Première évaluation des potentialités du satellite Spot pour la cartographie des peuplements benthiques superficiels de Méditerranée occidentale

A Spot satellite image was processed to assess the suitability of this facility for the cartography of epibenthic populations and bottom types in the Mediterranean sublittoral fringe. The area studied was on the north coast of Porquerolles island (Hyeres, SE France). The treated data were compared with mapping carried out by diving. We show that satellite remote sensing may permit a distinction between certain epibenthic populations and bottom types down to 10 m depth. Thus the usefulness of the satellite is reduced where the sublittoral is steeply shelving, as the mappable area is narrow and represented by only a few pixels, each of which tends to overlap several separate biocoenoses. The image treated was obtained in June under very favourable conditions, with dense meadows of relatively epiphyte-free Posidonia oceanica seagrass, calm sea, and very clear water. However, much of the image was subject to marked reflectance, which reduced image usefulness. To avoid this problem, future requests for images should take into account the season and parameters, such as overflight time and satellite angle, likely to be associated with high reflectance at the site in question.