## 3 Results
platensis_ cells in Zarrouk medium (**B**), _Nostoc_ sp. cells in BG-11 medium (**C**). Controls: results of cultivation of cells without PFC and with 1 g/L glycerol are marked by a blue dotted line (**A**), and results of cultivation without both PFCs and glycerol are marked by a red line (**A–C**). The maximum and lowest values of average rate of biomass accumulation were found for _A. platensis_ and _Nostoc_ sp. cells, respectively (Figure 2). In a standard growth medium without additional additives, an increase in the concentration of perfluorohexane, polyether I or polyether II by 2 times from 0.5% to 1% (\(p/v\)) was accompanied by a slight increase (up to 8%) in the concentration of the accumulated biomass of each of the studied phototrophs. It was noted that by 72 h of cultivation in the presence of a PFC, the level of intracellular ATP concentration in phototrophic cells decreased slightly under experimental conditions (Table 1). It was found that when 1 g/L glycerol is introduced into the growth medium with _C. vulgaris_ cells as an additional component for mixotrophic nutrition, an increase in the rate of biomass accumulation by 9-32% is possible. This effect was most clearly expressed when glycerol was combined with polyether I (Figure 1). This fact suggests that the replacement of the Tamiya medium with wastewater containing an organic food source will contribute to an increase in the rate of biomass accumulation of _C. vulgaris_ microalgae cells. Analysis of Figure 2A suggests that in the case of simultaneous ingress into water bodies of sources of heterotrophic nutrition (organic substances) and substances with a gas transport function, a particularly intensive growth of phototrophic microorganisms should be expected, which is important for forecasting the development of ecosystems. _C. vulgaris_ microalgae cells were selected for further studies, as they are most often used as participants in biosystems for wastewater treatment, and they can also be present in fresh and salty reservoirs and in soil; they can also be part of aerobic active sludge [49]. Commercial perfluorohexane, which is already being produced in industry and is actively used in various fields as a refrigerant, fire-extinguishing agent, component of dielectric media, solvent and foam-blowing agent [50], and polyether II were used as PFCs from among the studied ones, as in the presence of this PFC, the maximum rates of accumulation of phototrophic biomass were noted. Effect of PFC on the Characteristics of Chlorella Biomass Accumulation in Presence of Immobilized Inoculum under Conditions of Periodic Cultivation in Wastewater  
The toxicity analysis of the studied PFCs, carried out using bioluminescent bacterial cells, confirmed the presence of toxicity in all media with a content of 1% (\(p/v\)) PFC. The level of bioluminescence in cells exposed in the analyzed media samples decreased by 20-97% for 0.5 h depending on the type of PFC. Perfluorodecalin turned out to be the most toxic for these cells. Despite the fact that PFCs and their derivatives are actively used in medicine, the presence of cytotoxicity with PFCs is generally consistent with the literature data [51; 52; 53]. The unique properties of the C-F bond and F-F interactions in PFC structures require increased attention to such compounds in the direction of minimizing the possibility of their ingress into the environment [53]. However, such a negative effect can manifest itself in relation to certain microorganisms, according to the data obtained with phototrophs (Figures 1 and 2), and bioluminescent cells were used for the current control of changes in the toxicity of the media implemented in the work because they are sensitive to PFC presence at a certain concentration (Figure S1). To study the process of accumulation of suspended biomass of _C. vulgaris_ microalgae, an immobilized inoculum was used as a concentrated form of stabilized cells and as a model of a self-stabilizing ecosystem that can be formed naturally by the phototrophs.