196,159 research outputs found
Policies applying to Posidonia oceanica meadows. in Boudouresque C.F., Bernard G., Bonhomme P., Charbonnel E. Diviacco G. Meinesz A., Pergent-Martini C. Ruitton S, Tunesi L. (eds.) Ramoge and RAC/SPA and GIS publiscer Tunis pagg 48-60 ISBN 2-905540-31-1 http://www.rac-spa.org/sites/default/files/doc_vegetation/ramoge_en.pdf
No full textSpatially Explicit Seagrass Extent Mapping Across the Entire Mediterranean
No full textThe seagrass Posidonia oceanica is the main habitat-forming species of the coastal Mediterranean, providing millennial-scale ecosystem services including habitat provisioning, biodiversity maintenance, food security, coastal protection, and carbon sequestration. Meadows of this endemic seagrass species represent the largest carbon storage among seagrasses around the world, largely contributing to global blue carbon stocks. Yet, the slow growth of this temperate species and the extreme projected temperature and sea-level rise due to climate change increase the risk of reduction and loss of these services. Currently, there are knowledge gaps in its basin-wide spatially explicit extent and relevant accounting, therefore accurate and efficient mapping of its distribution and trajectories of change is needed. Here, we leveraged contemporary advances in Earth Observation-cloud computing, open satellite data, and machine learning-with field observations through a cloud-native geoprocessing framework to account the spatially explicit ecosystem extent of P. oceanica seagrass across its full bioregional scale. Employing 279,186 Sentinel-2 satellite images between 2015 and 2019, and a human-labeled training dataset of 62,928 pixels, we mapped 19,020 km(2) of P. oceanica meadows up to 25 m of depth in 22 Mediterranean countries, across a total seabed area of 56,783 km(2). Using 2,480 independent, field-based points, we observe an overall accuracy of 72%. We include and discuss global and region-specific seagrass blue carbon stocks using our bioregional seagrass extent estimate. As reference data collections, remote sensing technology and biophysical modelling improve and coalesce, such spatial ecosystem extent accounts could further support physical and monetary accounting of seagrass condition and ecosystem services, like blue carbon and coastal biodiversity. We envisage that effective policy uptake of these holistic seagrass accounts in national climate strategies and financing could accelerate transparent natural climate solutions and coastal resilience, far beyond the physical location of seagrass beds
Nouvelles connaissances sur les herbiers tigres de Mediterranee
No full textRésumé
Les herbiers à Posidonia oceanica présentent plusieurs types morpho-structuraux
généralement conditionnés par les conditions de milieu (profondeur, hydrodynamisme,
substrat, pente, turbidité, sédimentation). Du fait de leur rareté, deux structures
particulières, les récifs barrière et les herbiers tigrés, sont considérées depuis une
vingtaine d’années comme des paysages marins menacés. Initialement décrits dans le
golfe de Gabés, à proximité des îles Kerkennah, les herbiers tigrés se présentent sous
forme « de rubans assez étroits qui se développent entre 0.5 et 3 m de profondeur sur
matte ». La mise en place de nouveaux programmes d’études sur les herbiers à
Posidonia oceanica et l’optimisation de l’imagerie satellitaire (accessibilité, résolution,
coût) ont permis d’acquérir de nombreuses données dans plusieurs secteurs de
Méditerranée et d’actualiser notre connaissance de ces structures.
Il apparaît ainsi que les herbiers tigrés sont mieux représentés au niveau de la rive Sud
du bassin (Golfe de Gabès, littoral de Zarzis en Tunisie, lagune de Farwa et littoral à
l’Est de Tripoli en Libye) et dans des îles méditerranéennes (Marsala-Stagnone en
Sicile et Porto-Vecchio en Corse). D’autre part la présence d’herbiers tigrés sur roche
a été observée pour la première fois en Libye sur un platier rocheux à l’Est de Tripoli.
