1,720,979 research outputs found
Study of the macrophyte assemblages and application of phytobenthic indices to assess the Ecological Status of the Marano-Grado Lagoon (Italy)
No full textAbstract
Benthic macrophytes from 19 sites within the Marano-Grado Lagoon were sampled in July 2007 in
order to update the available information on the flora and vegetation and to assess the Ecological
Status (ES) within the European Water Framework Directive (WFD). Data on macrophytes were
analysed using two phytobenthic indices (EEI and R-MaQI) recently set up to evaluate the
ecological status of transitional environments in the Mediterranean eco-region. Notwithstanding the
extension (c. 160 km2) that places this lagoon as the second largest Italian transitional environment,
ecological studies are relatively few. The present research revealed a relatively poor flora, mainly
characterized by the dominance of low-diversity settlements of Ulvaceae. Moreover, the absence of
intensive aquaculture activities and commercial big harbours, which account for the new species
introductions recorded in other lagoons, limits the presence of non-autochthonous species. The
comparison with previous data (Curiel et al. 1998) highlighted the reduction of macrophyte
coverage and biomass, especially Ulvaceae stands, and an increase in species richness. In particular,
there was evidence of a worsening of the area north of the Grado bridge. This area, which in the
past was colonized by widespread angiosperm coverage, at present is almost lacking in vegetation.
According to these observations, by applying both the phytobenthic indices available in the
literature for the transitional environments, the Marano-Grado Lagoon showed a ‘Good–High’
quality in the central part of the basin and near the lagoon inlets and a ‘Poor–Bad’ quality in the
northern and southern areas. The evaluation of some physicochemical parameters, coupled with the
distribution of the angiosperms, also allowed a first delineation of the main lagoon water bodies
Applicability and intercalibration of macrophyte quality indices to characterise the ecological status of Mediterranean transitional waters: the case of the Venice lagoon.
No full textIn the framework of the WFD 2000/60/EC intercalibration process the updated versions of the EEI and R-MaQI, proposed by Italy and Greece for the transitional waters, have been applied to the macrophytes of the Venice lagoon to test their comparability and relationships with the pressure gradients. Submerged macrophytes were collected during spring 2007 at 60 sites spread within the lagoon. At each site, five random samples were collected and the total coverage of benthic macrophytes in the field was estimated based on a number of tests of the bottom. To assess seagrass epiphytes, five shoots were collected for each replicate. Physico-chemical data were collected in the water column at 14 sites selected to reflect the main hydro-geomorphological and trophic gradients of the lagoon. The analyses performed indicated that the two metrics appeared to be weakly intercalibrated and only the 30% of the sampling sites displayed the same quality class. The main differences fell into the Moderate and Low classes and the two indices provided discordant results in the intermediate and confined areas of the lagoon. In contrast, the two indices showed good affinity in the marine areas of inlets, which are characterised by seagrass meadows and late-successional macroalgae. Similar results were evidenced also in a redundancy analysis by the different relationships between quality classes and the physico-chemical gradients. The main reason for this seems to be the heterogeneity of species–environment relationships inside the groups of species on which the indices are based. Critical aspects of methodological differences and applicability of the macrophyte indices proposed by Italy and Greece for the transitional waters of the Mediterranean eco-region are discussed
RINVENIMENTO DI UNA RARA MACROALGA PER LA LAGUNA DI VENEZIA: PHYMATOLITHON LENORMANDII (ARESHOUG) W. H. ADEY (CORALLINALES, RHODOPHYTA)
No full textAbstract
The recovery and the morphological description of a rare encrusting calcareous species Phymatolithon
lenormandii
(Areshoug) W. H. Adey (Corallinales, Rhodophyta) are reported for the Lagoon of Venice. This species may
be considered endangered and vulnerable since it has not been yet signalled within the last two hundred
years
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
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