1,721,099 research outputs found
TRAIT-BASED INDICATORS DEVELOPMENT FOR ASSESSING THE IMPACT OF TRAWLING ACTIVITIES
Full text linkLa selezione delle caratteristiche per lo sviluppo di indicatori per stimare gli impatti della pesca a strascico è cruciale e dovrebbe basarsi su ipotesi ecologiche chiare che collegano la caratteristica al disturbo, tenendo anche conto della qualità delle informazioni. Spesso guidata dal giudizio di esperti o dalla conoscenza comune, la direzione e la valutazione delle modalità delle caratteristiche all'interno dei modelli di indicatori richiedono obiettività. Questa tesi indaga l'efficacia degli approcci basati sulle caratteristiche nel stimare gli impatti della pesca a strascico sulle comunità bentoniche e demersali, in particolare nelle piattaforme continentali del Mediterraneo dove tali attività sono stratificate nel tempo.Inizialmente, una revisione della letteratura ha identificato le principali caratteristiche associate al disturbo della pesca a strascico, le loro direzioni di risposta e le differenze nelle risposte delle caratteristiche tra specie bentoniche, demersali o pelagiche. Ciò ha informato la selezione obiettiva delle caratteristiche per l'analisi. Nel Capitolo 2, sono stati utilizzati sia indicatori basati sui taxa che indicatori funzionali per esaminare le risposte delle comunità bentoniche e demersali in aree intensamente soggette alla pesca a strascico, con l'obiettivo di vedere se le risposte funzionali potessero chiarire gli effetti della pesca a strascico.Il Capitolo 3 ha applicato il framework del Relative Benthic Status (RBS) per valutare gli impatti della pesca a strascico sulle piattaforme continentali intorno alla Sicilia, validando la capacità di generalizzazione, adattabilità, coerenza e sensibilità della metodologia attraverso diversi habitat. Il Capitolo 4 ha sviluppato un nuovo framework basato sulle caratteristiche per valutare la vulnerabilità delle comunità bentoniche alla pesca a strascico, allineandosi con gli obiettivi della Direttiva sulla Strategia Marina (MSFD). Questo capitolo ha fornito feedback sulla selezione delle caratteristiche che contribuiscono ai punteggi finali, confrontando i risultati con metodologie consolidate.Inoltre, il Capitolo 5 ha integrato l'analisi delle caratteristiche biologiche e del disturbo da pesca con le tecnologie di tracciamento del movimento. Ha investigato come l'inclinazione delle porte del peschereccio influisca sulla cattura delle specie nei sedimenti fini, influenzando l'interpretazione dell'impatto basata sui precedenti indicatori.Il Capitolo 6 riassume i risultati, dimostrando come l'analisi della variazione delle caratteristiche supporti la comprensione degli effetti ecologici della pesca a strascico, evidenziando gli impatti e identificando le componenti che guidano la vulnerabilità. Discute anche come le metodologie possano essere adattate ai contesti regionali e come le dinamiche degli attrezzi influenzino la composizione delle catture delle assemblaggi bentoniche-demersali.The selection of traits for developing indicators to estimate the impacts of trawling is crucial and should be based on clear ecological hypotheses linking the trait to disturbance, while also considering information quality. Often guided by expert judgment or common knowledge, the direction and scoring of trait modalities within indicator models require objectivity. This thesis investigates the effectiveness of trait-based approaches in estimating the impacts of trawl fishing on benthic and demersal communities, particularly in Mediterranean continental shelves where such activities are stratified over time.Initially, a literature review identified main traits associated with trawling disturbance, their response directions, and differences in trait responses among benthic, demersal, or pelagic species. This informed the objective selection of traits for analysis. In Chapter 2, both taxon-based and functional indicators were used to examine benthic and demersal communities' responses in intensely trawled grounds, aiming to see if functional responses could elucidate trawling effects.Chapter 3 applied the Relative Benthic Status (RBS) framework to assess trawling impacts on the continental shelves around Sicily, validating the methodology's generalization, adaptability, consistency, and sensitivity across diverse habitats. Chapter 4 developed a novel trait-based framework to assess benthic community vulnerability to trawling, aligning with the Marine Strategy Frameowrk Directive targets. This chapter provided feedback on trait selection contributing to final scores, comparing results with established methodologies.Additionally, Chapter 5 integrated biological traits and fishing disturbance analysis with motion tracking technologies. It investigated how trawl door inclination affects species capture on fine sediments, influencing impact interpretation based on previous indicators.Chapter 6 summarizes the findings, demonstrating how trait variation analysis supports understanding the ecological effects of trawling, highlighting impacts, and identifying vulnerability-driving components. It also discusses how methodologies can be tailored to regional contexts and how gear dynamics influence catch composition of benthic-demersal assemblages
