This is the typical Mediterranean ecosystem. It represents a large pole biodiversity. The magnoliophyte Posidonia oceanica is endemic.
It lives in a coastal strip from the shore to the lower limit of the infra coastline. It has been shown that 20 to 25% of Mediterranean species live in the Posidonia meadows. In the bibliography, it cites more than 400 plant species and 1,000 animal species living within these beds on secured rhizomes, leaves of Posidonia oceanica. The state of the ecosystem in Tunisia and especially in the South East of Tunisia is fragile to various causes:
- Direct causes (mechanical tearing rhizomes of Posidonia, destabilizing nature of the substrate, decreased water transparency, etc.);
- Indirect causes that usually succeed the Posidonia meadows of seagrass and Caulerpa contributing to the provision of organic matter (humus) required, among others, the development of seagrass Posidonia.
These meadows, themselves, have been greatly reduced because of trawling. These meadows are important off the Tunisian coast, and 167 km² were listed in the Gulf of Hammamet in 1993. In the Gulf of Gabes, it is estimated that only 5% are still "available" in the Gulf of Gabes, although some areas are equipped with very large areas such as reef Kerkennah, the northern area between Cape Farina, Cani islands and Bizerte, or the areas extending from eastern Djerba to the tunio-Libyan border and in particular shallows. Or the areas Extending the gold from Djerba to the eastern Libyan border and tunio-In Particular shallows