What role do environmental and anthropogenic factors play in the variability of benthic macrofauna in the northern lagoon of Tunis?

The northern lagoon of Tunis is closed, except for a limited communication with the sea via a very narrow channel. It is subjected, as the majority of Mediterranean lagoons, to environmental/anthropogenic constraints related mainly to the slowness of circulation and renewal of its waters, and also to surrounding human activities. Fifteen stations distributed in the northern lagoon of Tunis were sampled seasonally. The main physicochemical parameters of the water and the sediment were measured and the macro-invertebrates were sampled and identified. Results show that the nitrogen and phosphorus nutrients are relatively low in the study site compared with other Tunisian and Mediterranean lagoons, and the dissolved oxygen content and the pH are relatively satisfactory. However, the temperature and salinity which are higher compared with other Tunisian lagoons show remarkable seasonal variations, and seem to play interesting role in shaping community structure. Thus, the macrofauna community is poorly diversified and impoverished during warm/dry seasons, but slightly improved with precipitation and flow of freshwater during cool/rainy seasons. According to our own results and those of the literature, it seems that the northern lagoon of Tunis has for several years been affected by some major factors, mainly high temperature and salinity, sediment silting and perhaps an excess of organic matter. This has led to deep changes in the macrofauna community before being in its current status