cold water kelp species by warm water kelp species, or through the reduction in density of dominant habitat forming kelp due to predicted increases in seawater temperature. The work comprised three main components; (1) a broad scale study into the environmental drivers (including sea water temperature) of variability in holdfast assemblages of the dominant habitat forming kelp in the UK, Laminaria hyperborea, (2) a comparison of the warm water kelp Laminaria ochroleuca and the cold water kelp L. hyperborea as habitat forming species, and further investigation into the impacts of this subtle climate driven substitution of habitat forming kelps, and (3) experimental manipulation of densities of the dominant intertidal kelp in the UK, Laminaria digitata, in order to understand the impacts of climate driven loss of a dominant habitat forming species.L. hyperborea assemblages varied significantly between study regions spanning ~9° of latitude, as well as between and within sites at a local scale. Patterns in mobile and sessile assemblage structure were driven principally by different environmental factors. Overall patterns in the structure of biogenic habitat and assemblage structure did not vary predictably with latitude, indicating that other processes acting across multiple spatial scales are important drivers of assemblage structure.L. ochroleuca hosted impoverished assemblages associated with both holdfasts and stipes, compared with L. hyperborea. Further, climate driven increases in the relative abundance of L. ochroleuca relative to L. hyperborea lead to disruption of an important habitat cascade associated with the stipe of L. hyperborea and epiphytic algae. L. ochroleuca stipes typically lack the dense epiphytic assemblage associated with L. hyperborea, and host depauperate faunal assemblages which may have impacts on higher trophic levels.Experimental reduction in the density of L. digitata led to a dramatic shift in dominance from perennial to annual species, particularly the pseudo-kelp Saccorhiza polyschides on an exposed rocky shore. Impacts on a sheltered shore were subtler, and may have been tempered by the presence of another perennial kelp, Saccharina latissima. Loss of L. digitata led to a reduction in the standing stock of macroalgae after ~2.5 years of manipulation on both shores. These findings have significant implications for the structure and functioning of rocky shores in the future.Overall, anthropogenic climate change is likely to negatively impact the functioning of kelp forests as repositories of biodiversity in the future via the reshuffling of warm- and cold-water kelp species and through an overall loss of algal biomass and associated habitat due to continued increases in seawater temperature in the northeast Atlantic
Climate-driven substitution of habitat-forming species leads to reduced biodiversity within a temperate marine community
No full textAim: In marine ecosystems, habitat-forming species (HFS) such as reef-building corals and canopy-forming macroalgae alter local environmental conditions and can promote biodiversity by providing biogenic living space for a vast array of associated organisms. We examined community-level impacts of observed climate-driven shifts in the relative abundances of two superficially similar HFS, the warm-water kelp Laminaria ochroleuca and the cool-water kelp Laminaria hyperborea. Location: Western English Channel, north-east Atlantic Methods: We compared algal and invertebrate assemblages associated with kelp stipes and holdfasts, across multiple sites and sampling events. Significant differences were recorded in the structure of assemblages between the host kelp species at each site and event. Results: Assemblages associated with stipes of the cool-water HFS were, on average, >12 times more diverse and supported >3600 times more biomass compared with the warm-water HFS. Holdfast assemblages also differed significantly between species, although to a lesser extent than those associated with stipes. Overall, assemblages associated with the warm-water HFS were markedly impoverished and comprised far fewer rare or unique taxa. Main conclusions: While previous research has shown how climate-driven loss of HFS can cause biodiversity loss, our study demonstrates that climate-driven substitutions of HFS can also lead to impoverished assemblages. The indirect effects of climate change remain poorly resolved, but shifts in the distributions and abundances of HFS may invoke widespread ecological change, especially in marine ecosystems where facilitative interactions are particularly strong.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<i>Laminaria hyperborea</i>) in the northeast Atlantic - Fig 2
Full text linkMap indicating the locations of the four study regions in the UK, northeast Atlantic: (A) northern Scotland, (B) western Scotland, (C) southwest Wales and (D) southwest England. Smaller panels show the positions of the 3 study sites within each region.</p
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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