Overview on the state of marine remarkable habitats and their biodiversity in front of tourism activities and other disturbances in Tunisia

Abstract

In general, biodiversity in the Mediterranean Sea is concentrated in the 0-50 m deep coastal strip. It is linked mainly to photic, climatic and hydrodynamic factors. Similarly, some ecosystems are characterized by high biodiversity/biological productivity and high presence of endemic, rare and threatened species.

In Tunisia, they are particularly lagunar/island ecosystems, submarine banks, Posidonia meadows, coralligenous biocenosis and Cystoseira beds. Among the human activities that threaten marine habitats in Tunisia, we can cite tourism. It is relatively old activity concentrated primarily on the coast, notably on the East coast, Djerba (SE) and Tabarka (NW). It contributes significantly to the national economy, but fluctuating from year to year, mainly since the revolution (2011).

According to international organizations, around 35% of marine species are threatened in the coast of Tunisia. In the Gulf of Gabès, the Posidonia meadows have strongly declined due to several factors, including siltation caused in particular by discharges of phosphogypsum, trawling, organic pollution, and maritime constructions.

Biological invasions also represent an additional disturbance factor which has been accentuated in recent decades with the increase in human activities. Some of them, as blue crabs Portunus segnis (Forskål, 1775) and Callinectes sapidus (Rathbun, 1896), fish species of the genre Lagocephalus introduced in Tunisian waters in recent years and the green algae Caulerpa taxifolia (M. Vahl) C. Agardh, 1817 introduced about thirty years ago, are invasive and considered as the second cause of biodiversity loss.