Lotfi Rabaoui

Heavy metal contamination and ecological risk assessment in the surface sediments of the coastal area surrounding the industrial complex of Gabes city, Gulf of Gabes, SE Tunisia.

In the present study, the concentrations of 6 trace metals (Hg, Cd, Cu, Pb, Cr and Zn) were assessed in the surface sediments of the central coastal area of Gabes Gulf to determine their contamination status, source, spatial distribution and ecological risks. The ranking of metal contents was found to be Zn>Cd>Cr>Pb>Cu>Hg. Correlation analysis indicated that Cd and Zn derived mainly from the Tunisian Chemical Group phosphogypsum. The other pollutants may originate from other industrial wastes. Metallic contamination was detected in the south of chemical complex, especially in the inter-harbor zone, where the ecological risk of surface sediments is the highest, implying potential negative impacts of industrial pollutants. The spatial distribution of pollutants seems to be due to the effect of harbor installations and coastal currents. The metallic pollution status of surface sediments of Gabes Gulf is obvious, very worrying and requires rapid intervention.

Comparative morphometric study of the invasive pearl oyster Pinctada radiata along the Tunisian coastline.

In order to study the relative growth of the pearl oyster Pinctada radiata in Tunisia, a total of 330 individuals of this species were collected from six sites along the Tunisian coastline. Quantitative measurements of collected oysters were conducted for shell height, shell length, shell width, hinge length, height and width of the nacreous part and wet weight. The size structure of the sampled populations was described and the relative growth between different morphometric characteristics was estimated as allometric growth lines for the six P. radiata samples. It appeared that the majority of examined samples were dominated by large individuals that exceed a shell height of 42 mm. The maximum size (100.5 mm), recorded in Bizerta lagoon, is bigger than that recorded elsewhere in particular in the Red Sea. Size distribution analysis also showed that the majority of P. radiata samples were dominated by two or more size groups. Differences of allometric regression were found between the examined samples for the tested relationships. Moreover, the Factorial Discriminant Analysis, coupled with Ascending Hierarchic Classification, classified the sub-populations according to geographic locations.

Metal bioaccumulation in two edible cephalopods in the Gulf of Gabes, South-Eastern Tunisia: environmental and human health risk assessment

Samples of Octopus vulgaris and Sepia officinalis were collected from four areas in the Gulf of Gabes, south-eastern Tunisia, and their edible tissues (mantle and arms) were analyzed for cadmium, copper, mercury, and zinc. While the concentrations of metals showed significant differences between the sampling sites, no differences were revealed between the tissues of the two species. The spatial distribution of metals analyzed showed similar pattern for both tissues of the two species, with the highest concentrations found in the central area of Gabes Gulf, and the lowest in the northern and/or southern areas. From a human health risk point of view, the highest values of estimated daily intake, target hazard quotient, and hazard index were found in the central area of Gabes Gulf. Although the results of these indices were, in general, not alarming, the health risks posed by the consumption of cephalopods on local consumers cannot be excluded.

Development and characterization of bioactive edible films from spider crab (Maja crispata) chitosan incorporated with Spirulina extract.

Active food packaging films based on crab chitosan and Spirulina extract (SE) were developed. The effects of the SE incorporation at different levels on physical (color, opacity water vapor and oxygen permeability) and mechanical (tensile strength and elongation at break) properties of chitosan films were investigated. FTIR was carried out to observe the potential modifications of the chitosan films when incorporated with SE. The obtained results suggested that incorporation of SE into chitosan films improved mechanical and barrier properties. The antioxidant activity of the chitosan/SE films was characterized by means of three different analytical assays (DPPH, FRAP and FIC). Crab chitosan edible films containing SE showed higher antioxidant activity, regardless concentrations and methods assayed. Furthermore, the antioxidant activity occurred in a concentration-dependent manner. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, Salmonella typhimurium, Bacillus subtilis and Bacillus cereus. The chitosan/SE films were more effective (p<0.05) against five of the seven tested bacteria. The obtained crab chitosan edible films incorporated with SE showed great potential to be used for active food packaging due to its excellent antioxidant and antibacterial activities.

Accumulation of Carbonates Contributes to Coastal Vegetated Ecosystems Keeping Pace With Sea Level Rise in an Arid Region (Arabian Peninsula)

This research was supported by a project funded by Saudi Aramco and baseline funding from King Abdullah University of Science and Technology (KAUST). O. S. was supported by an ARC DECRA (DE170101524). Funding was provided to PM by the Generalitat de Catalunya (grant 2014 SGR‐1356) and an Australian Research Council LIEF Project (LE170100219). AAO was supported by a PhD scholarship from Obra Social “LaCaixa”. This work is contributing to the ICTA ‘Unit of Excellence’ (MinECo, MDM2015‐0552). We thank A. Qasem and P. Priahartato, Saudi Aramco, for support and advice on sampling design; R. Lindo, R. Magalles, P. Bacquiran, S. Ibrahim, and M. Lopez, at the Marine Studies section of the Center for Environment and Water of King Fahd University of Petroleum and Minerals; and Z. Batang and staff from the Coastal and Marine Resources core lab at KAUST for help with sampling. We thank I. Schulz, N. Geraldi, K. Rowe, S. Roth, M. Ennasri, D. Prabowo, and I. Mendia for help with laboratory analyses. We wish to thank the two anonymous reviewers, as well as Editor in chief M. Goni, for their precious comments/suggestions for the improvement of the manuscript. The data sets, including 14C and 210Pb data, CaCO3 concentration values, porosities, and CaCO3 depth profiles for all cores, are available in the open repository Pangaea (Saderne et al., 2018; https://doi.pangaea.de/10.1594/PANGAEA.887043).

Characterization of phosphate rock and phosphogypsum from Gabes phosphate fertilizer factories (SE Tunisia): high mining potential and implications for environmental protection

Since the establishment of the coastal industrial complex in Gabes city (Gulf of Gabes, SE Tunisia), hundred million tons of untreated phosphogypsum have been discharged in the open sea causing serious environmental problems. To better understand the dynamic and behavior of phosphate/phosphogypsum contaminants from raw ores to marine environment, a chemical, organic, mineralogical, and morphological characterization of phosphate rock and phosphogypsum was conducted using several sophisticated techniques. The chemical analysis showed that phosphate and phosphogypsum contain high loads of trace elements and that the transfer factors of pollutants varied from 5.83% (U) to 140% (Hg). Estimated annual flows of phosphogypsum contaminants into the marine environment ranged between 0.05 (Re) and 87,249.60 (F) tons. The phosphate rock was found to be formed by carbonate fluorapatite, calcite, dolomite, natural gypsum, quartz, calcite-Mg, apatite, pyrite, fluorite, and sphalerite-Cd and phosphogypsum by synthetic gypsum and sphalerite-Cd. The phosphate was found to be richer in organic compounds compared to phosphogypsum. Based on this work, the Tunisian phosphogypsum has a high mining potential and encourages the development of an economically beneficial and environmentally friendly phosphogypsum-treating industry.