1,720,960 research outputs found
Diatoms as bioindicators for health assessments of ephemeral freshwater ecosystems: A comprehensive review
No full textEphemeral waters (EW) are sensitive and vulnerable ecosystems that, although the numerous ecosystem services provided, are poorly investigated and properly managed. Diatoms represent an important biological model largely used in aquatic permanent habitats but underused in ephemeral waters. The aim of this review is to address the knowledge gap, examining the current state of knowledge regarding the health of EW, with a focus on diatoms as bioindicators, specially (i) presenting research trends on EW ecosystem types investigated (ii) analysing the methodological approach, (iii) providing the influence of abiotic factors on the diatom assemblages in EW. A bibliographic search yielded a total of 512 papers. After removing duplicate records, 118 were eliminated. The screening of abstracts resulted in the selection of 48 articles on diatoms and EW since 1982. To avoid discrepancy between terminology we decided to classify the EW found in 3 different categories: Intermittent Running Waters (IRW: rivers, streams, creek, springs), Temporary Large Wetlands (TLW: wetlands, lakes, lagoons) and Temporary Small Waters (TSW: ponds, pools, ventaroles, ditches, thermal waters, troughs, pans). Studies are reported in all continents including Antarctic. IRW are the most investigated ecosystem (n = 683), followed by TSW (239) and TLW (96). Furthermore, studies were mainly conducted on sites located below 1000 m a.s.l. of altitude (n = 27). Studies mainly focus on epilithic diatoms (52 %). Electrical conductivity (80 %), pH (77 %) and water temperature (75 %) are the principal physical-chemical parameters considered. Moreover, electrical conductivity, pH, temperature, nitrate and nitrite resulted the best diatom community drivers. Future research is encouraged (1) to achieve a standardised protocol for monitoring EW using diatoms, (2) to focus on conservation projects for high-altitude temporary waters, and (3) to investigate the main driving forces influencing diatom diversity on EW
New ecological frontiers in the plastisphere: Diatoms and macroinvertebrates turnover assessment by a traits-based approach
No full textTo date, there are very few studies regarding the colonization of artificial substrates in wetlands by macroinvertebrates and diatoms and even fewer are the studies in Italy that take into consideration the diatomic guilds and the biological and ecological traits proposed in literature. Wetlands are at the forefront through the most delicate and threatened freshwater ecosystems. In this study, we want to evaluate the colonization capacity of plastics of diatoms and macroinvertebrates and characterize the diatomic and macroinvertebrate communities using a “traits-based” approach focusing on the colonization of virgin substrates made of polystyrene and polyethylene terephthalate. The study was conducted within the ‘Torre Flavia wetland Special Protection Area’ a protected wetland area in Central Italy. The study was conducted from November 2019 to August 2020. The results obtained in this study show a tendency of diatom species to colonize artificial plastic supports placed in lentic environments without differences related to the plastic type and water depth. There is also a greater number of species belonging to the “Motile” guild, endowed with a high motility that they exploit to search for more ecologically suitable habitats for settlement. Macroinvertebrates, prefer settlement on polystyrene supports, those on the surface, probably due to the anoxic conditions present on the bottom and the physical structure of the polystyrene that provides shelter to many animal taxa. The analysis on traits highlighted the establishment of an ecologically diverse community mainly formed by univoltine organisms, with dimensions between 5 and 20 mm, predators, choppers and scrapers feeding on plant organisms and animals, but without the formation of a clear ecological system, that is, without evidence of ecological relationships established between two or more taxa. Our research can contribute to underline the ecological complexity of biota inhabiting plastic litter in freshwaters and the implications for plastic-impacted ecosystems biodiversity enrichment
Diatom and macroinvertebrate communities dynamic: A co-occurrence pattern analysis on plastic substrates
No full textWetlands are habitats that provide numerous ecosystem services, but are often understudied and threatened by anthropogenic pollution, particularly plastic pollution. Macroplastics are a significant component of plastic litter that have high biological impacts but are often understudied. Previous studies have highlighted negative impacts on biota, but there is a lack of information about the communities of micro and macro organisms that settle on macroplastic litter. In this context, we investigated the colonization patterns and community structures of di-atoms and macroinvertebrates on virgin substrates composed of two different plastic polymers, polystyrene and polyethylene terephthalate, located at two different depths in a protected wetland in Central Italy over a period of 10 months. The results show that diatom community is not highly structured by competitive