## 3 Results  
### Experiment 1: Selection of Methods Used for Assessing Photoautotrophic Growth on Plaster Coatings  
The results of biofilm cell enumeration, luminometric ATP measurement, chlorophyll \(a\) determination, and spectrophotometric color change evaluation performed on plaster coating samples after inoculation, at 14 and 28 days of incubation, are presented in Table 1.  
During a 28-day culture of microalgae on building materials, an increase in cell density was observed for all tested samples. At the beginning of the analysis (t = 0 days), no cells were observed in the measurement field of the hemocytometer. After 14 days of incubation, a significant increase in cell density was observed, with the highest value for the technical material MPGS (3.67 \(\times\) 10\({}^{7}\) cfu/cm\({}^{2}\)) and the lowest for S (2.00 \(\times\) 10\({}^{7}\) cfu/cm\({}^{2}\)). After 28 days of incubation, a further increase in the density of photoautotrophic cells per 1 cm\({}^{2}\) of all tested technical materials was observed. At the end of the analysis, the lowest density of cells on building materials was obtained for S (4.00 \(\times\) 10\({}^{7}\) cfu/cm\({}^{2}\)), and the highest density for MP (6.33 \(\times\) 10\({}^{7}\) cfu/cm\({}^{2}\)). For all times and all types of technical material, no cells were observed in the control samples. No chlorophyll \(a\) (chl-_a_) was detected for any of the control samples of the tested technical materials, regardless of the incubation time. During 28 days of the analysis, an increase in the concentration of chlorophyll a, produced by active microalgal cells, was observed on all tested building materials. After inoculation, the concentration of chlorophyll a in most of the analyzed samples was close to 0. After 14 days of cultivation, the chl-_a_ value slightly increased for three out of four tested plates, reaching the highest value for MPGS (0.28 mg/cm\({}^{2}\)). No growth in the chl-_a_ indicator was observed for the S coating type. After 28 days of incubation, a significant increase in the examined index was observed for all materials except for SGS. The highest chl-_a_ value was recorded for MP (0.44 mg/cm\({}^{2}\)), and the lowest for SGS (0.05 mg/cm\({}^{2}\)). Simultaneously, a semi-linear increase in ATP was observed for the MP, S, and SGS samples during the experiment. This trend was not observed for the tested MPGS coating type, showing the highest RLU values after 14 days of incubation. After the inoculation process, the mean ATP value per 1 cm\({}^{2}\) of the surface of the technical material was in the range of 1.19 \(\times\) 10\({}^{1}\)-1.41 \(\times\) 10\({}^{1}\) RLU. After 14 days of incubation, the highest value of the index, 1.13\(\times\)10\({}^{3}\), was recorded for MPGS, and the lowest for S (7.15 \(\times\) 10\({}^{1}\) RLU). It should be noted that the values recorded for the MPGS coating were disproportionally higher than for other types. After another 2 weeks of cultivation, the amount of ATP in the MPGS decreased to 2.82 \(\times\) 10\({}^{2}\) RLU, which was still the highest value among the tested materials on the 28 th day of the analysis. A similar level of ATP was noted for the material marked MP. The lowest value of the examined indicator was recorded for sample S, reaching 7.67 \(\times\) 10\({}^{1}\) RLU. For all tested materials, a trend of a significant increase in color change over time was observed. The mean color change was also visible after the inoculation process and was in the range of \(\Delta\)E = 1.61 \(\times\) 10\({}^{0}\) (S) \(\pm\) 1.91 \(\times\) 10\({}^{-1}\)-2.93 \(\times\) 10\({}^{0}\)\(\pm\) 1.03 \(\times\) 10\({}^{0}\) (MP) depending on the technical material type. After 14 days of incubation, the mean color change for all materials was significant and in the range of 5.97 \(\times\) 10\({}^{0}\)\(\pm\) 1.46 \(\times\) 10\({}^{0}\) (S)-1.32 \(\times\) 10\({}^{1}\)\(\pm\) 7.50 \(\times\) 10\({}^{-1}\) (MP).