1,721,001 research outputs found
Macro-litter ingestion in deep-water habitats. Is an underestimation occurring?
No full textMarine litter affects marine organisms, posing threats to biodiversity conservation and to ecosystem structure and functioning. Providing a suitable assessment of marine litter effects on marine life through bioindicator species is crucial to drive an effective waste management policy. However, to date no standardized tool has been developed to describe and monitor the impact of marine macro-litter on marine life within deep-water habitats. Modifying the protocol proposed to monitor macro-litter ingestion by the loggerhead sea turtle Caretta caretta, we perform a preliminary investigation on the suitability of different elasmobranch species for monitoring macro-litter ingestion in deep-sea. A total of 122 specimens representing 7 elasmobranch species were collected and examined. External visual inspections documented no clear evidences of disease due to marine litter entanglement. A total of 7 ingested litter items were found in the stomach or in the esophagus of 6 specimens of 4 different species (frequency of occurrence = 4.9%), with a maximum number of 2 items per specimen. No litter items were found in the intestinal contents, as well as no evidence of gastrointestinal blockages due to litter items were detected. The low number of collected litter items suggests that the number of samples required is too large for a feasible monitoring program. Moreover, we observed that the anatomy of the intestinal spiral valve may represent an obstacle to the transit of macro-litter items, which could be spontaneously regurgitated as it happens in the selective elimination of undigested remains, such as bones and scales. Therefore, macro-litter retention time in the gastrointestinal tract of elasmobranchs could be brief and shorter than retention time of food. This may lead to an underestimation of macro-litter ingestion frequency by deep-water elasmobranchs. This study reports the first evidence of plastic ingestion by the kitefin shark Dalatias licha
A comparison of new and conventional methods for isolating microplastics ingested by fish
No full textIn recent years an increasing number of techniques have been developed to detect microplastics ingested by biota. In this study we propose a new simple and rapid method of microplastics extraction in comparison with methods commonly used. The new procedure consists of: fish gastrointestinal tract extraction; organic matter digestion with a mixture of HNO3 5% and H2O215%; vacuum pump filtration through a fiber glass membrane; microplastics identification under stereomicroscope. Six types of polymers (nylon, polypropylene, polyethylene, polystyrene, polyvinylchloride, polyethylene terephthalate) were analyzed before and after the inclusion in different mixtures of H2O2 and HNO3 in order to compare the potential plastic degradation among the tested solutions. Changes in plastic items surface, colors and shape were evaluated with imaging software for microscopy (ZEN 2011 SP1) and processing software (ImageJ), before and after the treatments. The Fourier Transformed Infra-Red Spectrometry analyses (FT-IR) were used to evaluate the integrity of polymers structure. An homogenized pool, including gastro intestinal tissue and contents (from the esophagus to the cloacae), of 30 Scomber japonicus (Houttuyn, 1782), was subdivided in aliquots of around 9 grams each. The proposed procedure for biological material removing (adding 10 ml of H2O2 15% and HNO3 5% solution for one gram of tissue at 40 °C) was compared with two common methods, one using an oxidant agent as H2O2 15% at 50 °C, the other a strong base as KOH 10% at 60 °C . Samples were processed using 10 aliquots for each protocol. The results showed an efficiency over 95% on digested biological materials for the proposed procedure. Our results are comparable with those obtained using KOH protocol but with a clearer filtering membrane and an higher efficiency with respect to H2O2 15% alone
Food preference determines the best suitable digestion protocol for analysing microplastic ingestion by fish
No full textMicroplastic presence in the marine environment has generated considerable concern. Many procedures for microplastics detection in fish gastrointestinal tract have been recently developed. In this study, we compared efficiencies of two common procedures applied for the digestion of organic matter (10% KOH; 15% H2O2) with a new proposal (mixture of 5% HNO3 and 15% H2O2). We considered ecological diversity among species and differences in their diet compositions as factors that could affect the efficiency and feasibility of analytical approaches. Our aim was to understand whether either one of the three protocols might be suitable for all species or it might be more advisable to select a method according to the gut content determined by different food preferences. The results showed that the trophic level and feeding habits should be considered for protocol selection. Finally, we applied the best protocols on samples from the Tyrrhenian sea
Microplastics ingestion by deep-water catsharks Galeus melastomus and Scyliorhinus canicula (Chondrichthyes) in the Tyrrhenian sea (Western Mediterranean Sea)
