Comparative Evaluation of the Effect of Copper Oxide and Copper Sulfate Nanoparticles on Structural and Functional Characteristics of Thalassiosira weissflogii under Conditions of Enrichment Cultivation

The effect of copper oxide nanoparticles (500, 1000, 2000 μg/L) and copper ions (37.5, 75, 150 μg/L) on the morphological, structural-functional, and fluorescent parameters of diatom microalgae Thalassiosira weissflogii under conditions of long-term cultivation was studied. It was shown that copper in ionic form is more toxic for this microalgae species than in the form of a nanooxide. The nature of the effect of copper in ionic and nanoform on cells Thalassiosira weissflogii has both similarities and significant differences. The difference in the effect of the studied toxicants on the growth of algae and the performance of photosynthetic apparatus was revealed. The addition of copper ions into the cultivation medium led to long lag phase during the initial stage of the experiment, followed by the restoration of growth on days 3–6 of exposure. An increase in the concentration of copper oxide nanoparticles in the medium caused inhibition of algae growth without a pronounced lag phase. With an increase in the concentration of Cu 2+ in the culture medium, a decrease in the quantum efficiency of light energy utilization by the PS II photosynthetic complex and the maximum relative electron transport rate were observed, while copper oxide nanoparticles had an insignificant effect on the efficiency of the photosynthetic apparatus of Thalassiosira weissflogii . With an increase in the concentration of copper, both in the ionic form and in the form of nanooxide, increase in cell volume, changes of cell shape and granularity, an increase in the production of reactive oxygen species, suppression of enzymatic activity and a decrease in autofluorescence values of individual cells in the red region of the spectrum were observed.