Upper slope geomorphology of Sardinian southern continental margin, applications to habitat mapping supporting marine strategy

This work, framed within the Marine Strategy Framework Directive, is focused on Sardinian southern continental margins marine habitat mapping. Aim of this thesis is to produce predictive marine habitat mapping, starting from a detailed geomorphologic study integrated with biological and oceanographic data coming both from original direct surveys than from bibliographic data. Underwater remotely operated vehicles (ROV), coupled with multibeam echo-sounder (MBES), enabled to perform interpretative hypothesis validation, controlled sampling and detailed observation of specific mesophotic habitats with noninvasive protocols, which are particularly relevant for habitats of conservation interest. Marine habitat mapping represents the best estimation of the distribution of habitats in a place and at a particular time, this goal have been focused on target biocoenosis A4.26 – “Mediterranean coralligenous communities moderately exposed to hydrodynamic action” and A4.713 – “Caves and overhangs with Corallium rubrum”, as defined by EUNIS classification (European Nature Information System), subsequently reunite under the name of Coralligenous Biocoenosis for the mapping of which has been reached a high level of confidence. Principal drivers for seabed habitat distributions include the type of seabed substrate, depth, light availability and the energy of water movements. For the very first time on Sardinian southern margin a multidisciplinary approach has been used to study the relationship between biotic and abiotic components of marine habitats and how seabed morphologic features influences different benthic biocoenosis development styles, geomorphologic characteristics of settlement for substrates could be important factors structuring benthic biodiversity, by affecting sediment accumulation rates, bottom currents and, ultimately, the rates of food supply. These biocoenosis hosts relevant commercially relevant species, as the blue and the giant red shrimp which represent the most important demersal resources for trawling fleet of Sardinia

LANDSLIDES AND POCKFORMS OF SOUTHERN SARDINIAN MARGIN

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CONTINENTAL SHELF AND SLOPE GEOMORPHOLOGY: MARINE SLUMPING INDUCED BY HYPERPYCNAL FLOWS (SARDINIAN SOUTHERN CONTINENTAL MARGIN)

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HABITAT MAPPING AND PALAEO-SEALEVELS OF THE LAST GLACIAL MAXIMUM COASTLINE ON THE SAN PIETRO CONTINENTAL SHELF (SW SARDINIA)

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Shorelines changes and human settlements dynamics in the Lagoon of Mistras- river Tirso coastal plane in the last 3 ky (Middle Bronze-High Middle Ages)

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Morfologia e dinamica delle frane sottomarine potenzialmente tzunamogeniche del margine meridionale sardo (Progetto MAGIC)

Tsunamis are tipically related to several triggering events including earthquakes generated along subduction zones extending up to several hundreds kilometers in lenght, the gravitational massive collapse of volcanic buildings, cliffs or submarine landslides (TINTI ET ALII, 1999; FRYER ET ALII, 2004; MCADOO &WATTS, 2004). Until recent years, tsunamis associated with gravitational events, have been considered very rare, restricted to limited areas and with less energy than the earthquakes generated tsunamis. Recent studies show that the landslides produced tsunamis can be frequent as much as those induced by earthquakes and are also able to generate extreme waves that may affect coastal areas (MCMURTHY ET ALII, 2004; LEE ET ALII, 2007). Considering the actual population growth and industrialization of coastal areas, these are important data implying that tsunami hazard should be studied not only in tectonically active areas, but also in passive margin contexts where gravitational processes can frequently occur (GARZIGLIA ET ALII, 2007). Within the MAGIC project (Marine Geohazard Along the Italian Coast) during the “Sardegna 2009” and “Sardegna 2010” cruises, carried out with the R/V “Universitatis”, multibeam surveys with RESON 8160, high resolution seismic surveys by CHIRP Subbottom ( 500Hz/13,5kHz) and sparker surveys APPLIED ACOUSTICCSP2200 (10/2000 J) were carried out in the southern and western Sardinian margin at depths between -50 and -2200 m. In this work several complex landslides, detected in the upper Sulcis slope and in the Cagliari gulf were analyzed

Monitoraggio e gestione dei litorali

Abstrac

Multidisciplinary and multiscalar approach for a sustainable management of Red Coral (Corallium rubrum,L.1758) from the island of Sardinia (West Mediterranean Sea)

