**2. Biodiversity of halophilic microalgae in solar saltern of Sfax**

The Sfax solar salternor the Thyna salt works (**Figure 1**) is an artificial system located in the Gulf of Gabes in an arid climate (34° 39′N and 10° 42′E). This system is composed of several interconnected shallow ponds (20 to 70 cm deep) with increasing salinities from the water intake (40 PSU) to the salt Tables (450 PSU) [9]. The saline is separated from the sea by a dam of red silt about 4 m high running along the southern coast of the city of Sfax for about 13 km (**Figure 1**), from the port area to the village of Gargour, occupying an area of 1500 ha [29]. It is one of the most

*The Solar Saltern of Sfax: Diversity of Hyperhalophilic Microalgae Species as a Promising... DOI: http://dx.doi.org/10.5772/intechopen.104712*

**Figure 1.** *General map of the Sfax Saltern showing the three levels of increasing salinity.*



#### **Table 1.**

*Classification of microalgae species recorded in Sfax solar saltern according to the salinity gradient [9].*

#### **Figure 2.**

*Mean relative contribution of microalgae groups to total microalgae biomass in six ponds of increasing salinity in the saline of Sfax Tunisia [30].*

important salt production areas in Tunisia (300,000 T of salt per year). A total of 45 microalgae taxa were recorded from the Sfax solar saltern and identified belonging to five groups: diatoms, dinoflagellates, Chlorophyceae, Euglenophyceae and

*The Solar Saltern of Sfax: Diversity of Hyperhalophilic Microalgae Species as a Promising... DOI: http://dx.doi.org/10.5772/intechopen.104712*

Cyanobacteria. For each group, we clearly observed a marked decrease in the number of taxa with the increase of salinity (**Table 1**, **Figure 2**). Diatoms were dominant in ponds that have salinity ranges from 40 to 80 PSU (67.95% of the microalgae total abundance), whereas the dinoflagellates represented only 22.19% and Euglenophyceae were poorly represented in this pond (1.2%) (**Figure 2**). Dinoflagellates dominated the densities and biomasses of microalgae in the ponds of 80–200 PSU, contributing to 56.7% and 34.4% of the microalgae total abundance, respectively. Chlorophytes largely dominated in the crystallization ponds>200 salinity which accounting for 69.1% of the total microalgae. While Cyanobacteria were relatively abundant in ponds of medium salinity (19.9%) they were rare in hypersaline ponds (0.5%) (**Figure 2**, **Table 1**).
