Etat de la bionomie benthique des étages infra et circalittoral du Golfe de Gabes

Abstract

Several marine surveys conducted since 1988, including in particular 3 marine prospecting campaigns in 1990, 1991 and 1992, allow the visit by scuba diving of 143 stations in the Gulf of Gabes. As a result, we draw up both a review of the bottom substratum and the state of the Posidonia oceanica meadows. The analysis of their distribution, according to the depth and the type of substratum, as well as the comparison of few characteristics of their phenology with other Mediterranean stations, constitutes the main axis of this study. The whole prospecting reveal an impressive degradation and regression of the meadows area coverage, except few rare littoral stations (mainly on the western coasts of Djerba). We were also concerned by the absence of Cymodocea nodosa, Zostera nolti, and Caulerpa prolifera. Besides, we also draw up the inventory of the most remarkable macrobenthic species of the Gulf of Gabes and identified the main type substratum and bottoms. Qualitative transformations which occur in this area were also analysed. These major changes are the results of the global silting up of the substratum of the gulf which, with other factors such as the abiotic ones, further an abnormal transgression of the upper limit of the circalittoral level.