## 3 Results and Discussion
### Mapping Biodeterioration Patterns  
Anca limestone is a homogenous and pure white limestone with a relatively high proportion of CaCO\({}_{3}\) (<96.5%), characterized by low compressive strength and hardness, high porosity (20-27.2%) and capillary absorption (10-14%). Due to its easy workability, it was extensively used in the decoration of the built partimony, made famous for highly detailed carvings [37, 78]. These are the same features that make it highly susceptible to fungal colonization and an exceptional target for biodeterioration. Similarly, parameters such as nutrient and water content and intensive diurnal and seasonal microclimatic oscillations to which stone is subjected, have a strong influence on the ability of fungi to colonize and grow in this substrate [79].  
In general, microbial colonization initiates with a wide variety of phototrophic microorganisms, mainly cyanobacteria and algae [80, 81, 82]. The accumulation of photosynthetic biomass provides an excellent organic nutrient base, supporting the subsequent establishment and growth of heterotrophic communities [24, 83]. In damper areas, such biofilms tend to be green [24, 84], such as the ones found in samples L1 and L2 in this study. Both sampling points were located below the two main windows in Lemos Pantheon and biofilm development could be related to sunlight exposure and water infiltration due to poor insulation of the windows. Surface biofilms are embedded in extracellular polymeric substances (EPS), that act as a physical barrier that protects microorganisms, enabling the retention of water and minerals and maintaining a more stable temperature and humidity [83]. Such favorable conditions tend to hold a higher diversity.  
However, the establishment of heterotrophic communities on rocks is possible even without the pioneering participation of phototropic organisms and, according to [PERSON] et al. [85], may in fact facilitate the subsequent growth of photosynthetic populations. In many cases, fungi are the first colonizers of stone surfaces [86, 87], particularly rock black fungi, since they can survive and thrive in dry conditions, with a low requirement of nutrients and energy, and are less susceptible to seasonal variations [88]. Besides the aesthetic alterations, these fungi can induce a chemical deterioration. However, the most relevant damages are believed to be due to a mechanical action, causing a breakdown of  
Figure 11: Co-occurrence network displaying the overlap of the cultivable species between the different culture media used for fungal isolation.  
the stone matrix [89]. Our L3 sample, characterized by the presence of black discoloration, was the driest and darkest sampled spot with visible mineral disintegration, found behind one of the tomb chests.  
The last sampling site (L4) was severely affected by salt damage. Salt decay is closely related to the petrophysical properties of stone, such as pore structure and other mechanical properties. Located near the Pantheon floor, due to capillary rise, water adsorption and condensation, probably from standard cleaning activities, favored efflorescence formation [90]. This precipitation process is a serious threat to the stone structure because salt occupying larger pores produces very high pressure, resulting in cracking, powdering, flaking, and material loss [91]. This salty micro-niche constitutes a suitable habitat for halophilic/halotolerant fungi, which, in conjunction with water impact, enhance the deterioration processes [92].