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The benthic foraminiferal genus Amphistegina is currently expanding its range in the Mediterranean Sea after being introduced through the Suez Canal from the Red Sea. Over the previous decade, Amphistegina spp. has colonized the eastern part of the Mediterranean Sea including the Egyptian and Libyan coasts, but the present southern limit in the Mediterranean Sea is along the southern Tunisian coast. However, this limit has never clearly been defined, and existing models predict an expansion along the entire Tunisian coastline. The Gulf of Gabes, in the southern part of Tunisia, is heavily polluted by local phosphate industries that discharge untreated waste directly into the sea. Amphistegina spp. is sensitive to water quality and marine pollution. Based on our surveys and recent investigations, the present distribution area of Amphistegina spp. along the south Tunisian coast includes the coastline east of Djerba Island, located in the Gulf of Gabes. Possible limiting factors for Amphistegina spp. expansion in the Gulf of Gabes may be the unfavourable environmental conditions generated by the phosphate industry. Kateb, Akram El; Stalder, Claudio; Stainbank, Stephanie; Fentimen, Robin; Spezzaferri, Silvia
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Though halophytes are naturally adapted to salinity, their salt-tolerance limits are greatly influenced by their provenance and developmental stage. In the present study, physio-biochemical responses of two Tunisian ecotypes of the oilseed coastal halophyte Cakile maritima (Brassicaceae) to salinity (0–400 mM NaCl) were monitored during germination and vegetative growth stages. Tabarka and Jerba seeds were collected from humid or arid climatic areas, respectively. Plant response to salinity appeared to depend on the ecotype and salinity levels. Increasing salinity inhibited germination process. Jerba seeds were found to be more salt tolerant than the Tabarka ones. At the autotrophic stage of growth and under salt-free conditions, Jerba was less productive than Tabarka (in terms of dry matter accumulation), but plant biomass production and leaf expansion (area and number) of the former ecotype were progressively improved by 100 mM NaCl, as compared to the control. In contrast, at the same salt concentration, these parameters decreased under increasing salinity in Tabarka (salt sensitive). Leaf chlorophyll content was reduced at severe salinity, but this effect was more conspicuous in the sensitive Tabarka plants. Na+ contents in the Jerba and Tabarka leaves collected from the 400 mM NaCl-treated plants were 17- and 12-fold higher than in the respective controls. This effect was accompanied by a significant reduction in the leaf K+, Mg2+ and Ca2+ contents, especially in the salt-treated Tabarka. A significant accumulation of proline and soluble carbohydrates in leaves was found during the period of intensive leaf growth. These organic compounds likely play a role in leaf osmotic adjustment and in protection of membrane stability at severe salinity.
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Given the growing interest of consumers worldwide in safe, healthy and good quality olive oil, the present study aimed to investigate a number of Tunisian virgin olive oil varieties in an attempt to procure physico-chemical characteristics of interest to the local and global olive oil industry, particularly in terms of variety and area of cultivation. Eight samples collected from Chetoui, Chemlali, Zarrazi, and Zalmati Tunisian cultivars located at Sfax, Thibar, Zarzis, and Jerba were employed. Various physic-chemical parameters were investigated, including free acidity, peroxide value, UV absorption, pigment concentrations, oxidative stability, fatty acid composition, phenolic compounds and sterols. The findings revealed high heterogeneity within and between the varieties. The Chemlali Jerba" and Zarrazi oil samples showed high oleic acid and low linoleic acid concentrations, rich phenolic compounds, and high stability. The sterols fractions in Chemlali Sfax, Chemlali Jerba, and Zalmati olive oils displayed high levels of β-sitosterol, campesterol, and ∆-5-avenasterol. Overall, the olive oil from Chemlali Jerba presented higher levels of natural antioxidants and oxidative stability. Its chemical composition was also noted to be particularly interesting in terms of fatty acid contents, minor components, and antioxidants, namely sterols, tocopherols, carotenoids, and phenolic acids.
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