Multi-metal bioaccumulation ability of <i>Sesuvium portulacastrum</i> modulated by salinity in a high metal chelating substrate

Halophytes are known to be potential phytoremediators of metal-contaminated saline soils. <i>Sesuvium</i> portulacastrum (L.) L., has been reported to accumulate metals and is a candidate for metal decontamination in saline conditions. Here, we aimed to assess the impact of salinity on the ability of S. postulacastrum present in New Caledonian estuaries to extract multiple metals under conditions that facilitate the understanding of the plant’s extraction effectiveness. <i>S. portulacastrum</i> was cultivated in vermiculite and was watered twice a week with various concentrations of NaCl alone or combined with two concentrations (M1 and M2) of a multi-metal mix containing Ni, Co, Cr, and Mn. The results showed that shoot growth was at its maximum in the presence of 0 and 200 mM NaCl. At this last salt concentration, the M1 metal level in the substrate had no significant effect, but M2 decreased plant growth drastically. However, the total metal accumulation in shoots and roots was the highest under M2 multi-metal exposure. <i>S. portulacastrum</i> accumulated relatively high levels of metals in roots under varying salinity conditions. <i>S. portulacastrum</i> from the estuaries of New Caledonia exhibits significant potential for the phytostabilization of metals, even as salinity and metal concentrations increase in its growth areas. The ability of <i>Sesuvium</i> portulacastrum, and more generally halophytes, to accumulate and tolerate combinations of metals in varied salinity conditions has been very poorly assessed until now, and this is the first study of this type for <i>S. portulacastrum</i> from New Caledonian estuaries. Three of the four metals tested here (Co, Cr, and Mn) were very poorly or not studied for these capabilities, the main metals reported in the literature being Cd, Cu, Zn, and Pb. The metal combination doses showed original interactions with salinity, changing with concentrations.