## 4 Discussion
### Correlation of Lithobitons with Salt Efflorescence  
The presence of _P. album_ is well documented and strongly correlated with soluble salt efflorescence [44, 71, 72]. Additionally, _P. album_ has been isolated from calcium salts such as oxalate, carbonate, and chloride [44, 73, 74]. This organism is known for its ability to produce various extracellular enzymes, such as protease, alpha-amylase, esterase, phosphatase, lipase, and chitinase. The functionality of these enzymes under high salinity conditions may account for the successful colonization of monuments affected by salt crystallization [44].  
Our PCA results indicated an association between the white turf and NO\({}_{3}\)\({}^{-}\) and NO\({}_{2}\)\({}^{-}\) (Figure 7). Indeed, the correlation between C\({}_{2}\)O\({}_{4}\)\({}^{2-}\) and NO\({}_{2}\)\({}^{-}\) may indicate organic matter degradation or microbial activity. Oxalate is often associated with biological processes [75],whereas nitrite is an intermediate in the nitrogen cycle, particularly under reducing conditions [76]. Moreover, fluoride is known to have antimicrobial properties. The source of this ion can be attributed to the capillary rise of groundwater rich in dissolved salts from the ground. The primary contributors to fluoride contamination in soil are industrial effluents, natural weathering of rocks, and atmospheric deposition [77].  
The occurrence of a pink discoloration in area S\({}_{6}\) is strongly associated with the development of a complex halophilic bacterial community, consistent with previous observations in salt-affected heritage environments [78; 79; 80; 81; 82]. These pinkish areas exhibited low CaSO\({}_{4}\) and high NaCl content, which, according to ion chromatography data, accounted for up to 72% of the total soluble salts (S\({}_{4a}\) Figure 6b,c and Figure 7). The origin of these salts can be attributed to multiple sources, including the capillary rise of groundwater through porous wall structures and subsequent evaporation-driven crystallization, as well as anthropogenic inputs such as the seasonal application of road deicing salts [83]. The microbial strains identified in these areas consistently exhibit halophilic adaptations, particularly to NaCl, as reported in similar studies [45; 48; 54; 55; 56; 58]. Most of these taxa are commonly found in soil ecosystems, especially within rhizosphere communities of higher plants [45; 46; 47; 48; 49], suggesting a likely pathway of colonization via water infiltration processes. Such infiltration mechanisms have been previously recognized as effective vectors for microbial transport in porous substrates [84; 85; 86], wherein cells may be transported by both the convection of aqueous-phase organisms and the generation of new aqueous phases. An analogous scenario was reported by [PERSON] [87], where rhizospheric microbial communities from the surrounding environment were conveyed into the chamber of an Etruscan tomb, re-establishing microbial colonization on painted surfaces post-cleaning. These findings corroborate the hypothesis that environmental water fluxes and salt dynamics act synergistically to facilitate microbial persistence and recolonization on wall paintings.