Evaluation of biodeterioration in the UNESCO site Etruscan Necropolis of Tarquinia

The Etruscan tombs of Tarquinia (Italy), listed as a UNESCO World Heritage Site in 2004, are hypogeal environments characterised by the presence of fine and precious wall paintings. Being carved in rock, these environments host a microbial community that can compromise the conservation of these artworks in specific environmental conditions. Indeed, the literature reports how different fungal species, penetrating inside porous stone materials, can cause physical and aesthetic damage leading to the detachment of the paint film or to the production of pigments, respectively. Finally, it is known that some fungal strains can dissolve carbonate substrates as a result of the metabolic production of organic acids. Aware of these dynamics, in collaboration with the restorer in charge of the archaeological site, the microbial communities within some Etruscan tombs have been monitored for several years. Usually, a degradation phenomenon identified in these environments is the presence of black spots, which are often associated with the presence of black fungi. Through in vitro growth and metabarcoding analysis of these spots, several fungal strains were identified, highlighting some similarities with some European Paleolithic caves. The study of their metabolic activity showed that their presence does not threaten the conservation of artworks from a chemical and/or physical point of view. However, the production by some strains of melanin could affect the aesthetic fruition of mural paintings. These results suggest how a targeted assessment of the metabolic activity of microorganisms can help restorers choose whether and how to proceed with avoiding the biocide treatments. Very often, in fact, such treatments, besides being harmful to the environment and to the operator, are effective on some species, while constituting a carbon source for others, encouraging their proliferation. Each microbial community, in fact, is characterised by its own internal balance that must be preserved and maintained.