The hypogeous roman archeological museum of Positano: study of the evolution of biological threaten and development of adequate control protocols

Hypogea are natural or artificial spaces located underground often of great interest from an anthropological, archeological, religious, artistic, or historic point of view. Due to their features, these environments usually present conservative problems and biological colonization could be considered as one of the main threats. The present three-year study was carried out by specialists of the Central Institute for Restoration of Rome (ICR) in the hypogeous site preserved in the Roman Archeological Museum of Positano (Positano MAR) and focused on characterizing biological alterations present on the mural paintings; setting up efficient strategies and protocols for biodeterioration control; and monitoring the efficacy of direct and indirect interventions. Patinas with different morphologies were analyzed through microscopic observations, cultural analyses and next-generation sequencing. The results proved that the alterations comprised a great variety of microorganisms forming very distinct communities, differently distributed over space and time. The main taxa represented were bacteria of phyla Pseudomonadota and Actinomycetota, fungi belonging to the genus Fusarium and Gliocladium, and algae of the genus Chlorococcum. Preservation protocols were set up considering the alterations’ composition and included the application of biocides, limiting daily temperature changes, decreasing illuminance values on painted surfaces, and the screening of natural light sources.