1,721,009 research outputs found
Trophic relationships at intrannual spatial and temporal scales of macro and megafauna around a submarine canyon off the Catalonian coast (western Mediterranean)
No full textInfluence of environmental variables on the spatio-temporal dynamics of bentho-pelagic assemblages in the middle slope of the Balearic Basin (NW Mediterranean)
No full textFood web structure of deep-sea macrozooplankton and micronekton off the Catalan slope: Insight from stable isotopes
No full text10 pages, 6 figures, 4 tablesFood web structure of the macroplankton/micronekton fauna on the continental slope of the Catalan Sea (Balearic basin, NW Mediterranean) was investigated using carbon and nitrogen stable isotope tracers on a total of 34 taxa. Samples were collected close to Barcelona, Spain, on the middle slope, at a seasonal scale. Mean δ13C values ranged from −22.1‰ (Salpa maxima) to −16.9‰ (the mysid Eucopia hanseni). Values of δ15N ranged from 2.5‰ (the hyperiid Vibilia armata) to 9.8‰ (the pelagic polychaete Tomopteris sp.). The
stable isotope ratios of this fauna displayed a continuum of values over the δ15N range of 7‰, confirming a wide spectrum of feeding strategies (from filter feeders to predators). High annual mean δ15N values were
found among carnivorous large zooplankton and micronekton, including species that prey on gelatinous plankton (i.e. salps, siphonophores), euphausiids, natantian decapod crustaceans and fish (i.e. myctophids
and stomiiformes). In agreement with the available information on diets of planktonic taxa, the lowest isotope ratios were found for filter feeders (V. armata, S. maxima, the pteropods Cymbulia peroni and Cavolinia inflexa, ostracods and the thaliacean Pyrosoma atlanticum), all of which feed on particulate organic matter. We found three trophic levels in macroplankton/micronekton food webs based on a 15N-enrichment factor of ~2.5‰per level. The range of δ13C was particularly wide among carnivores (−20.7‰ to −16.6‰), suggesting predation
on a variety of prey from gelatinous zooplankton (which displayed more depleted δ13C signatures) to small fishes and decapods. Correlation between δ13C–δ15N was generally weak, likely due to the consumption of different kinds of sinking particles (e.g. marine snow, phytodetritus), some constituted of multiply recycled particulate organic matter (POM). However, higher δ13C–δ15N correlations were observed during winter and spring, periods of water column homogenization, suggesting that the planktonic community assimilates pulses of new production from the photic zone (peaking in January–February). Low correlations were
observed during periods of water column stratification, particularly in summer, when production is especially low, suggesting that in this period macroplankton–micronekton community rely on sources other than
surface primary production such as POM derived from river dischargeThis study was carried out within the framework of the Spanish funded BIOMARE projects (ref. CTM2006-13508-CO2-02/MAR: Identification of BIOmarkers of the anthropogenic impact on MARine communities: an Ecosystemic approach) and ANTROMARE (ref. CTM2009-12214-C02-01/MAR)Peer reviewe
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
Environmental drivers of megafaunal assemblage composition and biomass distribution over mainland and insular slopes of the Balearic Basin (Western Mediterranean)
No full text16 pages, 6 figures, 4 tables, 1 appendixThe influence of mesoscale physical and trophic variables on deep-sea megafauna, a scale of variation often neglected in deep-sea studies, is crucial for understanding their role in the ecosystem. Drivers of megafaunal assemblage composition and biomass distribution have been investigated in two contrasting areas of the Balearic basin in the NW Mediterranean: on the mainland slope (Catalonian coasts) and on the insular slope (North of Mallorca, Balearic Islands). An experimental bottom trawl survey was carried out during summer 2010, at stations in both sub-areas located between 450 and 2200m water depth. Environmental data were collected simultaneously: near-bottom physical parameters, and the elemental and isotopic composition of sediments. Initially, data were analysed along the whole depth gradient, and then assemblages from the two areas were compared. Analysis of the trawls showed the existence of one group associated with the upper slope (US=450-690m), another with the middle slope (MS=1000-1300m) and a third with the lower slope (LS=1400-2200m). Also, significant differences in the assemblage composition were found between mainland and insular slopes at MS. Dominance by different species was evident when the two areas were compared by SIMPER analysis. The greatest fish biomass was recorded in both areas at 1000-1300m, a zone linked to minimum temperature and maximum O2 concentration on the bottom. Near the mainland, fish assemblages were best explained (43% of total variance, DISTLM analysis) by prey availability (gelatinous zooplankton biomass). On the insular slope, trophic webs seemed less complex and were based on vertical input of surface primary production. Decapods, which reached their highest biomass values on the upper slope, were correlated with salinity and temperature in both the areas. However, while hydrographic conditions (temperature and salinity) seemed to be the most important variables over the insular slope, resource availability (gelatinous zooplankton and Calocaris macandreae) predominated and explained 59% of decapod assemblage variation over the mainland slope. Both fish and decapods were linked to net primary production recorded over the mainland 3 months before sampling, while the delay between the input of food from the surface and fish abundance was only 1 month on the insular slope. Our results suggest that trophic relationships over insular slopes probably involve a shorter food chain than over mainland slopes and one that is likely more efficient in terms of energy transfer. © 2013 Elsevier Ltd.This study was carried out within the framework of the Spanish funded ANTROMARE project (ref. CTM2009-12214-C02-01/MAR)Peer Reviewe
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
Distribution and diversity of open-ocean, near-bottom macroplankton in the western Mediterranean: Analysis at different spatio-temporal scales
No full textAppropriate 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
Long-term changes in the composition and diversity of deep-slope megabenthos and trophic webs off Catalonia (western Mediterranean): Are trends related to climatic oscillations?
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