In the present study, changes were determined in morphological, structural-functional, and fluorescent parameters of Prorocentrum cordatum with the addition of CuO nanoparticles (NPs) and copper ions (CuSO4). A stimulating effect of low Cu2+ concentrations (30 μg L-1) on algal growth characteristics was observed. Higher Cu2+ concentration of 60-600 μg L-1 and CuO NPs concentration of 100-520 μg L-1 inhibited algal growth. Ionic copper is more toxic to P. cordatum than NPs. After 72 h of algae cultivation in the medium supplemented with CuSO4 and CuO NPs, EC50 values (calculated based on cell abundance) were of 60 and 300 μg L-1 (in terms of copper ions), respectively. Reduction in algal growth rate is due to disruption in cell cycle, changes in nuclear morphology, chromatin dispersion, and DNA damage. The studied pollutants slightly affected the efficiency of P. cordatum photosynthetic apparatus. Addition of the pollutants resulted in an increased production of reactive oxygen species (ROS). At a concentration of Cu2+ of 120 μg L-1 and a concentration of CuO NPs 0-300 μg L-1 of CuO NPs increase in ROS production is short-term with a decrease at later stages of the experiment. This is probably due to the activation of antioxidant mechanisms in cells and an increase in the concentration of carotenoids (peridinin) in cells. The high values of ROS production persisted throughout the experiment at sublethal copper concentrations (400-600 μg L-1 of CuSO4 and 520 μg L-1 of CuO NPs). Sublethal concentrations of pollutants caused restructuring of cell membranes in P. cordatum. Shedding of cell membranes (ecdysis) and formation of immobile stages (temporary or resting cysts) were recorded. The pronounced mechanical impact of NPs on the cell surface was observed such as-deformation and damage of a cell wall, its "wrinkling" and shrinkage, and adsorption of NP aggregates.
Keywords: Cell morphology; Copper; CuO nanoparticles; EC50; Prorocentrum cordatum; Reactive oxygen species.
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