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The impact of hydrological dynamics on cladocera community in a deep sub-alpine lake (L. Iseo): a paleolimnological perspective
No full textLake deposits provide ideal archives to study the past catchment dynamics and the related response of
lake ecosystems. In particular, sediment records deposited over long time periods can provide information
on lake development stages preceding the moment of the most relevant human disturbance, and can help
disentangling and quantifying the lake ecosystem responses to natural variability and human perturbation,
such as climatic and hydrological variation, eutrophication and chemical contamination. Subfossil
Cladocera records allow tracking long-term changes in both bottom-up drivers and top-down regulators
and they particularly respond to alterations in nutrients, temperature and water level. The aim of this work
was to investigated a short sediment core from a deep subalpine lake (Lake Iseo, northern Italy) aiming at
reconstructing the influence of human activities and climate variability on the lake ecosystem. We
compared the sediment records with historical information on major hydrological events during the last
century, and with climate-related limnological data. As already observed in other subalpine lakes, the
sediment records of Lake Iseo suggest that catchment related processes are able to decisively affect the
food web dynamics and the lake functionalities. In particular, we observed that a series of flood events in
the period between the 1970s and 1980s resulted in a decrease in the Cladocera total abundance and a
prevalence of the littoral species over the pelagic one. The decline of the pelagic species has been
attributed to the transport of inorganic material from the catchment area to the lake
A paleolimnological investigation of the impact of catchment dynamics on pelagic communites in a deep south-alpine lake (L. Iseo)
No full textThe emerging issue of microplastics: ongoing investigation in water and sediments of Subalpine lakes
Full text linkWidespreading presence of microplastics in aquatic environments is of increasing ecological concern because of their chemical persistence and their potential effects in biota. Most studies have been focused on marine environments and only a few investigations have been performed on microplastics in freshwater ecosystems. The present work is addressed at identifying the different microplastic polymer types and to characterize their occurrence, features, fate, and the evolution of their abundance in four South-Alpine lakes (Iseo, Idro, Ledro, Garda) in Northern Italy. To achieve this goal, microplastics will be sampled from sediment cores collected from two different locations for each lake. In addition, water samples will be collected at different depth along the water column and analyzed for the presence of microplastics. As these lakes are characterized by different features in relation to watershed extension, hydrological characteristics and human impacts, their study can provide a useful framework to assess the occurrence of microplastics as related to environmental variability. This investigation will provide first insights on the role of lakes as possible “sink” of microplastics, through an accumulation and segregation in deep sediments, or as a “source”, due to a possible preferential distribution in the water column in relation to climate-related turnover patterns that could again bring large amounts of particles to the surface layers. The samples will be analyzed with innovative techniques (Raman spectroscopy and FTIR), which will allow the polymer identification of very small particles. This project will contribute to fill the knowledge gap regarding the abundance and distribution of microplastics in lake ecosystems, and will attempt relating types, occurrence and possible sources of microplastic in the watershed
Cladocera paleocommunity to disentangle the impact of anthropogenic and climatic stressors on a deep subalpine lake ecosystem (Lake Iseo, Italy)
Full text linkIn big lakes with strong anthropogenic pressure, it is usually difficult to disentangle the impacts of climate variability from those driven by eutrophication. The present work aimed at the reconstruction of change in the species distribution and density of subfossil Cladocera in Lake Iseo (Italy) in relation to climate and anthropogenic pressure. We related subfossil Cladocera species composition and density in an 80-cm sediment core collected in the pelagic zone of Lake Iseo to long-term temperature trends and phosphorus concentration inferred by diatoms frustules. The Cladocera remains detected in Lake Iseo sediment reflected the species composition and density of modern pelagic Cladocera assemblages. Cladocera rapidly respond to environmental change, and that climate change combined with eutrophication can induce changes in community composition and
species density. At the beginning of twentieth century, when global warming was not yet so accentuated, the nutrient increase in water resulted as the principal driver in determining the long-term development of plankton communities and pelagic food web structure. Moreover, catchment-related processes may decisively affect both species composition and density of the lake planktonic communities due to the decrease of lake water transparency induced by input of inorganic material from the catchment area to the lake. The paleolimnological investigation, through the combined study of biotic and abiotic factor, allowed clarifying the synergic effects of the most important drivers of change in lake ecosystems, suggesting that climatic factors should be considered with nutrient availability as determinant element in controlling the temporal development of plankton communities and pelagic food web structure
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
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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