Extirpation-resistant species do not always compensate for the decline in ecosystem processes associated with biodiversity loss
No full textAccelerating rates of biodiversity loss may result in a rapid decline in important ecosystem processes such as carbon capture. Whether extirpation-resistant species compensate for the decline in ecosystem processes associated with the loss of extirpation-prone species is poorly understood.We apply a novel approach to answer this question using an assemblage of salt marsh plants. First, manipulations were performed to simulate a realistic sequence of species loss, based on observed sensitivity to disturbance. Then, changes in biomass and primary production of extirpation-resistant species were monitored over three consecutive growing seasons.Extirpation-resistant species did not compensate for the loss of either biomass or primary production associated with the removal of extirpation-prone species. Factors that determine the potential for compensation within ecosystems are discussed. These include resource-regulated compensation rates, the level of functional redundancy within an assemblage and the extirpation resistance of species which possess good compensation traits. Synthesis. These results suggest that we cannot assume extirpation-resistant species will compensate for the decline in ecosystem processes associated with biodiversity loss across all ecosystems. Understanding those factors that influence the ability of ecosystems to compensate for declines in ecosystem processes associated with biodiversity loss constitutes a significant challenge
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
Identifying Foraging Behaviour of Wild Bottlenose Dolphins (Tursiops truncatus) and Harbour Porpoises (Phocoena phocoena) with Static Acoustic Dataloggers
No full textSound is the main means of communication for cetaceans, and studying their vocal behaviour can reveal important information about their activity patterns. As static acoustic monitoring (SAM) of whales, dolphins, and porpoises becomes more widespread, it is important to understand how data collected with automated click loggers relate to their behaviour. To assess whether behaviour can be inferred from automated click train data, echolocation click trains (series of clicks) of bottlenose dolphins and harbour porpoises recorded by C PODs were examined with simultaneous visual observations. Recorded click trains from both species had different characteristics for the two observed behavioural categories: (1) travelling and (2) foraging. Foraging click trains for both species were of shorter duration and had shorter inter-click intervals. The distinction in the click trains between the two behaviours was stronger for harbour porpoises. More than one quarter of the harbour porpoise click trains represented a distinct group of very fast click trains or “buzzes,” which were thought to be associated with foraging, whereas only a small fraction of such trains was found in the bottlenose dolphin click data. For both species, the C PODs showed potential in detecting foraging behaviour and in identifying potential feeding sites and trends in foraging activity
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
Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment
Full text linkMicrobes and benthic macro-invertebrates interact in sediments to play a major role in the biogeochemical cycling of organic matter, but the extent to which their contributions are modified following natural and anthropogenic changes has received little attention. Here, we investigate how nitrogen transformations, ascertained from changes in archaeal and bacterial N-cycling microbes and water macronutrient concentrations ([NH4–N], [NO2–N], [NO3–N]), in sand and sandy mud sediments differ when macrofaunal communities that have previously experienced contrasting levels of chronic fishing disturbance are exposed to organic matter enrichment. We find that differences in macrofaunal community structure related to differences in fishing activity affect the capacity of the macrofauna to mediate microbial nitrogen cycling in sand, but not in sandy mud environments. Whilst we found no evidence for a change in ammonia oxidiser community structure, we did find an increase in archaeal and bacterial denitrifier (AnirKa, nirS) and anammox (hzo) transcripts in macrofaunal communities characterized by higher ratios of suspension to deposit feeders, and a lower density but higher biomass of sediment-reworking fauna. Our findings suggest that nitrogen transformation in shelf sandy sediments is dependent on the stimulation of specific nitrogen cycling pathways that are associated with differences in the composition and context-dependent expression of the functional traits that belong to the resident bioturbating macrofauna community
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