1,720,969 research outputs found
Biodiversity and Trace Elements: Community Assessments and Application of Benthic Organisms as Biomonitors of Environmental Pollution
Full text linkL’applicazione di organismi bioindicatori, per descrivere possibili cambiamenti dovuti a impatti antropici o naturali, è aumentata negli ultimi decenni grazie all’implementazione della legislazione Europea (es., Water Framework Directive, Marine Strategy). In quest’ottica il monitoraggio periodico delle comunità marine assume un ruolo cruciale. Obiettivo di questo progetto è stato la caratterizzazione delle comunità a idroidi (Cnidaria:Hydrozoa) e spugne (Porifera) delle isole di Montecristo e Giglio, appartenenti al Parco Nazionale dell’Arcipelago Toscano destinato a futura istituzione come Area Marina Protetta. Oltre ad aumentare le conoscenze sulle comunità marine delle due isole, i risultati ottenuti sono stati resi disponibili agli stakeholders per informarli sulle specie dei gruppi considerati presenti nell’area, sperando che possa essere d’aiuto nell’implementazione di nuove strategie di protezione. Inoltre, è stata condotta una revisione sistematica sull’applicazione di organismi bentonici (spugne, cnidari, briozoi, policheti, cirripedi, tunicati), proposti come bioindicatori non-convenzionali di elementi in tracce per le aree marine costiere. Infatti, ulteriore obiettivo del progetto è stato quello di esplorare il ruolo dei poriferi come bioindicatori di inquinamento da mercurio (Hg), tramite un’analisi multilivello (dalla comunità al gene). Grazie a uno studio preliminare su diverse specie, alcune sono state suggerite come migliori bioindicatori, tra cui Chondrosia reniformis, considerata per analisi successive. Infine, è stato esplorato il ruolo del microbiota associato alle spugne nei processi di bioaccumulo, per poter proporre questi organismi nella bioremediation. Oltre ad una caratterizzazione della comunità microbica di C. reniformis, quantità considerevoli di Hg sono state ritrovate all’interno del microbiota stesso, suggerendo suo un coinvolgimento non solo nel metabolismo secondario delle spugne, ma anche nei processi di bioaccumulo di Hg.Periodic biodiversity assessments are of fundamental importance for describing possible changes in marine communities caused by natural or anthropogenic impacts. The application of different organisms as bioindicators of impacts and pollution has increased in the last decades thanks to the implementation of the European legislation (e.g., Water Framework Directive, Marine Strategy). In this context, the aim of this PhD project was to assess the hydroid (Cnidaria:Hydrozoa) and sponge (Porifera) communities of Montecristo and Giglio, two islands belonging to the Tuscan Archipelago National Park aimed to become a future Marine Protected Area. These data improve the knowledge on the zoobenthic communities of the studied area and have been also made available to stakeholders and policy makers, to inform them on the hydroid and sponge species present in the studied area, possibly helping in the implementation of new protection strategies. A systematic review was also conducted on the application of benthic organisms (sponges, cnidarians, bryozoans, polychaetes, cirripeds, tunicates), suggested as non-conventional bioindicators of trace elements in coastal shallow waters. In fact, this project also deepens the application of Porifera as biomonitoring tools for mercury (Hg) pollution, with a multi-level analysis (from the community to the individual). Thanks to a preliminary study on different species, a few were suggested as better bioindicators of Hg, among them the species Chondrosia reniformis, which was considered for further analysis. In addition, the role of sponges’ associated microbiota in the bioaccumulation processes was explored to identify these organisms also as useful tools in the bioremediation. The microbial community of the C. reniformis was characterized, and considerable amount of metal were detected in the microbiota itself, suggesting its possible implication not only in the secondary metabolism of the sponge but also in the bioaccumulation of Hg
Short-term effects of environmental factors on the asexual reproduction of Aurelia sp. polyps
No full textAurelia is a jellyfish genus common in coastal and estuarine habitats, that are typically affected by human pressures such as heavy metals contamination. Mercury is one of the most dangerous due to its high toxicity, persistence and bioaccumulation. In this paper, we tested for the first time the independent and combined effects of a level of mercury allowable by European regulation in force and hyposalinity on the asexual reproduction of Aurelia sp. polyps, mirroring a realistic scenario. Both mercury (0.07 μg/L, Maximum Allowable Concentration) and salinity (18 and 23 PSU) and the combination of the two factors stimulated the asexual reproduction increasing the number of polyps and buds during the 41 days of experiments. The increment of the asexual reproduction and the absence of suffering and mortality suggest that levels of mercury below the concentration fixed by the law and hyposalinity conditions could promote jellyfish proliferations, according to the hormesis hypothesis
Distribution of mercury inside the Mediterranean sponge Chondrosia reniformis: A study case from the Tuscan Archipelago National Park (Tyrrhenian Sea)
Full text linkTrace elements are ubiquitous substances in the marine environment, representing a problematic hazard for organisms since many of them lack any biological function. The main aim of the study was to investigate the variation of the total mercury content (THg) in the Mediterranean sponge Chondrosia reniformis collected in two islands of the Tuscan Archipelago, Italy. The two islands did not show harmful levels of THg (seawater and sediment) and no intraspecific variability was detected in THg values and bioconcentration factors of collected samples. Conversely, THg values recorded in the choanosome of C. reniformis were significantly higher than in the cortex, pointing out a possible involvement of the sponge microbiota in the bioaccumulation process. Our study suggests that C. reniformis could be an attractive bioindicator of toxic elements pollution in coastal waters, highlighting the potential use of these organisms in the monitoring programs of coastal areas, as suggested by various European marine policies
Sponges associated with Antarctic stylasterids (Cnidaria, Hydrozoa) from the deep Ross Sea: what’s new?
