1,721,009 research outputs found
Taxonomic and functional trait variation along a gradient of ammonium contamination in the hyporheic zone of a Mediterranean stream
Full text linkAmmonium has detrimental effects on the survival and physiology of freshwater invertebrates, however, the effects of ammonium on the functionality of hyporheic invertebrate assemblages have never been investigated. In this study, we applied a mixed (taxonomy- and trait-based) approach to explore the taxonomic and functional trait variation along a gradient of ammonium contamination in the hyporheic zone of a Mediterranean stream. We analysed fifty-one trait modalities of thirty-eight invertebrate taxa. We tested a priori hypotheses on the functional traits that should be affected. We observed a severe erosion of taxonomic and functional diversity with the loss of 12 taxa and 11 trait modalities related to size and body form, fecundity and reproduction, resistance forms and respiration, diet, locomotion and feeding habits. The effect on taxonomic and trait modality abundances was also relevant; in particular, the decrease in detritivores seemed to have led to a low content in dissolved organic matter. Synergic detrimental effects of ammonium and the summer season were also observed. Despite some uncertainties, we found out that the mixed approach responded consistently along a gradient of ammonium contamination. Since functional traits link community organization to ecosystem goods and services, the results of our study could be prodromal to the inclusion of ammonium as indicator of functional stress in a health index of hyporheic zones in Mediterranean rivers
Ecological risk assessment of pesticide mixtures in the alluvial aquifers of central Italy: Toward more realistic scenarios for risk mitigation
No full textGroundwater biodiversity in a chemoautotrophic cave ecosystem: how geochemistry regulates microcrustacean community structure
No full textThe Frasassi cave system in central Italy hosts one of the few known examples of a groundwater metazoan community that is supported by sulfur-based lithoautotrophic microbes. Despite the challenging conditions represented by high concentrations of H2S and low concentrations of O2, this cave system is home to many invertebrate species. Here, we analyzed the copepods inhabiting sulfidic lakes and non-sulfidic dripping pools in order to investigate how environmental conditions in sulfidic waters regulate the spatial distribution of the cave microcrustacean community over time. We also sampled copepod assemblages of sulfidic lakes under conditions of both high and low H2S concentration. Cluster analysis and canonical correspondence analysis separated the copepod assemblages inhabiting dripping pools from those of sulfidic lakes. H2S concentration, pH and O2 concentration were identified as the main factors regulating community structure. These results indicate that the distribution of groundwater copepods within the cave system is ecologically and spatially structured. Sulfidic lakes showed lower Simpson dominance, higher Shannon diversity and higher Pielou equitability at higher H2S concentrations. The complex community structure of the copepods of the Frasassi cave system suggests that a chemosynthetically produced food source facilitated the colonization of stygobionts in sulfidic groundwater due to their tolerance to the environmental conditions
The impact of nitrate on the groundwater assemblages of European unconsolidated aquifers is likely less severe than expected
No full textIn this study, we analyzed the structure of the stygobiotic copepod assemblages of an unconsolidated European aquifer (VO), in southern Italy, that has been subject to persistent nitrate contamination for over 15 years. To this end, we monitored 25 bores where groundwater was contaminated only by nitrate, and no other chemical pollutants were reported as being above detection limits from 2009 to 2014. We monitored these bores three times, namely in autumn 2014 and in spring and autumn 2015. We expected that the chronic exposure to high nitrate concentrations had a significant and evident impact on the stygobiotic copepod assemblages. Unexpectedly, the assemblages were highly diversified. The stygobiotic species richness (SSR) accounted 17 species, a value that exceeded the European mean value (SSR = 12 species). However, the species density was only 0.6 species/km2, lower than the European mean value (= 1.6 species/km2). Moreover, the juvenile copepods were numerically less abundant than the adults and the biomass-abundance model showed signs of alteration of the structure of the copepod assemblages. This study highlighted that (i) nitrates, even at high concentrations, probably have a less severe impact on groundwater assemblages of unconsolidated aquifers than expected and (ii) the analysis of population traits and biomasses can detect signs of alteration of these assemblages that would, otherwise, not be visible from the analysis of the sole species richness and abundances
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
Trapped in the web of water : groundwater-fed springs are island-like ecosystems for the meiofauna
Full text linkWe investigated whether the equilibrium theory of island biogeography (ETIB) can be applied to the meiofauna of groundwater-fed springs. We tested whether copepod species richness was related with spring area, discharge, and elevation. Additionally, five hypotheses are tested based on species distribution patterns, dispersal ability, and life-history characteristics of several guilds (stygobiotic, nonstygobiotic, cold stenotherm, and noncold stenotherm species). Thirty springs in the central Apennines (Italy) were considered. A multimodel selection procedure was applied to select best-fit models using both ordinary least-squares regressions and autoregressive models. Mantel tests were used to investigate the impact of spatial autocorrelation in determining interspring similarity (ßsor), pure turnover (ßsim), intersite nestedness (ßnest = ßsor − ßsim), and matrix nestedness (measured using NODF and other metrics). Explicit consideration of spatial correlations reduced the importance of predictors of overall species richness, noncold stenotherm species (both negatively affected by elevation), cold stenotherm species, and nonstygobiotic species, but increased the importance of area for the stygobiotic species. We detected nested patterns in all cases, except for the stygobites. Interspring distances were positively correlated with ßsor and ßnest (but not with ßsim) for the entire data set and for nonstygobiotic, cold stenotherm, and noncold stenotherm species. In the case of stygobites, interspring geographical distances were marginally correlated with ßsor and no correlation was found for ßsim and ßnest. We found support for ETIB predictions about species richness, which was positively influenced by area and negatively by elevation (which expresses the size of source of immigrants). Low turnover and high nestedness are consistent with an equilibrium scenario mainly regulated by immigration and extinction. Stygobites, which include many distributional and evolutionary relicts, have a low capability to disperse through the aquifers and tend to be mainly confined to the springs where they drifted out and were trapped by springbed sediments.AQUALIFE project funded by the European Community (LIFE12 BIO/IT/000231 AQUALIFE)info:eu-repo/semantics/publishedVersio
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
Groundwater drift monitoring as a tool to assess the spatial distribution of groundwater species into karst aquifers
No full textGroundwater drift collected continuously at perennial outlets of karst aquifers has been examined for its potential in assessing the spatial distribution of the resident species. To this end, we have continuously monitored the groundwater drifted at the Mazzoccolo spring (Western Aurunci karst aquifer, Central Italy) over 2 years. Concurrently to the biological monitoring, major ion geochemistry and turbidity were investigated on the same schedule. We found that the hydrochemistry did not govern the distribution pattern of the dominant taxon (Copepoda) into the Western Aurunci aquifer. In contrast, copepod drift showed clear differences in the number of individuals between the high and low water periods because of the âpiston effect,â which is very frequent in karst and fractured aquifers due to recharge from rainfalls. According to the results of this study, groundwater species do not inhabit all sectors of a karst aquifer. They avoid the fast-flowing conduits where groundwater rapidly flows, while colonizing the more inertial aquifer sectors, such as the slow-flowing conduits
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