1,720,960 research outputs found
Recovery and restoration of marine endangered habitats
Full text linkLa biodiversità marina regola il funzionamento ecosistemico, responsabile della produzione di beni e servizi importanti per la biosfera ed il benessere umano. I cambiamenti climatici globali e le attività umane stanno alterando la biodiversità degli oceani ed il funzionamento ecosistemico. Al momento, partendo dalla consapevolezza che le sole misure di conservazione non sono sufficienti a invertire la degradazione degli ecosistemi, è riconosciuto che il restauro ambientale è una azione di cruciale importanza per far fronte a questa minaccia. Tuttavia, è necessaria una maggiore conoscenza scientifica per rendere efficaci azioni di restauro, specialmente negli ambienti profondi che sono largamente sconosciuti. Tra le maggiori attività che avranno impatti sugli habitat marini vi sono lo sfruttamento di risorse minerarie e la pesca a strascico, le quali, risospendendo particelle polimetalliche e sedimenti, avranno effetti principalmente sulle specie bentoniche. In questa tesi, il Corallium rubrum, specie strutturante di elevata valenza ecologica, è stato esposto a questi due tipi di particolato. Dopo la rimozione della fonte di impatto, questo organismo è in grado di recuperare parzialmente tassi di alimentazione e la sua integrità tissutale. Questo esperimento fornisce utili informazioni non solo per meglio comprendere gli effetti di tali attività su organismi bentonici, ma anche per definire possibili misure di mitigazione attraverso una modulazione appropriata della loro intensità e durata.
Allevare in acquario specie di corallo minacciate potrà essere utile per futuri progetti di restauro che prevedono il trapianto di colonie donatrici. Una dieta appropriata da somministrare durante l’allevamento può avere effetti benefici sulla loro crescita ed il loro successo riproduttivo. In questa tesi, è stata studiata la selezione di cibo da parte di alcuni coralli profondi (Desmophyllum pertusum, Madrepora oculata and Dendrophyllia cornigera), i quali hanno mostrato una preferenza per il crostaceo Mysis relicta. I risultati ottenuti dalle analisi condotte sugli isotopi stabili hanno inoltre fornito nuove informazioni sulle nicchie trofiche occupate nel Mar Mediterraneo da queste specie.
Una volta ampliate le conoscenze sugli habitat e le specie da restaurare, è necessario valutare l’efficacia delle procedure di rispristino che si vogliono applicare. In questa tesi, sono stati studiati gli effetti di due esperimenti pilota di trapianto della fanerogama Cymodocea nodosa e della gorgonia Eunicella singularis su attributi di funzionamento ecosistemico. I risultati ottenuti indicano che il trapianto di tali organismi, se opportunamente pianificato, non solo garantisce la loro sopravvivenza, ma può anche avere effetti positivi su processi ecosistemici chiave.
Tuttavia, sono necessari ulteriori studi per valutare la possibile estensione di queste azioni per affrontare l'attuale scala spaziale di perdita di specie/habitat. Questo lavoro fornisce nuovi elementi per la comprensione dei potenziali benefici ecologici derivanti dal restauro ambientale e delle sue ricadute per la conservazione del capitale naturale.Marine biodiversity regulates ecosystem functions, which are responsible for the production of goods and services for the biosphere and human well-being. Global changes and human activities are altering ocean biodiversity and ecosystem functioning. At present, stemming from the awareness that conservation and management are often not enough to halt and revert the degradation of threatened ecosystems, it has been recognized that active restoration is crucial to cope with this issue. More knowledge is needed to make restoration actions effective, especially for the largely unknown deep ocean. Two of the main activities that will alter marine habitats are ore exploitation and bottom trawling that, resuspending polymetallic and sediment particles, will affect benthic species. In this thesis, the habitat-forming species Corallium rubrum was exposed to these types of particles. After the removal of the disturbance, its feeding rates and tissue integrity partially recovered. This experiment provides new insights on the consequences of these activities as well as on potential mitigation strategies by properly modulating their intensity and duration.
Rearing endangered corals in aquaria can be useful for future projects that aim to restore degraded reefs by transplanting healthy colonies. An appropriate diet may positively impinge on their growth or reproduction success. In this perspective, I studied the food selection of cold-water corals (Desmophyllum pertusum, Madrepora oculata and Dendrophyllia cornigera) was studied and these species showed a preference for the crustacean Mysis relicta. Stable isotope analyses provided also novel information on the trophic niches occupied by these coral species in the Mediterranean Sea.