No full textIn 2017, during the XXXII Antarctic campaign on board R/V Italica, in the context of the PNRA research project GRACEFUL (PNRA16_00069), several deep (670-1022 m) remotely operated vehicle (ROV) explorations in the Ross Sea documented wide areas of thanatocoenosis and scattered living colonies of stylasterids. These aggregations of stylasterids create a secondary substrate defined as a ‘deep marine animal forest’ that supports a high biodiversity of associated sponges. A total of 228 sponges, belonging to 38 species, was recorded attached on Inferiolabiata labiata (Moseley, 1879) fragments. The most abundant species is Iophon radiatum Topsent, 1901, with 47 specimens, followed by Clathrochone cf. clathroclada (Lévi & Lévi, 1982) with 24 specimens and Clathria paucispicula (Burton, 1932) with 17. Ten species are first records from the Ross Sea, one species (Halichondria (Halichondria) cristata Sarà, 1978) represents a first record from Antarctica, and other 9 species are probably new to science.
Very low levels of coral coverage by sponges were found despite the large number of species. On average, we estimated the presence of 2 species per fragment of I. labiata with a maximum of 8 species on a single colony fragment. All the sponge specimens were very small and did not exceed 5 cm2, while 81% of the sponge samples ranged between 0.003 - 0.5 cm2. In fact, these stylasterids represent an available secondary substrate, but being dead, they are prone to be covered by bottom sediments, while filter-feeding epibionts usually prefer living and elevated substrates.
Data from our surveys indicated a rich and diverse sponge fauna associated with stylasterid thanatocoenosis in deep Antarctic waters, in line with the known levels of diversity of this region
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
The prokaryotic community of Chondrosia reniformis Nardo, 1847: from diversity to mercury detection
Full text linkMicrobial communities inhabiting sponges are known to take part in many metabolic pathways, including
nutrient cycles, and possibly also in the bioaccumulation of trace elements (TEs). Here, we used high-throughput, Illumina sequencing of 16S rRNA genes to characterize the prokaryotic communities present in the cortex and choanosome, respectively the external and internal body region of Chondrosia reniformis, and in the surrounding seawater. Furthermore, we estimated the total mercury content (THg) in these body regions of the sponge and in the corresponding microbial cell pellets. Fifteen prokaryotic phyla were detected in association with C. reniformis, 13 belonging to the domain Bacteria and two to the Archaea. No significant differences between the prokaryotic community composition of the two regions were found. Three lineages of ammonium-oxidizing organisms (Cenarchaeum symbiosum, Nitrosopumilus maritimus, and Nitrosococcus sp.) co-dominated the prokaryotic community, suggesting ammonium oxidation/nitrification as a key metabolic pathway within the microbiome of C. reniformis. In the sponge fractions, higher THg levels were found in the choanosome compared to the cortex. In contrast, comparable THg levels found in the microbial pellets obtained from both regions were significantly lower than those observed in the corresponding sponge fractions. Our work provides new insights into the prokaryotic communities and TEs distribution in different body parts of a model organism relevant for marine conservation and biotechnology. In this sense, this study paves the way for scientists to deepen the possible application of sponges not only as bioindicators, but also as bioremediation tools of metal polluted environments.info:eu-repo/semantics/publishedVersio
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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