Compte tenu de leur rareté et des pressions qu’elles subissent, il apparaît urgent de
classer ces structures comme « monuments naturels » et mettre en œuvre une politique
efficace pour assurer leur conservatio
SPATIAL AND TEMPORAL VARIATION OF ASSEMBLAGES IN MEDITERRANEAN CORALLIGENOUS REEFS
No full textThe structure, distribution and temporal changes of epibenthic assemblages of Mediterranean coralligenous reef in the Ligurian and Adriatic Sea were investigated by using a multifactorial sampling design. The distribution of taxa were analysed at scales ranging form hundred of meters to tens of kilometres. Temporal variations were analysed among different years. Percentage cover of conspicuous species have been analysed by means of photographic sampling. Strong spatial patterns of taxa distribution were found among coralligenous outcrops in the Adriatic, while in the Ligurian Sea a strong small scale pattern related to habitat orientation was found. There was some temporal fluctuation in abundance of taxa, but no clear patterns were observed. These results suggest that coralligenous assemblages are a patchy habitat where changes in species composition and abundance can occur at a range of spatial scales, down to few meters, moreover, validate the assumption of the limited temporal variability in Mediterranean coralligenous reefs, possibly related to the slow growth rates of the most abundant taxa and the reduced seasonality of physical conditions
The Natural Capital Value of the Seagrass <i>Posidonia oceanica</i> in the North-Western Mediterranean
No full textPosidonia oceanica is an endemic Mediterranean seagrass used as a ‘biological quality element’ in monitoring programmes of the EU Water Framework Directive, providing information about coastal ecosystems status. The regression of P. oceanica meadows caused a growing interest among policy makers to assess the value of seagrasses and to increase their protection. An evaluation of P. oceanica meadows located in the Ligurian-Provençal basin (NW Mediterranean) through a biophysical approach is here developed. Six meadows located in Liguria (Italy) and Corsica (France) were investigated by applying the emergy analysis to assess the natural capital (NC) stocked by leaves and rhizomes components. Results highlighted the importance of carrying out an analysis of the variations in the NC value in both components: rhizomes defined the growth stage and the capacity to store NC over time; leaves provided information on the variability due to disturbances in the water column. Emergy analysis allows defining the NC, in terms of resources needed to maintain the meadows and to provide services to coastal communities. This research is inserted into the effort of incorporating the NC evaluation into marine planning and decision making to achieve nature conservation goals, while ensuring the sustainable exploitation of marine resources
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Assessing Seagrass Restoration Actions through a Micro-Bathymetry Survey Approach (Italy, Mediterranean Sea)
No full textUnderwater photogrammetry provides a means of generating high-resolution products such as dense point clouds, 3D models, and orthomosaics with centimetric scale resolutions. Underwater photogrammetric models can be used to monitor the growth and expansion of benthic communities, including the assessment of the conservation status of seagrass beds and their change over time (time lapse micro-bathymetry) with OBIA classifications (Object-Based Image Analysis). However, one of the most complex aspects of underwater photogrammetry is the accuracy of the 3D models for both the horizontal and vertical components used to estimate the surfaces and volumes of biomass. In this study, a photogrammetry-based micro-bathymetry approach was applied to monitor Posidonia oceanica restoration actions. A procedure for rectifying both the horizontal and vertical elevation data was developed using soundings from high-resolution multibeam bathymetry. Furthermore, a 3D trilateration technique was also tested to collect Ground Control Points (GCPs) together with reference scale bars, both used to estimate the accuracy of the models and orthomosaics. The root mean square error (RMSE) value obtained for the horizontal planimetric measurements was 0.05 m, while the RMSE value for the depth was 0.11 m. Underwater photogrammetry, if properly applied, can provide very high-resolution and accurate models for monitoring seagrass restoration actions for ecological recovery and can be useful for other research purposes in geological and environmental monitoring
Les herbiers de Magnoliophytes marines de Méditerranée: résilience et contribution à l’atténuation des changements climatiques.
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe 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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