forces and ag-gregation patterns emerges. In contrast, macroinvertebrate community appears to be randomly structured, without the presence of patterns following specific assembly rules. Randomness in macroinvertebrates assem-blages could highlight the presence of different niches available for settlement of different taxa. Combined matrix analyses show that diatoms and macroinvertebrates co-occur, and their community assemblages are sometimes structured, while they appeared to be randomly assembled at other times. Whenever non-randomness of diatoms and macroinvertebrates co-occurrences was detected, it suggested aggregation. Moreover, the possible predatory relationship between different macroinvertebrates taxa should be investigated, as it could reveal important scenarios in the establishment of macroinvertebrate structured communities on plastic litter, including taxa that exploit different ecological niches. This could lead to an enrichment of the biological community within areas impacted by plastics
Is the weight of plastic litter correlated with vegetal wrack? A case study from a Central Italian beach
No full textEpiplastic microhabitats for epibenthic organisms: a new inland water frontier for diatoms
No full textPlastic pollution is widespread in each type of ecosystems. However, the colonization events of microorganisms on plastics seem to be neglected in inland waters. Therefore, in this study we analyze the possible colonization on the surface (hereafter epiplastic microhabitats) of two typology of plastic supports by diatom community. Specifically, we located 20 supports in expanded polystyrene and 20 in polyethylene terephthalate both floating and dipped (~ 1 m) in a central Italian shallow water pond, in order to evaluate the diachronic colonization of diatoms from November 2019 to August 2020. Our result showed the tendency in colonizing both epiplastic microhabitats without significant differences in number of species; additionally, depth does not appear to affect the number of species. As regard the temporal colonization, the number of species tends to increase over time from autumn-winter to spring-summer in both types of epiplastic microhabitats and depth. Instead, increase in dominance of some species over time has been demonstrated: only a few species keep a high number of individuals compared to the others; therefore, the number of individuals within the species is not uniformly distributed. These results suggest the tendency of diatom community to colonize plastic supports in lentic waters, and this evidence can be very important because artificial supports can increase the surface available for the settlement of the algae community with an increase of productivity and the colonization of new communities of different taxa. Further studies are mandatory to investigate the possible effects on the epiplastic community and the ecological implications in freshwater environments. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11356-022-23335-8
Passive biomonitoring of airborne microplastics using lichens: A comparison between urban, natural and protected environments
No full textCurrently, natural and urban ecosystems are affected by different types of atmospheric deposition, which can compromise the balance of the environment. Plastic pollution represents one of the major threats for biota, including lichens. Epiphytic lichens have value as bioindicators of environmental pollution, climate change, and anthropic impacts. In this study, we aim to investigate the lichen bioaccumulation of airborne microplastics along an anthropogenic pollution gradient. We sampled lichens from the Genera Cladonia and Xanthoria to highlight the effectiveness of lichens as tools for passive biomonitoring of microplastics. We chose three sites, a “natural site” in Altipiani di Arcinazzo, a “protected site” in Castelporziano Presidential estate and an “urban site” in the centre of Rome. Overall, we sampled 90 lichens, observed for external plastic entrapment, melt in oxygen peroxide and analysed for plastic entrapment. To validate the method, we calculated recovery rates of microplastics in lichen. Particularly, 253 MPs particles were detected across the 90 lichen samples: 97 % were fibers, and 3 % were fragments. A gradient in the number of microplastic fibers across the sites emerged, with increasing accumulation of microplastics from the natural site (n = 58) to the urban site (n = 116), with a direct relationship between the length and abundance of airborne microplastic fibers. Moreover, we detected the first evidences of airborne mesoplastics entrapped by lichens. On average, the natural site experienced the shortest fibre length and the centre of Rome the longest. No differences in microplastics accumulation emerged from the two genera. Our results indicated that lichens can effectively be used for passive biomonitoring of microplastic deposition. In this scenario, the role of lichens in entrapping microplastics and protecting pristine areas must be investigated. Furthermore, considering the impact that airborne microplastics can have on human health and the effectiveness of lichens as airborne microplastic bioindicators, their use is encourage
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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