Sedimentary dynamics and ecological state of Nakta tidal flat （littoral）, South of Sfax, Gulf of Gabès, Tunisia）

The tidal flat of Nakta is located in the northern part of the gulf of Gabes and in the southern coast of Sfax. It corresponds to a flat reef protected from less topography, with a slope ranging between 2° and 4°, which borders the Gargour Wadi. The study sector is renowned to have moderate hydrodynamics which lasts almost for two millenary （14C isotopic dating）. The sedimentological study of the Nakta tidal flat revealed different facies： fine-grained sand in the intertidal zone and carbonated muddy sand in the infratidal zone. Equilibrium state of the Nakta ecosystem depends entirely on tide currents, which mainly inhibit drift currents. The Nakta tidal flat is characterized by a variety of faunal species （Cerastoderma glaucum, Arca hoe, Cardita antiquatus, Chlamys varied, Ruditapes deccussatus, Tapes rhomboids, Pinctada radiate, etc.） and floristic diversities （Halocnemum strobilacum, Halimione portulacoides, Enteromorpha linza, Ulva rigida, Cymodocea nodosa, Posidonia oceanica）. The species are abundant in the infratidal zone, while in its intertidal zone, faunal species remain little diversified and are dominated by limivorous diggering. The paleogeographic study of the Nakta tidal flat showed the alternation of regression and transgression periods.