After expanding the knowledge on the habitat or the species to be restored, it is necessary to evaluate the effectiveness of the restoration actions that it might be applied. In this thesis, the effects of two pilot transplantation experiments of the seagrass Cymodocea nodosa and the gorgonian Eunicella singularis on ecosystem functioning of surrounding sediments have been studied. The results showed that transplantation can be effective and that it can have also positive effects on key-ecological processes. However, further studies are needed to assess the potential of scaling-up these actions addressing the present scale of species/habitat loss. This work provides new elements for a better understanding of the potential ecological benefits that can contribute to the conservation of the natural capital
Restoration of Cymodocea nodosa seagrass meadows: efficiency and ecological implications
No full textSeagrass meadows play a key role in the provisioning of ecosystem goods and services. These systems are extremely vulnerable to multiple anthropogenic impacts. Therefore, there is an urgent need to develop new techniques to efficiently restore degraded seagrass meadows. Here we tested the efficacy and efficiency of a new technique of seagrass transplant (Cymodocea nodosa) using biodegradable containers. We investigated the effects of this transplant technique in the Adriatic Sea comparing the transplanted seagrass meadows with adjacent donor seagrass meadows and bare sediments used as control. We assessed the recovery rates and the ecological implications of this transplant on key ecosystems functions, including the biomass and detritus provision to local biological communities, and the effects on the biodiversity of the associated benthic fauna. Our results show that this restoration technique was successful, enabling the seagrass survival (approximately 30%) even in high-energy conditions occurring in winter. The sediments hosting the transplanted seagrasses showed an increase of trophic availability and of rates of organic matter cycling. Despite this, 1 year after the transplant, the abundance and biodiversity of meiofaunal assemblages in the restored seagrasses were still lower than in donor seagrass meadows. These results indicate that the restoration process of seagrass meadows can take a long time, and that a multilevel approach (including the analysis of biodiversity and of the sedimentary processes and biogeochemical cycles) is needed to assess the success of restoration actions in these habitats
Seasonal Trophic Ecology and Diet Shift in the Common Sole Solea solea in the Central Adriatic Sea
No full textThe common sole, Solea solea, is one the most important commercial species in Europe and, within the Mediterranean, the Adriatic basin is the most crucial area for its production. Although the species is overexploited in the basin, data on its trophic ecology are fragmentary, even though this is one of the most important features within the Ecosystem Approach to Fishery. Here, we analysed temporal variations in the feeding ecology of the species by using an integrated approach of stomach contents and stable isotope analyses coupled with the analysis of some condition indices such as the gonadosomatic and the hepatosomatic indices. Changes in diet and trophic level across the years in adult females were clearly linked to the different energetic requirements facing reproduction. Temporal changes throughout the year were mainly related to changes in food availability. This study confirms the opportunistic behaviour of this benthophagous species and its role as a mesopredator, opening new perspectives for further investigations on the effects of the overexploitation of this important fishery resource on the marine trophic web
Resource Partitioning among “Ancillary” Pelagic Fishes (Scomber spp., Trachurus spp.) in the Adriatic Sea
No full textThe Mediterranean is one of the most overfished seas of the world where mesopredators are severely threatened. The trophic strategies of four pelagic species that inhabit the Adriatic Sea (Scomber spp. and Trachurus spp.) were investigated through an integrated approach of stomach contents and stable isotopes analyses. Our study demonstrated that Scomber colias feeds mainly on strictly pelagic prey, with fish larvae as a secondary prey in the Southern Adriatic Sea, while S. scombrus feeds on prey belonging to higher trophic levels. Smaller specimens of Trachurus mediterraneus have a diet mainly based on pelagic prey, while larger fishes rely on prey such as benthic decapods, showing an ontogenetic shift in the diet of the species. Trachurus trachurus shows a preference for offshore and deeper areas and a diet such as that of its congeneric, but no clear ontogenetic shift was observed. This spatial segregation allows the co-existence of these two species of Trachurus. Scomber colias mainly inhabits southern areas and S. scombrus shows a preference for the northern sectors. This latitudinal gradient avoids the overlap of their trophic niches. Bayesian mixing models confirmed that the trophic niches of these species only partially overlap in the middle of the trophic web
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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