Mapping Posidonia oceanica meadows through time. A story of precision, evaluation and fragmentation

摘要: Over the last decades, the interest in mapping Posidonia oceanica beds has increased along with the improvement of the equipment’s precision of data acquisition. In Calvi Bay (Corsica, France) the meadows cover an area of about 5 km² and are found at a depth ranging from 3 m to 37 m. The availability of three distinct datasets for 1997, 2002 and 2010 allowed to assess changes in the patchiness of the meadows in the bay and to investigate evolution of maps precision through a surface analysis via GIS software. Thus, three maps were elaborated combining aerial photographs and side scan sonar images. The meadows percentage of cover through time was assessed using four bathymetric sections: 0-10 m, 11-20 m, 21-30 m and 31-40 m.Differences in the patchiness of P. oceanica meadows between 1997 and 2010 appear to be moderate (less than 3%) in the sections 0-10 m and 11-20 m and then greatly …