Red Coral, Corallium rubrum (L.1758), is an important socio-economic resource for the Mediterranean community and the island of Sardinia, due to its great commercial value. Since 1979, regional law regulates colonies harvesting for its correct management and conservation. Nevertheless, all available data that provided the scientific base for the actual law, came from landing data obtained from fishermen, leaving huge lacks of knowledge in terms of investigated areas (and relative geological features) and representativeness of the state of the stock. In this work we report an example of multidisciplinary and approach, both biological and geological, for an unprecedented multiscalar mapping of red coral colonies that can provide important improvement in its conservation. A Geological survey (“MaGIC” project, Marine Geohazard along Italian Coasts) using Multibeam, Side Scan Sonar and Sparker 500J was conducted in Summer 2009, providing a detailed data coverage of two key areas of South Sardinia continental shelf San Pietro Island and Cape Carbonara. Data collected during the survey were integrated with CARG project (Official National Italian Geological Cartography). This Geomorphological analysis provided a usefull guideline to define and map harvesting areas and planning the further ROV survey. The Biological R.O.V survey was carried out in Summer 2011; more than 2000 photos were Geo-referenced to the multibeam map of the bottom, and examined using CPCe (Coral Point Count with Excel extensions) Software in order to create a database on the abundance and morphometry of colonies. Colonies were divided in 3 categories: Ramified, non ramified and dead colonies. For the morphometric database, the basal diameter and maximum height of the colony was measured along with number and type of ramifications. The population structure was also calculated for better describe the status of the stock. This mapping approach has allowed scientist to discover new banks of coral that can could be harvested in a short/long- time period in less known areas as well as a better overview of sites already used for harvesting. Morphological adaptations of Red coral colonies to environmental features can be evaluated thanks to to the multibeam references. In conclusion these data can provide the new scientific base for a local-based specific regulation for C.rubrum harvesting

Geomorphology of the continental shelf of Tavolara Island (Marine Protected Area ‘Tavolara-Punta Coda Cavallo’ – Sardinia NE)

In this document a geological – geomorphological map in scale 1: 25,000 is presented. The study area is located inside the Protected Marine Area Tavolara – Punta Coda Cavallo, in north-eastern Sardinia. The study was done through integrated analysis of multibeam bathymetric and very high-resolution side scan sonar data, acquired in an area of 163 km2 with the purpose of mapping the main biocoenoses and with particular reference to the coralligenous bioconstructions and the distribution of Posidonia oceanica. The interpretative hypotheses, based on the analysis of geophysical data, have been validated through diving surveys. This map represents a fundamental knowledge base and it constitutes an important technical-scientific support for long-term planning and management of the studied seabed

Deepwater corals biodiversity along roche du large ecosystems with different habitat complexity along the south Sardinia continental margin (CW Mediterranean Sea)

Rocky pinnacles arising from soft bottoms of the circa-littoral zone may host oases of deepwater coral biodiversity: Engineer species that enhance ecosystem’s three-dimensional complexity often acting as shelter for associated fauna that can comprise commercially relevant species. Although variations in beta diversity of these coral oases were recently documented at different spatial scales, information on the role of geomorphogical features of rocky outcrops can be considered mostly an unaddressed issue. To comply with this task, five rocky pinnacles showing different geomorphological features (average slope, ruggedness, sediment accumulation), dwelling between 120 and 170 m depth along south Sardinia continental margin, were investigated by means of ROV imaging. We tested the null hypothesis that coral abundance and diversity [estimated using four black corals (Antipatharia) and seven gorgonians (Alcyonacea) as target species] did not differ among investigated sites. Overall, total coral abundance varied from 1.35 to 7.23 col m2; Callogorgia verticillata, followed by Eunicella cavolinii and Corallium rubrum were the most abundant gorgonians, while Antipathella subpinnata and Parantipathes larix were the most abundant black corals. Through uni- and multivariate analyses, significant differences in corals biodiversity were identified, allowing us to reject the null hypothesis, emphasizing a remarkable variability in beta diversity, apparently following variations in geo-morphological features of investigated pinnacles. Moreover, a visual census of anthropogenic debris revealed that lost fishing gears represented the most frequently observed debris, stressing the need to identify further and more focused strategies of conservation to protect these oases of coral biodiversity