Abstract
The Bizerte lagoon belongs to a large lagoonal complex increasingly affected by anthropogenic activities during the last years. At the same time, it is influenced by seawater inputs and by the freshwaters coming from Ichkeul Lake and several wadis, this giving rise to greatly fluctuating environmental conditions. To study the functional organization of the benthic macroinvertebrates, 11 stations facing the main important contamination sources were sampled using a 0.1 m(2) Van Veen grab. Our results showed that the ecosystem presented signs of trophic imbalance and the overall macrobenthic community was very impoverished, despite the apparent satisfactory ecological status showed by biotic indices. In this situation, microbial food web replaced the herbivore one while only some invertebrate species tolerant to environmental fluctuations were able to survive in such conditions.