1,720,958 research outputs found
Impact of ocean acidification on microbial assemblages and marine biogeochemistry
No full textSi conosce ancora poco riguardo la risposta delle comunità microbiche eterotrofe marine all’acidificazione oceanica e le conseguenze sulle reti trofiche e i cicli biogeochimici negli oceani. La maggior parte delle nostre conoscenze derivano da esperimenti manipolativi a breve termine. Studi in situ di aree caratterizzate da naturali variazioni di pH, possono aiutare a comprendere gli effetti dell’acidificazione oceanica a livello ecosistemico, prendendo in considerazione le complesse interazioni microbiche esistenti in ambienti naturali. In questo studio abbiamo investigato gli effetti dell’acidificazione oceanica sulla struttura e il funzionamento delle reti trofiche microbiche pelagiche e bentoniche e dei cicli biogeochimici in due aree costiere del Mediterraneo, caratterizzate da naturali condizioni di acidificazione, paragonabili agli scenari futuri previsti per l’anno 2100 e 2500. A Presidiana (Sicilia) la naturale acidificazione era dovuta ad un input terrestre di acque a bassa salinità, nell’isola di Ischia era associata all’attività di vents vulcanici. I nostri risultati hanno mostrato che le condizioni di acidificazione causavano nei sedimenti un aumento della biomassa algale e delle attività enzimatiche extracellulari, con conseguente diminuzione del contenuto di materia organica a valori estremi di pH (<7). Bassi valori di pH in acqua causavano una riduzione della biomassa fitoplanctonica e della materia organica particellata e, associati a bassi valori di salinità, avevano un effetto negativo sulle attività enzimatiche extracellulari. Tuttavia in entrambi i sistemi investigati, valori di pH attesi per il 2100 hanno mostrato un significativo impatto su procarioti e virus pelagici e bentonici e sulle loro interazioni, causando un aumento della produzione virale e della mortalità procariotica indotta dai virus. L’infezione virale era favorita ulteriormente dall’aumento dell’attività enzimatica specifica delle singole cellule procariotiche. Al maggiore impatto virale era associato anche un cambiamento nella composizione di comunità batteriche e una diminuzione di diversità. Riduzioni estreme di pH sono risultate invece sfavorevoli alle attività virali influenzando negativamente le interazioni virus-procarioti e riducendo la pressione virale sulle comunità microbiche.We still know little about the response of heterotrophic microbial communities to ocean acidification and the consequences for marine food webs and biogeochemical cycles. Most of our knowledge is derived from short-term perturbation experiments. In situ observational studies, exploiting natural pH gradients, can help to understand the ecosystem level effects of ocean acidification, taking into account the complex microbial interactions and environmental conditions. In this study we investigated the effects of ocean acidification on the structure and functioning of pelagic and benthic microbial food webs and biogeochemical cycling in two coastal areas of the Mediterranean Sea, characterized by naturally acidified conditions, comparable to near future (i.e., 2100) and extreme (i.e., 2500) scenarios. At Presidiana (Sicily) the natural acidification was due to freshwater input from inland, at Island of Ischia was associated with volcanic CO2 vents. Our results showed that in the sediment the acidification caused an increase of algal biomass and of extracellular enzymatic activities, with a consequently decrease of biochemical components at extremely low pH values (<7). Low pH values in seawater caused a reduction of phytoplankton biomass and of suspended organic matter and, associated to low salinity, affected negatively the extracellular enzymatic activities. However in both investigated systems, pH values expected for a near future scenario, had a significant impact on pelagic and benthic prokaryotes and viruses and on their interactions, increasing viral production and prokaryotic mortality induced by viruses. The increase of viral infection was favoured also by enhanced specific metabolic activity of single prokaryotic cells. The enhanced viral impact was associated with an alteration of bacterial assemblage composition and a reduction of bacterial diversity. Conversely extremely low pH values affected negatively the viral activity and the virus-prokaryotes interaction, reducing the viral pressure on microbial assemblage. Further studies are needed to investigate the potential impact of global climate changes on future oceans and their biogeochemical processes
Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats
Full text linkThe present study examined the dietary composition of long-snouted seahorse H. guttulatus Cuvier, 1829 in Mar Piccolo of Taranto (Apulia, Italy)using a non-destructive flushing method. To assess differences in the selection of prey among different habitats, adult specimens were collected from both highly complex (Cladophora prolifera and Corallina elongata)and low complex (unvegetated Sandy bottom)habitats. Additionally, samples of benthic fauna were collected from the same habitats and were used to investigate the local availability of potential preys. Results showed significant differences in the diet composition among three studied habitats. Consistently with the results of faunal analysis, gut contents of specimens sampled on C. elongata had higher prey abundance and diversity compared to the other two habitats. Dietary composition of seahorses found in the vegetated habitats was similar, and it was mainly based on Amphipoda and Copepoda. However, small prey (<1 mm)was more consumed on C. elongata than on C. prolifera. On the sandy bottom, H. guttulatus preyed mainly on small crustaceans, but actively selected larger prey (i.e. Galathoidea and Paguroidea). Nematodes were also highly preyed in all habitats, although the high consumption could be possibly attributed to the high abundance and availability of these organisms at the investigated site. H. guttulatus showed a great ability to exploit available resources in the best possible manner among different habitats, acting as a specialist predator. With an aim to understand the use of food resources that are available in the environment, the results of this study could help to propose initiatives directed to the seahorse conservation. Since prey availability does not seem to be a limiting factor in the understanding of variability and consistency of H. guttulatus populations, further studies on other environmental and biological aspects could be useful in the assessment of the conservation status of long-snouted seahorses
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
Ocean Acidification Induces Changes in Virus–Host Relationships in Mediterranean Benthic Ecosystems
No full textAcidified marine systems represent “natural laboratories”, which provide opportunities to investigate the impacts of ocean acidification on different living components, including microbes. Here, we compared the benthic microbial response in four naturally acidified sites within the Southern Tyrrhenian Sea characterized by different acidification sources (i.e., CO2 emissions at Ischia, mixed gases at Panarea and Basiluzzo and acidified freshwater from karst rocks at Presidiana) and pH values. We investigated prokaryotic abundance, activity and biodiversity, viral abundance and prokaryotic infections, along with the biochemical composition of the sediment organic matter. We found that, despite differences in local environmental dynamics, viral life strategies change in acidified conditions from mainly lytic to temperate lifestyles (e.g., chronic infection), also resulting in a lowered impact on prokaryotic communities, which shift towards (chemo)autotrophic assemblages, with lower organic matter consumption. Taken together, these results suggest that ocean acidification exerts a deep control on microbial benthic assemblages, with important feedbacks on ecosystem functioning
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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