## 3 Results  
### Biodeterioration Patterns  
The macroscopic observations of the Northern Pergola revealed that the biological colonization was more mature and complex on the north-facing side compared to the southern exposure. Apart from the visible discoloration, various multicolored, powdery, crusty and shrubby biocenoses were observed on the sandstone surfaces (Figure 1). Figure 1: General view of the Northern Pergola in winter from the southern (**a**) and the north-facing side (**b**). Samples that display different biodeterioration patterns (BPs) were taken (except sample no 2) from vertical surfaces and from a similar height from the ground (Figure 2). According to the scale used by [PERSON] et al. [33] both insolation and water availability of the analyzed samples were medium high. Based on these macroscopic examinations, eight different sampling sites from the northern exposition were selected for the diversity analyses. We observed various BPs [34] of the sandstone surfaces (Figure 2):  
* green biofilms (GB) in sites 6 and 7. * yellow biofilms (YB) with lichen crusts (LC) and mosses (M) in site no. 8. * mosses (M) in sites 1, 2, and 3. Figure 2: Architectural chart of the Northern Pergola at the Museum of King John III’s Palace at Wilanow with sampling locations (**a**), most important identified characteristic species of organisms inhabiting sandstone surfaces (**b**) and biodeterioration patterns of the sandstone surfaces (**c**). masses (M) with lichen crusts (LC) in site no. 4. lichen crusts (LC) in site no. 5. The most shadowed sites (sites 1, 2, and 3) were each covered with a continuous thick layer of masses, mainly _Tortula muralis_ and _Bryum caespiticium_ (Figure 2). The next two sites (sites 4 and 5) were mostly colonized by lichens _Protoparnelopsis muralis_ and _Lecanora dispersa_ (Figure 2) with traces of _Candelariella aurella_ and _Caloplac citrina_. The other sites were dominated by unicellular and filamentous algae (site 6), mosses (sites 7 and 8)-_Brachythecium rutabulum_, _Schistidium apocarpum_, _Bryum argenteum_, and _Homalothecium sericeum_ and lichens _Lecanora dispersa_ (Figure 2). The scanning electron microscopy (SEM) technique was used to visualize porosity and damages of the sandstone surfaces caused by microbial communities (Figure 3a). Detailed analyses of SEM images (Figure 3b) confirmed that organisms, including bacterial structures, are present on sandstone surfaces regardless of season. This is due to the adaptation of microorganisms to low temperatures, as well as the effect of climate warming. Figure 3: Scanning Electron Microscopy (SEM) images of lithobiontic organisms (red arrows) and of microorganisms (yellow arrows) inhabiting historical Pergola. SEM images of larger biofilm areas (**a**) and SEM images at higher magnification for biofilms samples analyzed in summer and winter (**b**). Nevertheless, microscopic observations (SEM images) of samples taken in winter as compared to summer samples allowed to visualize finer sediment structures in the analyzed material in samples 4-8. These differences can result from night frosts, which can affect both the weathering processes and the biodeteriogen consortia themselves, such as cell shrinkage. The visible bioenoses showed different appearances during winter and summer seasons not only in sites 4 and 5 inhabited by _Caloplaca citrina_-species known from their ability to produce yellow-red pigments [35]. They were distinctly green during summer while brownish and greyish colors were more common in winter (Figures 1 and 2). On the contrary, there were no pronounced changes in look of lichens. The composition of lichens also did not change within subsequent seasons. The visible color changes of BPs depending on the seasons became the starting point to determine their cause. Since Warsaw is one of the cities with the highest air pollution indexes in Poland, in the first stage we measured concentration of air pollutants in winter and summer.