1,720,985 research outputs found
A new sustainable formulated feed based on discards from food industries for rearing the sea urchin Paracentrotus lividus (Lmk)
Full text linkDuring a 18‐week experiment in a sea‐based system, Paracentrotus lividus was fed
with two formulations of a new sustainable feed whose main ingredients were food
farming discards, mostly outermost lettuce leaves, in different percentage. Egg white
was added as protein source and binder, and a little amount of commercial fish feed
was added as lipid source. At the end of the experiment, a high survival rate (>80%)
and an increase in test diameter (22%), total weight (130%), gonad weight (240%) and
gonad index expressed as size‐adjusted gonad weight (288%) were recorded. Gonads
achieved a good colour and high levels of essential and polyunsaturated fatty acids,
hence representing a commercially valuable product. Comparing the two feed formulations,
the one with the lower lettuce content (57% vs. 67%) led to the best product
quality, in terms of gonad features (gonad index and colour) and content of essential
fatty acids. In order to move towards a higher sustainability of the aquaculture sector,
this study proposes a low‐cost feed, produced with cheap and sustainable ingredients
such as food farming discards
Co-existing with the alien: evidence for environmental control on trophic interactions between a native (Atherina boyeri) and a non-indigenous fish species (Gambusia holbrooki) in a Mediterranean coastal ecosystem
Full text linkBiological invasions are a widespread problem worldwide, as invasive non-indigenous species (NIS) may affect native populations through direct (e. g., predation) or indirect (e.g., competition) trophic interactions, leading to changes in the food web structure. The trophic relationships of the invasive eastern mosquitofish Gambusia holbrooki and the native big-scale sand smelt Atherina boyeri coexisting in three Mediterranean coastal ponds characterized by different trophic statuses (from oligotrophic to hypereutrophic) were assessed in spring through isotopic niche analysis and Bayesian mixing models. The two fish relied on the distinctive trophic pathways in the different ponds, with the evidence of minimal interspecific niche overlap indicating site-specific niche divergence mechanisms. In more detail, under hypereutrophic and mesotrophic conditions, the two species occupied different trophic positions but relying on a single trophic pathway, whereas, under oligotrophic conditions, both occupied a similar trophic position but belonging to distinct trophic pathways. Furthermore, the invaders showed the widest niche breadth while the native species showed a niche compression and displacement in the ponds at a higher trophic status compared to the oligotrophic pond. We argue that this may be the result of an asymmetric competition arising between the two species because of the higher competitive ability of G. holbrooki and may have been further shaped by the trophic status of the ponds, through a conjoint effect of prey availability and habitat complexity. While the high trophic plasticity and adaptability of both species to different environmental features and resource availability may have favored their coexistence through site-specific mechanisms of niche segregation, we provide also empirical evidence of the importance of environmental control in invaded food webs, calling for greater attention to this aspect in future studies
Ecological implications of restoring degraded marine areas using Posidonia oceanica: assessment of plant contamination and fish fauna recovery
No full textThe potential of ecological restoration to re-establish ecosystem structure and function is globally recognised. However, the ecological implications of restoring polluted sites are rarely considered in the assessment of trajectories and recovery processes. Here we present two case studies of restoration of marine coastal areas carried out by transplanting the Mediterranean seagrass Posidonia oceanica from donor meadows to polluted marine areas with the aim of assessing, within six months from transplant: (i) trace element (TE) accumulation in P. oceanica in response to environmental contamination; (ii) fish fauna recovery. We found increased Cr, Cu and Hg accumulation in roots and As in leaves of transplanted plants, confirming that P. oceanica may act as a sink, sequestering TEs and potentially decreasing their availability, but also opening questions about the potential risk of remobilising buried contaminants. At the same time, fish assemblages showed signs of rapid recovery in both areas, i.e., an increase in species richness, abundance, and diversity from the first month after transplantation, indicating a rapid improvement in habitat provision function. Although the amount of TEs potentially transferable from P. oceanica to the ecosystem seems to be low in the study areas, further investigations including cost-benefit assessments of restoring polluted sites by transplanting seagrasses would improve current knowledge in support of efficient ecosystem-based coastal biodiversity management and conservation
Combined exposure to CO2 and H2S significantly reduces the performance of the Mediterranean seagrass Posidonia oceanica: Evidence from a volcanic vent
Full text linkAlthough seagrasses are expected to thrive in future acidified oceans by overcoming low CO2 diffusion into
plant tissues, the co-occurrence of environmental stressors may affect their growth. Volcanic CO2 vents are
often associated with toxic gases and metal-rich fluids representing ideal sites to assess the effects of multiple
stressors. We evaluated the response of Posidonia oceanica growing near shallow CO2 vents characterized by H2S
spill-out by comparing meadow structure and phenology to an area with no gas emissions. Seagrass descriptors
at meadow, shoot and leaf level indicated that P. oceanica experienced stressful conditions at the vent area, in
clear contrast to the flourishing features of P. oceanica previously described at CO2 vents with no evidence of toxic inputs. Furthermore, the reduction in both leaf δ34S and growth at the vent area indicates that sulfide
intrusion occurs and affects seagrass growth performance, dampening the expected beneficial effects of high
CO2 levels
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
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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