No full textNowadays plastic debris must be considered a ubiquitous element of marine ecosystems, distributed both in shallow and deep-water. Different diet studies suggest that shark and rays could be threatened by plastic ingestion. Blackmouth catshark, Galeus melastomus (Rafinesque, 1810) and lesser-spotted catshark, Scyliorhinus canicula (Linnaeus, 1758) are two abundant deep-water elasmobranchs, both opportunistic scavengers, whose feeding habits have been widely studied in overlaps and differences. The aim of our study is to verify any differences in frequency of plastic ingestion by the two species and to evaluate possible incidence according to the intra-specific variables. Samples result from a by-catch of professional fishing boat armed with trawl net for Giant red shrimps capture at depths between 400 m and 500 m. Morpho-anatomical data (total length, total weight, sex, maturity stage, weight of liver and gonads) were recorded for each individual. Stomach and intestinal contents were weighed before incubating separately in a 10% KOH digestive solution at 60 °C overnight, to remove biogenic material and identify plastic debris using a stereomicroscope. Nature of suspected items was determined using Fourier Transformed Infra-Red spectrometry (FT-IR). Preliminary results confirm that plastic ingestion occurs in both species and filaments-like are the most frequent items, without significant differences in the two catsharks. However, there is a greater variability in shape of plastics (sphere, fragment, film) ingested by G. melastomus than S. canicula. This probably reflects differences in feeding habits of the two species. The detection of plastics in the final part of the gastro-intestinal tract of both species seems to suggest that these animals can expel the plastics with the feces and no forms of gastric blockage have been observed. Studies are in progress to verify the magnitude of the observed differences between the two species and to better investigate the phenomenon
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
Random or not? Comparing microplastic ingestion and preys in Scomber colias and Trachurus trachurus
No full textMicroplastics represent a rising threat to marine biota. As the fishing industry is a fundamental source of sustenance for human beings, microplastic ingestion by fish deserves appropriate attention. Despite previous studies suggest that the feeding behavior of different fish species may affect the occurrence and the diversity of ingested microplastic types, little is known about the selection mechanisms that determine the pathways of microplastics through the food webs. In this study we combine the characterization of ingested microplastics with the analysis of the diet composition of two pelagic fish species, namely the Atlantic chub mackerel Scomber colias and the Atlantic horse mackerel Trachurus trachurus. Samples were collected during a single fishing trip carried out in spring 2021 off Anzio coast (Tyrrhenian Sea, Western Mediterranean). After the dissection, samples were divided into two subgroups to be analyzed for diet composition and microplastic analysis, respectively. Gastrointestinal tracts to be analyzed for microplastics underwent alkaline digestion (10% KOH) to degrade the organic matter. Then, solutions were filtered on glass microfiber membranes and subsequently observed under a stereomicroscope. Microplastics were characterized by shape, color, and polymer composition. Stomach contents for diet analysis were observed under a microscope and preys were identified at the lower taxonomical level. The preliminary analyses show that T. trachurus makes an active selection of fastmoving preys (mostly Teleosts) and ingest almost only threadlike microplastics, such as fibers and filaments. In contrast, the high frequency of Thaliaceans in S. colias reveals a more planktivorous behavior, which is associated to the ingestion of a wider variety of microplastic types (including also film, fragment and foam). These results seem to suggest that the microplastic ingestion patterns observed in the two examined species could be linked to the existing differences between their prey searching modalities
Is the Loggerhead Caretta caretta a good indicator of plastic ingestion also at local scale?
No full textThe European Commission drafted the 2008/56/EC Marine Strategy Framework Directive with the aim to achieve a Good Environmental Status (GES). In 2011 Italy promoted the Loggerhead sea turtle (Caretta caretta, Linnaeus 1758) as target species for monitoring the amount and composition of litter ingested by marine animals and then it has been accepted
among MSFD Indicators and under the UNEP/MAP Barcelona Convention ecological objective, at sub-regional level. 120 death loggerhead CCL ranging from 21 to 80 cm (average = 54.9 cm) have been collected stranded or by-catch along Latium and Sardinian coasts, Italy (Western Mediterranean sub-Region). Plastic ingestion has been detected with a frequency of occurrence FO=54.2%. In total, 106.138 g (dry mass) and 1103 items (abundance) of marine litter were collected with an average value of 0.892 ± 0.196 g and 9.27 ± 1.95 items. Among the impacted turtles, parts of plastic bags and other sheet fragments (USE she) were the main categories in terms of abundance (17.23 ± 3.35 items). At local level, FO%, dry mass and number of items between the two areas (Latium: FO = 79.0%, average g= 1.553 ± 0.354, average n Items = 14.76 ± 3.53; Sardinia: FO = 27.6% average g=0.173 ± 0.059, average n Items= 3.30 ± 0.95) showed significant differences and groups structure was confirmed by nonhierarchical cluster analysis. This study shows that, even if sea turtles are migratory species and marine litter move according to the current and tide, the loggerhead can give information on plastic pollution also at local scale
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
Microplastic detection and Lagrangian modelling in the Tyrrhenian Sea
No full textIn recent years the presence of microplastic (MP) in oceans is getting more and more attention due to its impacts on these environments. A major concern is represented by closed and densely populated basins, like the Mediterranean Sea. In this work, an assessment of MP concentrations in the Tyrrhenian Sea, a sub-basin of the Mediterranean Sea, is performed by means of numerical simulations. A Lagrangian stochastic model of dispersion, which requires hydrodynamic fields and MP sources as inputs, is employed. The hydrodynamic fields are supplied by the Copernicus Marine Environment Monitoring Service (CMEMS), while the MP sources are estimated by means of a novel method based on the population density. The results agree well with field data derived from Goletta Verde sampling campaign and highlight the importance of a correct estimation of the sources. Both the numerical results and field data show the presence of high polluted areas
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