## 5 Results and Discussion
### Microbiological Analysis
#### 5.3.2 Cultural Analysis
In the portions of the mosaic where the Rocima(tm) 103 biocide was used (one month before the microbiological sampling in correspondence to samples MRC2 and MRC5) (Figure 3), a good reduction in the microbial biomass was observed, although it has not been completely removed. For this reason, cultural analysis showed a recolonization even of scarce entity. In fact, single-celled algae and numerous bacteria have been isolated (Tables 4 and 5). The results achieved, thus, demonstrate that on one hand, the treatment with 2% of Rocima(tm) 103 was quite effective to eliminate the actual colonization, but on the other hand does not have long-term efficacy, allowing the recolonization of the mosaic _tesserae_. * According to the different types of materials identified, the sedimentary samples (i.e., white, pinkish and greyish _tesserae_), coming from the central area of the thermal bath having a mosaic floor, show more marked alteration forms compared to the _tesserae_ of volcanic origin (i.e., black). Unlike sedimentary samples, volcanic ones do not have superficial alteration layers, such as patinas. * By comparing the light colored and greyish _tesserae_ and all sedimentary rocks, it is possible to detect some differences in terms of alteration forms, mainly attributable to biological colonization. Many of these are replacement _tesserae_ and show superficial patinas with lower thicknesses than the original ones. * In some replacement _tesserae_, the bedding mortar is much more degraded than that found in some original _tesserae_. * As for the samples taken in the _caldarium_ room, including both brick, marble and mortar, they show an overall good state of conservation with slighter superficial patinas compared to those found in specimens sampled in the central compartment with mosaic. Additionally, the mortar is intact, well preserved and rich in fragments of cocciopesto that surely increased its resistance and limited the degradation. * Biological colonization resulted to be one of the main problems causing esthetical (coverage of surfaces), mechanical (endolithic colonization) and chemical deterioration patina formation and alteration layers ranging from 200 to 500 \(\upmu\)m depending on the nature of the colonized material. In fact, volcanic rock (dark _tesserae_) is less affected by biological attack, followed by compact sedimentary calcareous stone, while those stones with cracks and fissurations are affected not only by a biological patina on the surface but also by a colonization of endolithic microorganisms, mainly black fungi. The research represents a further milestone to better manage future restoration intervention, especially regarding the choice of the best cleaning procedures to carry out within the archaeological site. Suitable conservative procedures will allow protecting the stone materials against the degradation phenomena mainly related to the biological colonization, type of stones and exposure in the site. From this study, the need for periodical intervention (at least one before the starting of the vegetative period) with the use of classical biocide (e.g., Rocima(tm, 103) for the removal of already grown biomass, followed by the application of products that can slow down the regrowth, is clear. Conceptualization, M.F.L.R. ; methodology, M.F.L.R., M.R., C.E.U., F.D.L. ; formal analysis, M.R., N.R., S.A.R. ; investigation, M.R., N.R., S.A.R., A.S., A.B., C.E.U., F.D.L., A.A., L.R. ; resources, M.F.L.R. ; data curation, M.F.L.R., M.R. ; writing--original draft preparation, M.F.L.R., M.R., N.R. ; writing--review and editing, M.F.L.R., M.R., R.N., C.E.U., A.B. ; supervision, M.F.L.R. ; project administration, M.F.L.R. ; funding acquisition, M.F.L.R. All authors have read and agreed to the published version of the manuscript. This research is part of the POR Calabria FESR project \"NANOPROTECH\" (NANO PROtection Technology for Cultural Heritage) (24E07000380005). The authors declare no conflict of interest.