Accumulation and toxicological effects of cadmium, copper and zinc on the growth and photosynthesis of the freshwater diatom Planothidium lanceolatum (Brebisson) Lange-Bertalot: A laboratory study

Studies on toxicity and tolerance of cadmium (Cd), copper (Cu) and Zinc (Zn) in the diatom Planothidium lanceolatum (Brebisson) Lange-Bertalot (P. lanceolatum) were conducted by short-term bioassays using cell density, mortality and photosynthesis apparatus parameters. Results showed that the growth of the diatom was acutely sensitive to high metal concentrations in the order: Cd>Zn>Cu. Also, the IC50 calculated for this diatom are 0.25; 0.35 and 0.62 mg.L-1 for Cd, Zn and Cu, respectively. The statistical analysis showed that there was a significant effect on Fv/Fm and on chlorophyll-a of P. lanceolatum at Cd, Zn and Cu concentrations of >0.1; >0.2 and >0.4 mg.L-1, respectively, showing that photosynthesis is more affected then growth. Nevertheless, the diatom is tolerant to these metals in comparison with other works and most tolerant to Cu because the accumulation of this element was found to have the greatest affinity for the P. lanceolatum cells. Thus, this diatom widely available could be used as an economic biosorbent cheap material for the removal of these ions especially Cu from Tensift River waters. Further studies are needed to increase the biosorption capacities of biomass and develop appropriate biological technologies applicable in the wastewater treatment.