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Item Type: Tesi di dottorato
Uncontrolled Keywords: Polychaete assemblages, biocoenosis, soft-seabed
Date Deposited: 14 Dec 2011 11:59
Last Modified: 30 Apr 2014 19:48


Since research on soft-seabed macrozoobenthic community, including polychaetes, of Mediterranean and in particular Italian Saes still display a lack of data concerning taxonomic aspects and species distribution patterns, and the pre-existing information are frequently outdated, further studies and revisions of data are a primary necessity. These habitats are widely common in coastal areas all over the world and host most of sensitive and protected benthic habitats, species and typical biocoenoses as well as most of the human activities. At the same time, in a framework of an ecological sustainability of human activities, such as sand dredging extraction, upon the marine environment, it is important to understand the extent of their effects on marine ecosystem, to protect the environment itself and to develop management strategies. In Italy, the use of marine relict sands, to repair the effects of the increasing coastal erosion, has become more common in the last decades. The efficiency of biodiversity and environmental monitoring studies in marine environments is strongly influenced by the selection of the spatial and temporal scale. Investigations at regional as well as at adequate temporal scale allow to analyse the comprehensive variability of biological systems, strongly influenced by the interactions of numerous environmental factors (depth, geographic position and sediment types). To display the variability of polychaetes diversity patterns in space and time, and to investigate how this variability is related to the habitat characteristics and human impacts, this research, is aimed to:1) identify diversity distribution patterns of polychaete assemblages and species at a regional (Latium Continental Shelf) related to depth, sediment grain size, latitude and longitude; 2) compare information, concerning the spatial distribution and ecology (related to sediment composition and depth range) of a number of selected soft-sediment polychaetes species, obtained at regional (Latium Continental Shelf) and national scale (Italian Continental Shelf); 3) assess the effects of human activities (sand dredging) on marine ecosystems at a local scale through the analysis of biological diversity variation over time. The amount of pre-existing studies, carried out in Mediterranean and in particular along the Italian Seas, concerning macrozoobenthos species, polychaetes, and their spatial distribution as well as the role of macrozoobenthic community for the environmental assessment, contributes to be the background of this research focused on the assessment of ISPRA multidisciplinary data-set, from environmental monitoring programmes, as a source of valuable scientific data. Results from PERMANOVA, CCA, BIOENV and Spearman rank correlation analyses, have pointed out that the three main categories explaining the drivers of biodiversity patterns in the Tyrrhenian continental shelf are: bathymetric gradients, geographical features, responsible for the north-south gradient in environmental conditions, and environmental heterogeneity (i.e. grain size distribution, habitat complexity). ISA analysis showed that some species distribution is significantly associated to definite sediment grain sizes and depth ranges confirming or updating the ecological characteristics of the investigated species as emerged from the comparison of results of this study with pre-existing knowledge. Moreover, the species distribution patterns as well as the assemblages composition observed along the Latium continental shelf (tested with PERMDISP analysis), confirm results obtained in previous studies carried out in neighbouring areas along Tyrrhenian Sea. A continuum of species distribution along Tyrrhenian continental shelf can be expected and represented by means species diversity maps (by Universal Kriging interpolator) able to represent comprehensive species diversity distribution patterns at the regional scale; despite polychaetes have been demonstrated to be able to respond quickly to changes in their environment as a consequence of dredging activities, the assessment of the effects of these activities upon benthic organisms is quite complex to define.

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