Analisi spaziale e temporale dello stato di salute delle praterie di Posidonia oceanica presenti lungo il litorale di Civitavecchia (Lazio, Italia)
Author(s)
Gnisci, Valentina
Date Issued
June 10, 2014
Type
Doctoral Thesis
Abstract
Posidonia oceanica is an endemic seagrass of Mediterranean Sea and it forms wide meadows
along all the coast of the basin, from surface to 40 m depth; the importance of Posidonia oceanica
meadows in keeping coastal ecological equilibrium is well known all over the world. The principal
causes of meadows regression are the reduction of water column transparency and the variation in
sediment balance along shore. These are due to the change of land use, the typology of sediments
transported by rivers and to the modification of coastline.
The study area is located on northern Latium, in particular Civitavecchia coast; this area is
characterized by the presence of a complex geomorphology, consequently P. oceanica meadows
have settled on both sandy and rocky bottoms, showing a highly fragmented landscape.
Furthermore, there are several human activities that influence the health status of coastal marine
ecosystems; as example, numerous dredging were performed in the port of Civitavecchia, which
may have modified water column transparency.
The aim of this work is to study spatial and temporal variability of Posidonia oceanica
meadows along Civitavecchia coast in relation to the variation of environmental factors, in
particular water column transparency.
Evaluation of health status of Posidonia oceanica meadows was carried out through field
activities, i.e. scientific diving, and laboratory analysis during June 2013; previous studies have
allowed to investigate the evolution of health status of meadows from 2002 to 2013. Environmental
data have been collected during the same period. Informations of water column transparency has
been achieved through remote sensing data, as a light coefficient attenuation at 490 nm (Kd 490); to
estimate the quantities and qualities of sediment transported by rivers, land use and rainfall data has
been collected from Corine programme and regional hydrographic services. Furthermore, the use of
mathematical models has made possible the simulation of the dispersion of suspended particles
coming from river mouths and dredging activities; this has allowed to evaluate the influence of
natural and anthropic disturbances on Posidonia oceanica meadows.
Spatial analysis of health status of meadows has shown the presence of a complex and
fragmented landscape; spatial distribution of Posidonia mainly depends on edaphic factors and
presence of river mouths; temporal analysis has not highlighted significant differences in the health
status of meadows. The analysis of environmental data and results of mathematical model have
shown as dredging activities have not influenced the evolution of Posidonia oceanica meadows
present in the area.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
Subjects
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