Evaluating environmental impact and remediation potential: Bioaccumulation and translocation of potentially toxic elements in three native halophyte species in the wetlands of the Bouregreg estuary in Morocco.

This study in the Bouregreg estuary examines the accumulation and seasonal variation of potentially toxic elements (PTEs) in three native halophytes: Halimione portulacoides, Salicornia perennis, and Spartina maritima. PTEs concentrations of cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), and vanadium (V), remained below known phytotoxic thresholds, showing high tolerance across all species. S. maritima showed the highest accumulation, likely due to habitat-related factors such as submersion duration and sediment conditions. Compared to a construction-period data, current findings show increased Cr and decreased Zn and Cu levels, especially in H. portulacoides, reflecting post-construction environmental changes. All species exhibited root-dominant metal accumulation. Bioaccumulation indices (bioaccumulation coefficient (BAC), bioconcentration factor (BCF), and translocation factor (TF)) confirmed species- and metal-specific strategies. For cadmium, S. maritima showed high accumulation (BCF >40, BAC >30), while S. perennis reached BAC values up to 26.5 with site-dependent uptake. Chromium was effectively translocated by S. maritima (TF > 1, shoot-soil r ≈ 0.98) and H. portulacoides (stem-soil r = 0.99), while S. perennis showed limited uptake despite strong correlations. Copper was excluded by S. maritima, but actively translocated by H. portulacoides and S. perennis (TF > 1). Zinc showed weak accumulation across species (BAC <1); S. maritima had strong shoot-soil correlations, while others showed efficient translocation but poor soil correlation. Vanadium was consistently translocated (TF > 1) with positive shoot-soil correlations across all species. Cadmium showed weak correlations with other metals, suggesting independent, possibly anthropogenic sources. In contrast, Zn, Cu, Cr, and V co-varied with species-specific patterns and peaked in summer, while Cd peaked in autumn, likely from senescence and site conditions. Overall, these findings provide new field-based evidence of halophyte tolerance and adaptive strategies, underscoring their dual-ecological role as bioindicators of contamination and as promising agents for phytoremediation in the Bouregreg estuary under ongoing urban pressures.