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.