1,721,026 research outputs found
Structure and temporal dynamics of marine biodiversity in the Terra Nova Bay area (Ross Sea, Antarctica) analysed through DNA barcoding and metabarcoding: A standardized and systematic approach for the construction of a “DNA Barcode” library.
No full textAims and structure of the thesis:
The firs objective of this thesis consisted in the quantification of the reference library completeness for the Cytochrome c oxidase subunit I (COI) barcode of metazoan species occurring in the Ross Sea MPA and in identifying which taxonomic groups in the last decades were investigated by using “DNA barcode” techniques performed in the Southern Ocean. In order to do that, all the available sequence data on major public repositories were gathered and analyzed. A collection of COI sequences amplified from specimen of the Italian National Antarctic Museum (MNA) was produced and aggregated to the latter to assemble the first global Ross Sea reference library of metazoan COI
barcoding sequences.
The potentialities of “DNA metabarcoding” techniques applied to the analysis of Antarctic biological communities were also evaluated in Terra Nova Bay (TNB) by focusing on the development of macrozoobenthic pioneering communities colonizing artificial structures over a period of three years and on nanoplankton temporal short-term dynamics in two consecutive years. These studies were conducted using innovative sampling methodologies and experiments and differed not only for the investigated community, but also for the sampling frequency, timing and study purposes. Due to the peculiarities of the three analyses, these will be detailed in three separate chapters.
Each chapter is composed by its specific “Introduction” to the concepts discussed in that study, followed by a section on “Materials and Methods” and a joint section with the “Results and Discussion”. Considering that the different chapters, notwithstanding the fact that they pertain to the same, general topic of research, greatly differs in the overall design, as mentioned earlier, no general Discussion for the entire thesis was produced. Instead, an Introduction, discussing the most general topics covered by the entire thesis, is presented at first (i.e. the “Thesis Introduction”), whereas the thesis’ Conclusions, considering all the outcomes reported in the different chapters, will be presented at the end of the whole thesis (“Thesis Conclusions”)
An Analysis of the structure and dynamics of pioneer benthic communities in Terra Nova Bay (Ross Sea, Antarctica) using the Autonomous Reef Monitoring Structures (ARMSs)
No full textIntroduction. The Southern Ocean has unique environmental conditions compared to other areas of the world, making it a key area for the analysis of future biodiversity changes. The peculiarities of this polar ecosystem have played an important role in structuring marine biodiversity, being characterized by high levels of endemism and ecological and cryptic diversity. The data on benthic communities show their marked sensitivity to anthropogenic and climatic changes, impacting both community and species levels. However, these studies have rarely been conducted with reproducible and standardised techniques, limiting our understanding of these changes in both space and time. Here, we present the application of Autonomous Reef Monitoring Structures (ARMSs) to study pioneer benthic communities' development located near the Italian research station Mario Zucchelli in Terra Nova Bay (Ross Sea).
Methods. Each ARMS consists of 10 stacked PVC plates with a 1 cm space to allow for colonization on both surfaces. These structures are characterized by a simplified design, allowing researchers to use more advanced technologies, such as High Throughput Sequencing and photo-analysis to study colonising organisms. The ARMSs were deployed at 25 metres of depth and recovered after 1, 2, 3 and 5 years, respectively. The panels were disassembled, photographed, and the species were identified to the lowest taxonomic level possible. Each photograph was analysed using photo analysis software, highlighting differences in community composition and structure between increasing years of deployment.
Results. The analysis of the data, from one to five years, showed a difference from the point of view of the composition and structure of the communities. They differed particularly according to growth orientation, creating a well-defined structuring depending on the year.
Conclusion. These structures represent the first of their kind to be deployed in Antarctica, providing a fundamental tool for the study of benthic communities, and establishing a baseline against which future population dynamics can be compared
New distributional records of Southern Ocean Isopoda based on vouchers from the Italian National Antarctic Museum (MNA, Section of Genoa)
Full text linkThe order Isopoda Latreille, 1816 consists of species occurring in terrestrial, marine and freshwater environments. In the Southern Ocean (SO), this group is amongst the most speciose and occur at all depths. Isopoda biogeography, despite being studied since the first Antarctic expeditions, is still poorly known from a geographical point of view and shows large occurrence gaps for some groups in specific sectors of the SO. In this paper, we update the isopod checklists of the Ross Sea (RS) and of some peri-Antarctic areas, such as the South Orkney Islands (SOI) and the South Sandwich Islands (SSI), based on the study of museum vouchers curated by the Italian National Antarctic Museum (MNA, Section of Genoa).A total of 279 MNA samples from 15 different expeditions were studied. From this material, consisting of 419 specimens, 41 accepted species distributed in 24 families and 51 genera were identified. Comparing this newly-obtained information with the GBIF (Global Biodiversity Information Facility) and OBIS (Ocean Biodiversity Information System) portal, 15 species are here reported for the first time in the Ross Sea, with five new records in the Ross Sea Marine Protected Area. All records are new for the Terra Nova Bay area, for which a checklist of this group has never been produced before
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
Alcyonidium kuklinskii sp. nov., a new species of Antarctic ctenostome bryozoan with a key to all Antarctic species of the genus
Full text linkRecent surveys of Antarctic waters in the Terra Nova Bay (Ross Sea) revealed numerous bryozoan species including ctenostome bryozoans. Whereas cheilostome bryozoans are well-studied in these latitudes, ctenostomes remain highly neglected. Large ctenostomes are easily recognized by their lack of calcified skeletons, but this lack also renders them difficult and tedious to identify. As a result, histology and reconstructions of internal soft tissues are required to classify this group of bryozoans. Thanks to the availability of new specimens from Terra Nova Bay, a detailed analysis of growth form, gut morphology and tentacle number of two colonies, initially ascribed to the ctenostome bryozoan genus Alcyonidum Lamouroux, 1813, turned out to be a new species, Alcyonidium kuklinskii sp. nov., which we described in this study. These specimens were also barcoded (COI) and sequences compared to available ones. Together with the new species described here, a total of ten species of Alcyonidium is now known for the Southern Ocean, accounting for one eighth of the entire genus diversity. All Southern Ocean species appear to be endemic. In order to speed the identification of the Antarctic Alcyonidium species, we provide an identification key and a distribution map of all type species. In brief, colony morphology, zooidal size and, in particular tentacle number represent the most suitable characters for identifying species within this genus
First results of the macroalgal diversity in Terra Nova Bay (Ross Sea, Antarctica), using DNA barcoding
No full textThe DNA barcoding method is used to screen the macroalgal biodiversity of Terra Nova Bay (Antartide
G4SEE: A Geant4-Based Single Event Effect Simulation Toolkit and Its Validation Through Monoenergetic Neutron Measurements
No full textA single-event effect (SEE) simulation toolkit has been developed at CERN for the whole radiation effects community and released as an open-source code. It has been validated by comparing the simulated energy deposition of inelastic interactions, due to monoenergetic neutrons in the 1.2–17 MeV energy range, to the distribution measured experimentally by a silicon diode detector
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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