Screening of trace metal elements for pollution tolerance of freshwater and marine microalgal strains: Overview and perspectives

Microalgae represent a putative solution to decontaminate metal polluted aquatic sites (phycoremediation). Seven different freshwater and seawater microalgal strains (Nannochloropsis sp., Dunaliella sp., Phaeodactylum sp., Chlorella sp., Isochrysis sp., Euglena sp. and Chlorogonium sp.) were exposed to five metals (Cu, Zn, As (III), Fe and Ni) at three concentrations each, simulating highly polluted sites. The experiment was conducted for a week; the survival ability of each strain and the photosynthetic pigments content (chlorophyll a, b and carotenoids) were evaluated, together with the Optical Density of each culture, pH, growth rate and biomass. Results highlighted different resistance patterns towards metals characterizing each algal strain, and the tolerance of all the microalgal strains towards arsenite. For the first time, the metal resistance pattern of Chlorogonium sp. was evaluated. Finally, our Euglena sp. and Dunaliella sp. strains were considered among the most promising organisms for phycoremediation of freshwater and seawater polluted sites respectively.