Seasonal and Spatial Variability of the Community and Trophic Structure of the Benthic Macrofauna within Tunisian Lagoonal and Marine Coastal Areas (Southwestern Mediterranean)

Three Tunisian lagoon and coast locations, diversely subjected to human activities and differing according to their degree of communication with the sea, were studied seasonally. Main environmental parameters and the trophic structure and biodiversity parameters of the benthic macrofauna were determined and analysed. Results show that the sites are quite different and each one has its own seasonal fluctuation linked certainly to environmental and anthropogenic factors. In the almost-enclosed lagoon of Ghar El-Melh with high salinity, selective deposit feeders dominate in spring and summer, and in the other seasons the trophic structure is rather balanced. In the southern lagoon of Tunis where environmental factors are more fluctuating and man-made activities of Tunis City and its suburbs are more important, the community is clearly more enriched because of the strong dominance of leader species. In this site, micrograzers dominate clearly all year, with a slight increase in winter. However, in the Bay of Tunis, which is a coastal area more open to the sea, the community is clearly less enriched and no dominance of the leader species was noted. In this site, the trophic structure seems to be clearly more balanced since most trophic groups are almost equally represented.