A strategy to potentiate Cd phytoremediation by saltmarsh plants - autochthonous bioaugmentation

The recovery of estuarine environments is in need. Phytoremediation could be a valid option to reduce pollution while preserving natural biodiversity. In this work, estuarine sediments colonized by Juncus maritimus or Phragmites australis were spiked with cadmium in the absence and in the presence of an autochthonous microbial consortium resistant to the metal. The aim of this study was to increase the potential for cadmium phytoremediation that these two halophyte plants have shown. Experiments were carried out in greenhouses with an automatic irrigation system that simulated estuarine tidal cycles. After 2 months, Cd concentration in P. australis stems increased up to 7 times when the rhizosphere was inoculated with the microbial consortium. So, P. australis phytoextraction potential was increased through autochthonous bioaugmentation. As for J. maritimus, up to 48% more Cd (total amount) was observed in its belowground tissues after being subjected to autochthonous bioaugmentation. Therefore, the phytostabilization potential of this plant was promoted. For both plants this increase in cadmium uptake did not cause significant signs of toxicity. Therefore, the addition of autochthonous microorganisms resistant to cadmium seems to be a valuable strategy to potentiate phytoremediation of this metal in saltmarshes, being useful for the recovery of moderately impacted estuaries. This will contribute for an effective management of these areas. Research on this topic regarding estuarine ecosystems, especially saltmarshes, is, to our knowledge, inexistent.