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CONSERVATION STATUS AND TRAJECTORIES OF CHANGE IN MARINE COASTAL ECOSYSTEMS
No full textMarine environments play a central role for the planet, yet an understanding of how climate change is affecting marine ecosystems has been poorly developed. There is now growing evidence that human activities are driving rapid changes from local to global scale. In last decades, the rates of change is accelerating and may exceed the potential tolerance of many organisms to adapt. Ecological systems and marine organisms have evolved under different regimes of stress and disturbances both of natural and anthropic origin and intrinsically connected. No ecosystem is unaffected and marine coastal habitats are particularly sensitive due to the convergence of multiple stressors.
The present work attempts to investigate how variable patterns of stress and disturbance influence the change in marine ecosystems, looking at two iconic coastal habitats: seagrass beds and coral reefs. Effects due to the anthropogenic pressure and a severe storm are here investigated as stress and disturbance respectively, on the endemic Mediterranean seagrass Posidonia oceanica. Thermal anomalies causing repeated coral bleaching events are considered as disturbances on Maldivian coral reefs, while the reduced pH environment that is created at shallow hydrothermal vents of North Sulawesi (Indonesia) is seen as a stress simulating climate and human impact on benthic habitats. The study of change in coastal ecosystems has been carried out by means of several approaches including the comparison with long-time series, the use of indicators able to return a value of ecological status, retrospective analyses and modelling.
The present work confirms the complexity of the interactions between stresses and disturbances, different in scale and intensity, operating on a same ecosystem.
The increase in seawater temperature starting from the 1980-90s can be identified as a common driver of change in both seagrass meadows and coral reefs ecosystems.
In P. oceanica meadows of the Ligurian Sea, anthropic pressures remain the primary causes of impact, although, high intensity, pulse disturbances demonstrated that a single event is able to cause the same loss resulting from hundreds of years of chronic stress.
Benthic habitats in close proximity to hydrothermal vents at tropical latitudes seem not negatively affected by the reduced pH as a chronic stress, while, in Maldivian coral reefs, the ability to cope with thermal disturbances seems to be dependent on coral genera.
Benthic ecosystems could develop a certain adjustment capacity to chronic stress to the detriment of an enhanced sensitivity towards disturbances but this is of concerns regarding the predicted increase of high intensity disturbances due to climate change.
Moreover, chronic stress and disturbances invariably co-occur, so it becomes difficult to assess which may be the proximate cause of ecosystem change.
Data on benthic communities suggest that marine habitats are experiencing phase-shifts toward alternative and unknown states. Consequently, future marine habitats will likely lose their original features acquiring a new different shape.
Continuing studies and long-term series of data will remain the most effective tool to validate these predictions and evaluate temporal patterns
Coral reefs in a changing climate regime: revisitation of lagoon and ocean sites in a remote Maldivian atoll
No full textHydrothermal waters enriched in silica promote the development of a sponge community in North Sulawesi (Indonesia)
No full textTwo shallow hydrothermal vents were investigated by SCUBA diving to evaluate their influence on the structure and diversity of a sponge community living close to the vent outflow, in the equatorial Pacific Ocean just off the coast of North Sulawesi, Indonesia (1°40.361ʹN, 125°8.112ʹE). No sponges identified were vent-obligate species, since they are found in the surrounding coral reefs too. The sponges were strongly attracted by the vent, concentrating in an area of a few meters around it, where they reached covering values up to 70% in the deeper vent and up to 42% in the shallower one. The high silica concentration, 8.5 mg L−1Si (deep vent) and 5 mg L−1Si (shallow vent), in hot spring water (90°C) was the putative environmental factor driving the sponge settlement and growth. These organisms take advantage of the increased silica availability that, facilitating skeleton formation, probably promotes sponge growth. This hypothesis is in agreement with the evidence that the spicules of the sponge specimens living around the hot springs have a thickness about double that of conspecific specimens present on the coral reefs at least 300 m away
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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