Changes in biodeterioration patterns of mural paintings: Multi-temporal mapping for a preventive conservation strategy in the Crypt of the Original Sin (Matera, Italy)

Multi-temporal investigation of biodeterioration patterns (BPs)in cultural heritage sites is crucial for the development of effective management plans. Here, microscopy and biomolecular methods were employed to analyze the BPs, which took place in the Crypt of the Original Sin (Italy)over a wide temporal scale, i.e., from 2001 to 2017. Before restoration interventions, performed in 2002–2003, a variety of BPs was observed, including green patinas (Chlorophyceae), brown-black patinas (Cyanobacteria), rosy discolorations (Actinobacteria)and some colonization by lichens, mosses and ferns. Restoration included biocide treatments as well as structural interventions causing environmental modifications of the site. To interpret the ecological relationships between environmental factors and temporal changes, we combined the analysis of ecological information on the various BPs with the results of a multivariate statistical analysis. Using BPs as bioindicators, humidity maps of the plasters were generated and water infiltration paths reconstructed. Several years after biocide application, a significant reduction of BPs was observed, together with limited colonization by dematiaceous and meristematic fungi. Our observations demonstrate the usefulness of combining structural and environmental interventions for an effective restoration strategy; these interventions reduced the moisture levels of the walls, consequently reducing biological colonization. Moreover, our findings suggest that monitoring BPs during time can be of guidance in the long-term maintenance of cultural heritage, and provide an evidence-based model for preventive interventions and biocide treatments.