1,721,066 research outputs found
Abundance and orientation responses of the sandhopper Talitrus saltator to beach nourishment and groynes building at San Rossore natural park, Tuscany, Italy
No full textBeach nourishment and groynes building were implemented to counteract erosion in sandy beaches located at San Rossore natural park (Tuscany, Italy), near the mouth of Arno river. From 2000 to 2003, nine groynes were built along 3.6 km of coastline at intervals of ca. 400 m, and two of the eight beach segments were filled with marble gravel. Here, we analysed the effects of these beach changes on the abundance and behaviour of the amphipod Talitrus saltator, using field and laboratory observations. Sampling with pitfall traps in order to use the capture frequency as a proxy of abundance was performed bimonthly from September 2004 to January 2006, and orientation experiments were carried out in autumn (2004 and 2005), and spring and summer 2005. Physical variables (beach width, swash width, beach slope, sand penetrability, mean grain size and salinity) were also recorded. The abundance of T. saltator increased with the distance from the river mouth, towards sites with: negligible amounts of marble locally used for nourishment; higher beach width and salinity; lower slope and penetrability values; medium grain sizes, and during the spring/summer seasons. A Generalized Linear Model with a predictive power of 64.5% considered three main descriptors in the model as significant: distance from the river mouth, sand penetrability and a seasonal factor. Orientation experiments showed a highly variable behaviour among sites, depending on coastal stability: at the site stabilized by the concurrent actions of nourishment and groynes protection measures, sandhoppers were oriented to the shoreline direction by using a sun compass; alternatively, at a site situated only 2 km from the nourished sites, they showed scattered orientation. These between-site differences in orientation, described through Spherically Projected Linear Models, were consistent throughout the study period. Different responses obtained at the individual (orientation) and population (captures) levels stress the need to account for several bioindicators to characterize biotic responses to both natural and anthropogenic changes in sandy beaches. © 2007 Springer-Verlag
Effects of beach nourishment and groynes building on population and community descriptors of mobile arthropodofauna
No full textFor decades beach nourishment and groyne building have been used to combat sandy beach erosion, but their effects on sandy beach macrofauna are often neglected. Here, we analysed the effects of beach nourishment and groyne building on a sandy beach within the San Rossore-Migliarino-Massaciuccoli Regional Park (a natural park in Tuscany, Italy) on two different levels of organization: the abundance of the crustacean amphipod Talitrus saltator (population level) and community descriptors of the sandy beach arthropod fauna (community level), with emphasis on supralittoral species. Samples were taken bimonthly from September 2004 to January 2006 using pitfall traps. T. saltator abundance was described by generalized linear models (GLMs) and arthropodofauna community descriptors were estimated by species number, diversity indexes and ordered with multivariate ordination methods. The abundance of T. saltator in different seasons was influenced by the month of sampling during the autumn-winter season and by beach width, substrate penetrability and the "species number" biotic factor during the spring-summer season. The abundance models revealed no direct effects of beach nourishment. T. saltator was shown to be both a typifying and discriminating species, confirming its key role in the community of sandy beaches. The arthropodofauna community showed sensitivity to the substrate grain size and quality changes generated by beach nourishment, as the community composition changed at the nourished sites in line with seasonal dynamics. Human actions to stabilise the shoreline therefore emerged as a driving environmental feature, altering the beach's physical characteristics and consequently its fauna on different organizational levels: it was shown to have a direct effect on the arthropodofauna community structure and on sandhopper population abundance by determining habitat availability. © 2008 Elsevier Ltd. All rights reserved
Testing the habitat safety hypothesis with behavioural field experiments: Amphipod orientation on sandy beaches with contrasting morphodynamics
No full textUnderstanding behavioural adaptations in sandy beach macrofauna has been a major step in theoretical development of sandy beach ecology. In particular, behavioural studies in supralittoralamphipods have been useful in understanding macrofaunal responses and adaptations to environmental changes in these dynamic ecosystems. The predictions of the Habitat Safety Hypothesis (HSH) were tested for the first time on Atlantorchestoidea brasiliensis through orientation experiments carried out on 2 sandy beaches, one dissipative and the other reflective. Orientation patterns of A. brasiliensis followed the trend predicted by the HSH: even though sandhoppers oriented seawards on both beaches using a sun compass, the orientation on the reflective beach was more precise than on the dissipative one. Thus, stability conditions in the supralittoral zone of the reflective beach favoured a higher precision of the sun compass. The precision of seawards orientation on the dissipative beach increased when landscape references were added to the sun compass mechanism. The response to an unexpected object was also experimentally tested by use of a visual pattern, and a higher individual variability in the orientation of the reflective beach population was found. Thus, orientation strategies in sandy beach environments seem to respond to the stability of the supralittoral zone, widening the general pattern predicted by the HSH for the supralittoral fauna to the behavioural traits of the population. © Inter-Research 2009 www.int-res.com
Macroinvertebrates as indicators of human disturbances on sandy beaches: A global review
No full textSandy beaches are ecosystems under increasing human pressure that require efficient management and conservation strategies. Resident macroinvertebrates usually respond to disturbances by changing their behaviour and abundance, and therefore they may be used as indicator species using simple and low-cost monitoring strategies. We synthesize information from the scientific literature on the use of sandy beach macroinvertebrates as indicators of human disturbances operating at local scales. Response ratios were applied to perform a meta-analysis supported by empirical data to objectively assess the magnitude of human disturbances on beach fauna. The “compare and contrast” approach represented some 80% of the studies. Gradient assessments were performed by 16% of the studies, though without determining thresholds of disturbance. Long-term monitoring (encompassing more than two years) was the general approach used in studies about harvesting, but it was not used when assessing other type of disturbances. Causality relationships and mechanisms underlying impacts were rarely assessed. Useful indicators to specific human disturbances were: 1) ghost crabs, which indicate the negative effects of vehicle traffic and nourishment; 2) talitrids as indicators of trampling and mechanical cleaning; and 3) clams as indicators of harvesting. As beaches are affected by multiple stressors acting simultaneously, the relative importance of each one has been difficult to reveal. It remains a priority to identify how different human disturbances are affecting macroinvertebrates under a range of diffuse impacts. Such results would allow for the depiction of patterns and future studies should prioritize gradient analyses and manipulative experiments to provide thresholds of specific stressors and mechanisms of impacts
Coupling beach ecology and macroplastics litter studies: Current trends and the way ahead
Full text linkAs sites of floating marine material deposition, sandy beaches accumulate marine litter. While research and
assessment on beach litter is increasing and involves various actors (scientists, society and NGOs), there is the
need to assess current and future dominant trends, directions and priorities in that research. As such, a textural
co-occurrence analysis was applied to published scientific literature. Words were considered both singly and as
part of compound terms related to concepts relevant to sandy beach ecology: morphodynamic state; Littoral
Active Zone; indicator fauna. Litter as a compound term was also included. The main co-occurrences were found
within compounds, with scarce interaction of “morphodynamic state” with the others, indicating the need for
further integration of beach ecology paradigms into beached plastics studies. Three approaches are proposed to
overcome the research limits highlighted: the unequivocation of terms, the consideration of adequate scales, and
the attention to dynamics rather than just patterns
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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