1,720,985 research outputs found
Dredging disturbance imprinted in the structure of benthic communities: The case of the Port of Cervia
No full textDredging activities are regularly performed in front the entrance of most of the ports worldwide in order to remove subtidal sandbars, continuously accumulated due to coastal sediment dynamics, and assure minimum depth needed for access. These operations may have severe negative chemical, physical and biological impacts on marine environment (Manap & Voulvoulis, 2015) as well as high economic costs. As possible environmentally and economically friendly alternative, a new technology for seabed maintenance based on “ejectors”, intended to prevent sediment accumulation, is under development. The goal of this research was to analyse macrobenthic communities exposed to dredging activities in front of the Port of Cervia (northern Adriatic Sea) and in the nearby not affected areas, that would serve as a baseline for the evaluation of impacts of new technology that is going to be experimentally deployed in front of this port. Samples were taken in Spring 2018 in the dredged location in front of the Port of Cervia just couple of weeks after the operations and in four control locations, placed 600 m and 1200 m north and south of the impact, at 2-3 m depth range. Two sampling areas were defined in each location and at each area 4 replicated samples of sediment and fauna were taken by SCUBA diving using an aluminium frame (23.5×13.5 cm). In each sample analyses encompassed sediment grain size, percentage of organic matter, dry weight of shell debris and benthic macrofauna (after sieving on 0.5 mm mesh sieve) determination to the lowest possible taxonomic level. Univariate and multivariate analyses were done using software Primer v 6 and PERMANOVA+. Altogether 80 macrofaunal taxa were recorded. Structure of benthic communities was significantly different among sampling locations but not between areas within each location. Dredged location indicated clearly different structure of benthic communities from control ones and showed much higher variation among samples (Figure 1). Impacted communities were characterised by drastically lower species diversity and abundance (Figure 2a, 2b). SIMPER analyses (90% cut off) showed that average similarity in species composition and abundance between samples in control locations was very high (81% to 85%) and due to only three most abundant bivalve species: Lentidium mediterraneum, Donax semistriatus and Chamellea gallina. On the other hand similarity between samples in impacted location was only 37% (characterised by L. mediterraneum and C. gallina). Very high dissimilarity (75% to 80%) in species composition and abundance between impacted and control locations was due to a drastic decrease of abundance of the same three bivalve species on impacted location. Amount of shell debris and the percentage of medium sand (>250 μm) in the sediment were the parameters that had the highest correlation (Rho = 0.716) with the structure of benthic assemblages. Our results indicate that dredging activities had negative impacts both on species richness and abundance, however the settlement of opportunistic species on impacted location was not reported. The three bivalve species mostly characterising benthic assemblages on all locations belong to species sensitive to disturbance, which are characterised by relatively long life, slow growth and high biomass (Simboura and Zenetos, 2002). Communities that are characterized by sensitive species in general show strong effects and slow recoveries of dredging (Kotta et al., 2009). Moreover Chamelea gallina is edible mollusc thus negative impact of dredging on this species, might have economic implications. Several tens of taxa present in control samples weren’t recorded in impacted ones. Although these species weren’t very abundant their ecological importance in benthic communities cannot be neglected. Careful analyses of life traits of these species will have to be performed in order to understand eventual shifts in the functioning of benthic communities
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
Relationships between size and abundance in beach plastics: A power-law approach
Full text linkSandy beaches are one of the most relevant coastal environments in terms of socio-ecological and economical value. So, the presence and accumulation of plastic litter determines a degradation of these values, and calls for management actions for cleaning are required. In this research, we investigated the features of plastic litter distribution on a Mediterranean beach in relation to size and abundance of the sampled items. Simple allometric models were applied with the aim to provide a parsimonious tool for estimating the amount and sizes of the beach plastic litter. The results show effective relations between size and abundance of plastic items according to the power-law distribution. This relationship could support decision-makers to estimate the total amount of beach plastics through the application of a simple model instead of more complex models requiring the estimation of many parameters and the availability of large datasets
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
Conservation of Mediterranean marine benthic biodiversity through innovative, integrative, and standardized methods
No full textEngaging mollusks’ farmers to increase the knowledge on the distribution and impact of non-native species in aquaculture in the Adriatic Sea
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