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A project to reconstruct 9~km of sandy beaches located in the north-eastern part of Jerba Island (Tunisia) is presented. The beaches face the Mediterranean Sea, and multiple offshore sand bars are a common feature in this area. The visible and underwater parts of the beaches have been eroded by sand losses, shoreline retreats, recurrent flooding, steepened nearshore profiles and continuosly decreased volume of offshore sand bars. Erosion and degradation of the coastal dunes have resulted from recreational developments in the area. Earlier `hard' protection measures implemented, such as seawalls, ripraps, etc., failed. Our project proposes a `soft' protection method that involves supplying the lacking sediment to 'strategic' places in the nearshore zones for the restoration of their wave-dominated dynamic equilibrium. Our recommendations for the project are based on historical data, observations, field measurements and numerical simulations, using a mathematical model of wave-seabed interactions (Boczar-Karakiewicz et al. 1987), with initial data provided by field measurements of waves, currents and morphology. The model predicts the formation of longshore bars and their site-specific dynamics in response to sequences of storm events in the local wave climate, while reproducing the observed quasi-periodicity of beach erosion and recovery. The conclusions of the project recommend the nourishment of two offshore bars and reconstruction of the beaches to a width of some 70 m (their pre-erosion state). The increased volume of the nourished bars will assure protection and stable conditions for the reconstructed beaches and prevent flooding. Boczar-Karakiewicz B., Bona J.L. and Cohen D.L., 1987. Interaction of shallow-water waves and bottom topography. In: Dynamical problems in continuum physics, mathematics and its application, J.L. Bona, C. Dafermos, J. Erickson & D. Kinderlehrer, editors, Springer-Verlag, New York, IMA Series in Mathematics and its Applications, 4, 131-176.
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We studied the spring spatial distribution of the ciliate community coupled with environmental factors along the coast and in the open sea at 30 stations sampled (between 27 May and 9 June 2006) in the Gulf of Gabes (Tunisia, Eastern Mediterranean Sea). A total of 61 taxa belonging to 36 genera and 5 taxonomic classes were identified. The ciliate assemblage was numerically dominated by spirotrichs (86% of total ciliates). This group is largely dominated by the choreotrichs (92%) among which tintinnids represented 99%. The total ciliates abundance showed a gradual decrease from the coastal area to the open sea and an increase from the surface to the bottom. The maximum abundance (400 cells l-1) and biomass (6.29 µgC l-1) were found in station 27, close to Djerba Island. The tinitinnid Rhabdonella spiralis was cosmopolitan, being found almost at every station and at each depth, while other taxa may be exclusive to the neritic area, others to the open sea area. The distribution of species in the Gulf of Gabes seemed most likely influenced by the combined effects of hydrographic conditions, zooplankton predation and urban interferences.
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