1,720,993 research outputs found
Molecular identification of Ostreopsis species in the Mediterranean coastal waters using fluorescent oligonucleotide probes.
No full textTecniche molecolari di PCR applicate all’identificazione di fitoplancton potenzialmente tossico in aree costiere dell’Adriatico settentrionale
No full textNew potential expansion of toxic tropical marine micro-organisms in relation to oceanic climate change
No full textBioavailability of different chemical forms of dissolved silica can affect marine diatom growth
Full text linkIn this study, we demonstrate that dissolved silica obtained from mineral (crystalline quartz), biogenic amorphous (diatomaceous earth) and artificial amorphous sources (Aerosil) influence the growth rate of two marine diatoms, Chaetoceros sp. and Skeletonema marinoi. Diatoms were reared in four different experimental conditions in artificial seawater containing either dissolved silica previously obtained through dissolution of the mineral crystalline quartz or
two amorphous substrates, biogenic diatomaceous earth or artificial Aerosil silica. Sodium metasilicate was used as control. When the silica in the different media reached concentrations higher than 107 lM, particles were eliminated by filtration and the diatom cells were inoculated. Maximum cell density, growth and silica assimilation rates of both species in the presence of dissolved silica derived from crystalline quartz and metasilicate were higher than those
obtained with the other silica sources. These results are discussed against the background of previous geochemical studies that have shown that silica–water interactions are strictly dependent on the silica polymorphs involved and on the ionic composition of the solution. Our results demonstrate that the soluble silicon compounds generated in seawater by crystalline sources are highly bioavailable
compared with those generated by biogenic and amorphous materials.
These findings are potentially of considerable ecological importance and may contribute to clarifying anomalous spatial and temporal distributions of siliceous organisms with respect to the presence of lithogenic or biogenic silica sources in marine environments
Monitoring toxic Ostreopsis cf. ovata in recreational waters using a qPCR assay.
Full text linkOstreopsis sp. is a toxic marine benthic dinoflagellate that causes high biomass blooms, posing a threat to
human health, marine biota and aquaculture activities, and negatively impacting coastal seawater quality.
Species-specific identification and enumeration is fundamental because it can allow the implementation
of all the necessary preventive measures to properly manage Ostreopsis spp. bloom events in
recreational waters and aquaculture farms. The aim of this study was to apply a rapid and sensitive qPCR
method to quantify Ostreopsis cf. ovata abundance in environmental samples collected from Mediterranean
coastal sites and to develop site-specific environmental standard curves. Similar PCR efficiencies
of plasmid and environmental standard curves allowed us to estimate the LSU rDNA copy number per
cell. Moreover, we assessed the effectiveness of mitochondrial COI and cob genes as alternative molecular
markers to ribosomal genes in qPCR assays for Ostreopsis spp. quantification
Monitoring toxic microalga Ostreopsis (Dinoflagellate) species in coastal waters of the Mediterranean Sea using molecular PCR-based assay combined with light microscopy
Full text linkA molecular PCR-based assay was developed and applied to macrophyte and seawater samples containing mixed microphytobenthic and phytoplanktonic assemblages, respectively, in order to detect toxic Ostreopsis species in Mediterranean Sea. The specificity and sensitivity of the molecular PCR assay were assessed with both plasmidic and genomic DNA of the target genus or species using taxon-specific primers in the presence of background macrophyte DNA. The PCR molecular technique allowed rapid detection of the Ostreopsis cells, even at abundances undetectable within the resolution limit of the microscopy technique. Species-specific identification of Ostreopsis was determined only by PCR-based assay, due to the inherent difficulty of morphological identification in field samples. In the monitoring of the toxic Ostreopsis blooms PCR-based methods proved to be effective tools complementary to microscopy for rapid and specific detection of Ostreopsis and other toxic dinoflagellates in marine coastal environments
Monitoring of HAB species in the Mediterranean Sea through molecular methods
Full text linkA qualitative and semi-quantitative polymerase chain reaction (PCR)-based assay was developed for the detection of several potentially Harmful Algal Bloom (HAB) species and genera belonging to Dinophyceae, Bacillariophyceae and Raphydophyceae. Oligonucleotide primers were designed based on Internal Transcribed Spacer (ITS)-5.8S ribosomal DNA (rDNA) sequences available in public database or identified in this study. The specificity and sensitivity of the PCR assay were validated using clonal cultures and then natural seawater samples, as well as the known copy number of plasmids containing the target ITS-5.8S rDNA regions. A filter system for collecting mixed phytoplankton cells coupled to a target species-specific PCR assay was performed on spatial and temporal series of net and surface seawater samples during coastal water monitoring carried out in several localities of the Mediterranean Sea. The application of PCR allowed a rapid detection of various genera and species-specific potential HAB taxa in all examined natural samples. Qualitative and semi-quantitative PCR results obtained from field samples were compared with microscopic [light microscope (LM)] examinations. The two methods gave comparable results, and the molecular assay was able to detect HAB target cells at concentrations not detectable by microscopy or those of uncertain identity. The highest values of positive detection of potential HAB taxon presence obtained by PCR assay compared with the microscopic examination ranged from 67 to 8.0%
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
- …
