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Competition between a planktonic diatom and a dinoflagellate during enclosure experiments in a mountain lake
No full textLake Tovel (Trentino, Brenta Dolomites, NE Italy) was renowned for red blooms due to the dinoflagellate Glenodinium sanguineum. These blooms suddenly ceased in 1964. Responses of the summer phytoplankton communities to nutrient enrichments, analysed experimentally in enclosures, identified phosphorus as the factor limiting both G. sanguineum and a dominant Fragilaria tenera. Competitive interactions suggested that the dinoflagellates were favoured by higher temperatures, whereas the diatoms were limited by silica reduction. The ratio between the biovolumes of the two algae was an important parameter for predicting which species would benefit from the phosphorus additions and outcompete the other one under the experimental condition
Blooms of the dinoflagellate Glenodinium sanguineum obtained during enclosure experiments in Lake Tovel (N. Italy)
Full text linkFreshwater red tides due to dinoflagellates are less common than their marine analogues, which are usually a serious problem and can even be toxic. This was not the case for Lake Tovel in the Adamello-Brenta Natural Park (Southern Alps, Italy), where the dinoflagellate Glenodinium sanguineum Marchesoni accumulated carotenoids (astaxanthin-like compound) and caused a spectacular and regular "summer reddening", which suddenly ceased in 1964. Today Lake Tovel is a temperate, meromictic (with dimictic mixolimnion), oligotrophic mountain lake, characterised by marked water level fluctuations. G. sanguineum is still present in the lake, although with markedly lower densities in comparison to the pre-1965 period. Enclosure studies were carried out to identify the main factors regulating the blooms. In 1998, by means of phosphorus enrichments, it was possible to obtain a marked increase in numbers of G. sanguineum. Phosphorus additions in similar enclosures in 1999, when weather conditions during the summer were not optimal (mostly cloudy with frequent rainfalls), did not have the same effect, since species known to thrive in spring or under icecover developed. In summer 2000, by attenuating light in one of the enclosures, it was shown that irradiance conditions strongly interacted with phosphorus availability in determining the species that dominated the phytoplankton. In summer 2001, G. sanguineum increased again in the enclosure enriched with phosphorus. Nitrogen was observed to become a limiting factor only in conditions forced by phosphorus additions. From the first four years of in situ experiments, we concluded that phosphorus and light conditions were among the key factors controlling the proliferation and the dominance of G. sanguineum
Ecological and taxonomic observations on the flagellate algae characterising four years of enclosure experiments in Lake Tovel (Southern Alps)
No full textLake Tovel (Italian Alps, Brenta Dolomites, 1178 m a.s.l.), with a dimictic mixolimnion, is a meromictic and oligotrophic mountain lake, once notorious for the summer reddening of its waters due to dinoflagellate blooms that ceased suddenly in 1964. Since 1997 the Museo Tridentino di Scienze Naturali has been carrying out in situ experiments in order to understand the factors regulating the blooms. Experiments were carried out in different types of enclosures to test the reaction of phytoplankton to phosphorus enrichment and light reduction, with special reference to Glenodinium sanguineum Marchesoni, the dinoflagellate responsible for the reddening. The aim of the present contribution is to study the ecology of other flagellate algae typical of Lake Tovel, by analysing the data from the enclosure experiments. Particular attention is given to competition for resources, the comparison with G. sanguineum and some interesting taxonomic observations. The four flagellate taxa selected for this investigation were Gymnodinium uberrimum (Allman) Kofoid & Swezy, Dinobryon cf. sociale var. americana (Brunnthaler) Bachmann, Campylomonas sp. and Tetraselmis sp. Number of individuals and biovolume calculated for each taxon during the experiments were statistically related to NO3-N and TP concentrations, water temperature, pH and oxygen saturation. A prompt and positive response to P-enrichment was found in all experiments for both G. sanguineum and G. uberrimum. However, the first taxon showed a pronounced development only when nutrients were coupled with high light intensities, while the latter appeared to be a better competitor in low light intensities and low water temperature. The behaviour of Tetraselmis sp. was similar to that of G. sanguineum, while the development pattern of Campylomonas sp. was similar to that of G. uberrimum. D. sociale did not show a clear relationship either to nutrient enrichment or weather conditions
Contact and photocontact dermatitis due to benzydamine hydrochloride
No full textNo abstract availabl
On-line identification of secondary metabolites in freshwater microalgae and cyanobacteria by combined liquid chromatography-photodiode array detection-mass spectrometric techniques
No full textThe analysis and identification of a wide range of secondary metabolites biosynthesized by different algal taxa and cyanobacteria has been performed through a selective and sensitive methodology, mainly based on reversed-phase HPLC coupled both to UV photodiode array detection and to atmospheric pressure mass spectrometric techniques (HPLC-DAD-APIMS). Results are reported here with special attention to the analyses carried out both on the natural phytoplankton (mixed populations) of Lake Tovel (Northern Italy, Brenta Dolomites) and on enclosure-produced biomass of the dinoflagellate Glenodinium sanguineum Marchesoni (1941). This analytical procedure might represent a powerful tool for the fast screening of the taxonomic composition (broad groups, e.g. divisions) of natural mixed populations of phytoplankton, by providing a reliable distribution of accessory pigments extracted from microalgae, such as carotenoids and chlorophyll derivatives. Furthermore, we showed that in the same chromatographic analysis other classes of natural products, such as galactolipids, alkaloids, sterols and mycosporine-like amino acids, can be detected by using combined optical and mass spectrometric techniques. These metabolites represent distinctive biochemical signatures, sometimes even at the species level. © 2005 Elsevier B.V. All rights reserved
Technical losses assessment in distribution systems with reduced measurement capabilities
No full textIn the recent years, the electricity Regulators want to reduce the energy cost and to raise the energy efficiency by curtailing the energy losses, particularly in the MV and LV distribution networks. The definition of an adequate methodology for the calculation of the energy losses in the distribution system is crucial for both the Regulator and the Distribution Companies (DISCOs). The assessment of the energy losses in distribution systems with reduced measurement capabilities (fast developing countries) is usually performed by resorting to simplified methods of calculation or to the simple difference between purchased and billed energies. This approach may provide too imprecise or inaccurate results. Better accuracy can be achieved with the methodology illustrated in this paper
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
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