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

Does increased connectivity with the Mediterranean Sea improve the ecological status of the macroinvertebrates in the lagoon of Boughrara (SW Mediterranean)?

The lagoon of Boughrara is an almost closed system, with limited hydrological connections with the sea. Over the past several decades, the lagoon has been exposed to increased pollution due to growing human activities in the surrounding area. From 2004–2007, the channel “El-Kantra” connecting the lagoon to the sea has been extended with increased mixing with marine waters. In this work, we monitored the ecosystem of the lagoon after its rapid exposure to development and associated pollution. Two marine surveys were carried out in winter 2010 and then in winter 2013; the sediment was sampled and the principal physical and chemical parameters were measured at 13 stations. Results show that aspects of the environmental quality of the lagoon have improved from 2010 to 2013, most likely due to the extension of the channel whereby lagoon waters are better mixed resulting in improved physico-chemical conditions over this timeframe. Nevertheless, the study of the macrobenthic community did not show any improvement. On the contrary, the species richness and the abundance of the macrofauna have decreased, and some tolerant species such as bivalves (Abra alba and Cerastoderma edule) have increased in abundance. This demonstrates continued impacts on the lagoon ecosystem