Dhouha Belhaj Sghaier

Halophytes are recognized for their adaptive capacity and potential applications in phytomanagement and ecosystem restoration. This study investigates the comparative physiology and antioxidant responses of two native halophytes, Caroxylon vermiculatum (L.) and Mesembryanthemum nodiflorum L., growing naturally in saline and metal-affected coastal environments. A comprehensive set of physiological and biochemical parameters was assessed, including macro- and microelements (Na, K, Ca, Fe, Zn, Cd), photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids), soluble sugars, and proteins. In addition, oxidative stress markers (hydrogen peroxide, H₂O₂, and malondialdehyde, MDA), enzymatic antioxidants (superoxide dismutase, SOD, catalase, CAT, and guaiacol peroxidase, GPX), and non-enzymatic antioxidants (total phenolics, flavonoids, and proanthocyanidins) were evaluated. Antioxidant activities, including DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and reducing power, were also measured. The results revealed clear species-specific adaptive strategies. Mesembryanthemum nodiflorum exhibited higher accumulation of Na and K, together with elevated levels of carotenoids and oxidative stress markers. This species showed translocation factors (TF > 1) for Na (~1.60) and K (~1.90), indicating efficient ion transport to aerial parts, while displaying low bioconcentration (BCF < 0.5 for most trace elements) and biological accumulation factors (BAF < 1), suggesting limited capacity for heavy metal accumulation. In contrast, Caroxylon vermiculatum showed higher concentrations of chlorophylls, carotenoids, phenolic compounds, flavonoids, and proteins, along with stronger superoxide dismutase activity. It also exhibited lower translocation of trace elements (TF < 1) and higher root retention of metals (BCF up to ~0.5), indicating a more effective exclusion and detoxification strategy. Overall, these findings demonstrate that M. nodiflorum relies on ion accumulation and translocation, whereas C. vermiculatum exhibits stronger ion regulation and antioxidant protection. Given the moderate BAF and BCF values observed, both species are more likely to contribute to phytomanagement through ion regulation and phytostabilization rather than efficient phytoextraction.

The pollution caused by microplastics (MPs) in marine sediments has been a concern of many researchers thanks to these substances’ persistence and potential ecological effects. To our knowledge, this study represents the first comprehensive investigation of MP contamination in marine sediments collected from multiple regions of the Mediterranean Sea, encompassing a wide bathymetric range from coastal areas to deep-sea environments, down to approximately 4000 m water depth. Sediment samples were taken from several sites in the Mediterranean and the northern Aegean Sea. Thanks to microscopic analysis, fragments and filaments were the dominant MP forms; their color and size varied, and the most frequent particle colors were red, transparent and blue. FTIR spectroscopy revealed diverse types of polymers, including polystyrene (PS), propylene (PP), ethylene–vinylacetate (EVA), polyamide (PA), and Acrylonitrile Butadiene Styrene (ABS) polymer. The ^1-H NMR analyses confirmed the presence of PA, EVA, PP, polyethylene (PE), and PS, thereby supporting the FTIR results. This spatial variability in polymer composition probably reflects both regional anthropogenic inputs and hydrodynamic factors affecting sedimentary deposits. These results detail the complex and generalized nature of MP contamination in Mediterranean sediments and offer a basis from which to start assessing ecological risks and developing targeted mitigation strategies.

Plastic and microplastic debris (MP) constitute the most important pollutants of the solid litter with a high risk of sediment accumulation. Posidonia oceanica (L.) Delile is the main marine seagrass of the Mediterranean Sea which forms immense underwater meadows and deposits of seagrass beds covering the facades of sandy beaches. They are formed by roots and rhizome fragments gathered in fibrous marine balls, called aegagropiles (EGs), having the ability to trap several pollutants from the beaches and mainly microplastic. The present study aims at evaluating microplastic contamination in aegagropiles collected from four locations along the Tunisian coast in the southern Mediterranean basin (two northern sites (S1 and S2) and two southern-central sites (S3 and S4). Microscopic analysis revealed that red and blue microplastics dominated at all sites, with black fibers and fragments being the most prevalent forms and yellow (S3) and transparent particles in S1, S2, and S4. Polymer identification conducted using nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR) detected microplastic types with contamination levels and microplastic accumulation variation among the four sites including polystyrene (PS) at sites S1, S3, and S4; ethyl vinyl acetate (EVA) at S1 and S3; polyethylene terephthalate (PET) at S1 and S2; and polyvinyl chloride (PVC) at S2 and S3. Our results highlight close relationships between anthropogenic activities, extensive plastic use, and elevated microplastic pollution in marine ecosystems, particularly in seagrass beds. These findings emphasize the importance of monitoring microplastic contamination to preserve the health of Mediterranean coastal environments.

Al stress is a serious environmental problem that affects plant physiology and biochemical processes and reduces productivity in the agricultural sector. This study is a comparative study between the antioxidant responses of two different halophyte species and focuses on two halophytes Arthrocnemum indicum and Tamarix gallica. Both halophytes species exposed to different concentrations of Al (200, 500, 800) µM alone or combined with NaCl (200 mM) and the effect of Al on oxidative damage and enzymatic and non-enzymatic antioxidant responses were determined. Our results demonstrated that Tamarix gallica was more tolerant to Al stress than Arthrocnemum indicum and this by a low level of MDA registered. In addition, T. gallica showed more marked antioxidant activities. However, salinity improves the tolerance of A. indicum by increased levels of glycine betaine and proline. Nevertheless, T. gallica is still more tolerant according to the tolerance index than A. indicum and this species is a favorable plant material to soils phytoremediation. T. gallica can be successfully used for phytostabilization of Al-contaminated saline soils

In order to evaluate the ecological risk generated by the heavy metals cumulation in salt-affected soils. The research was carried out in the halophyte Tamarix gallica which is known to thrive under harsh environmental occurrences. The main aim of this work was to study the tolerance and accumulation capabilities of Tamarix gallica under Arsenic, Aluminium and salt stress. Plants were cultivated in the presence of increasing concentrations of Al and As alone (200, 500 and 800 µM), or mixed with NaCl (200 mM). The results revealed that both metals altered the growth and development of T.gallica. Finding showed that the metals’ accumulation was dependent on the concentrations of the metals in the medium. Interestingly, while salt reduced As uptake, an augmentation in Al accumulation was observed. In addition, T. gallica demonstrated that APX was the predominant enzyme to scavenge excess ROS. However, SOD and GPX were sensitive to the metal, showing different behaviour in metal stress alone or combined with salt. Proline accumulated in a dose-dependent manner under Al and As stress, rather than lower or unchanged levels of glycine betaine. We also noticed a diminution in proline content caused by NaCl application while an increase in glycine betaine was remarked. On the other hand, the combined stress enhanced proline whereas unchanged levels of glycine betaine were observed. Finally, T. gallica demonstrated its potential to grow under elevated concentrations of As/Al and could be considered a suitable candidate for phytostabilization/ phytoremediation approach.