RESUMO
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.
RESUMO
The effect of light, copper ions, copper oxide nanoparticles on the change in the structural, functional, cytometric, fluorescent parameters of coccolithophore Pleurochrysis sp. was investigated. The culture Pleurochrysis sp. was represented by two cell forms: (1) covered with coccoliths; and (2) not covered, the ratio of which depends from growth conditions. An increase in light from 20 to 650µEm-2 s-1 led to a decrease in the concentration of cells covered with coccoliths from 90 to 35%. With an increase in light, the decrease in the values of variable chlorophyll a fluorescence was observed, a decrease in the chlorophyll concentration was noted, and an increase in cell volumes and their granularity due to coccoliths 'overproduction' was recorded. A tolerance of Pleurochrysis sp. to the effect of copper was registered, both in the ionic form and in the form of a nanopowder. This is probably due to the morphological (presence of coccoliths) and physiological (ligand production) peculiarities of species. Copper did not affect the ratio of cells covered with coccoliths; its value was about 85%. Growth inhibition, a 2-fold decrease in the intracellular chlorophyll content, a decrease in F v /F m , and a pronounced cell coagulation were recorded at the maximum Cu2+ concentration (625µgL-1 ). The mechanical effect was registered of CuO nanoparticles on the surface of Pleurochrysis sp. coccosphere, which results in the emergence of destroyed and deformed coccoliths. A hypothesis is proposed considering the protective function of coccoliths acting as a barrier when the cells are exposed to nanoparticles and copper ions.
