1,721,018 research outputs found
Size Density Relationships: a Cross-Community Approach to Benthic Macroinvertebrates in Mediterranean and Black Sea Lagoons
No full textAn integrated individual-level trait-based phytoplankton dataset from transitional waters
No full textLinking classification boundaries to sources of natural variability in transitional waters: A case study of benthic macroinvertebrates
No full textThe assessment of human impacts on aquatic ecosystems requires separate quantification of natural and anthropogenic sources of environmental variability. This statement is very challenging in some categories of water bodies such as transitional waters, because they are naturally stressed ecosystems in which natural variability occur on different spatial scales (gradients versus patchiness) and temporal scales (regular versus pulse events). Among transitional water quality elements, benthic macroinvertebrates are the most exposed to natural variability patterns due to their life cycles and space-use behavior. In this article, we have evaluated the relevance of different potential sources of natural variability of benthic macroinvertebrate guilds on the temporal and spatial scales and we have quantified their effects on simple and multimetric descriptors of macroinvertebrate guilds; the latter included biomass and numerical densities, taxonomic diversity as well as M-AMBI and index of size spectra, ISS. The study was carried out using the TWReferenceNET database of 14 Eastern Mediterranean and Black Sea lagoons. Synoptic sampling of benthic macroinvertebrates was performed seasonally in different habitats within each lagoon in accordance with a nested design. All considered metrics showed a relatively high degree of variability among different reference stations and ecosystems, with the coefficient of variation ranging from 20% (log numerical density) to 45% (M-AMBI). The average values of every metric were significantly affected by the considered natural sources of variation: lagoon typology, seasonal period and habitat patchiness. Among components of lagoon typology, water salinity influenced the most the variation for both simple and multimetric descriptors. Seasonal period also had a strong influence, with higher values for all metrics before the summer season compared to the one after summer. Benthic habitat patchiness had a considerable influence only on the simple metrics, while continuous habitat variables significantly affected both M-AMBI and ISS. A general mixed model approach, used to quantify the relative influence of the different sources of variation on the considered metrics, allowed calculating type-specific boundaries for M-AMBI and ISS. The new boundaries significantly improved the accuracy of both multimetric indices in the classification of studied reference condition sites, with more than 75% of stations classified as good or high status. Nonetheless, results show that there is an intrinsic uncertainty in the classification of ecological status of lagoon ecosystem due to the degree of variability under reference conditions
Length–mass relationships for transitional water benthic macroinvertebrates in Mediterranean and Black Sea ecosystems
No full textUncertainty of macroinvertebrate body-sizes derived by length per weight relationships, taxonomic sufficiency and influence on the ISS ecological indicator: a study case in Lesina lagoon (Mediterranean Ecoregion, Italy)
No full textIndicators based on body-size metrics have been recently developed and applied. Despite of the implication of body-size in ecological status assessment, the determination individual biomass of benthic macroinvertebrates (BM) is a complicate, time-consuming, time-lag, and expensive procedure. They are the greater limitation in the application of body-size based indicators, specifically for the new multi-metric Index of Size Spectra (ISS). The aim of the research was to test simplifying procedures for a more user-friendly application of body-size based indicators in transitional waters. The research was performed in the Lesina lagoon (Mediterranean ecoregion, Italy). We evaluated the uncertainty of estimating the individual biomass (IB) of BM applying the length per weight relationships (LWRs), obtained at species and order level. Than we compared the ISS using: 1. direct measures of IB of site/sampled BM; 2. indirect measures of IB obtained by LWRs at species and order taxonomic levels; 3. indirect measures of IB obtained by LWRs of a previous dataset realized in Lesina; 4. indirect measures of IB obtained by LWRs at species and order levels of a previous dataset realized in different sites. The accuracy of body-size spectra and ISS achieved with the different direct and indirect measures of individual biomass will be described and compared in the light of developing simple, rapid and accurate biomonitoring tools for the ecological assessment of transitional waters
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
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