The field monitoring of influential biodeteriogenic agents on the historic rock surfaces in Persepolis-UNESCO World Heritage Site

Cultural heritage has always been the focus of many civilizations and therefore, it needs to be preserved for future generations. From prehistoric times, when grandeur and beauty were the aims of architecture, stone was the most widely used durable material. Biodeterioration of the stone monuments, one of the most important causes for the loss of the cultural heritage, is defined as any undesirable change in the properties of a material caused by the action of biological agents such as fungi, bacteria, cyanobacteria, lichens and plants, as well as animals such as insects. The world heritage of Persepolis, for example, has been unprotected from biodeterioration for the centuries, and has unfortunately not been addressed during this time. The purpose of this study is to provide a new perspective on the study of the destructive biological factors affecting this historic site to provide a framework for future studies and serious consideration of the biological debate in conservation and restoration issues. Therefore, the presence of various factors possibly derived from the action of animals, vascular plants, mosses, fungi, lichens, green microalgae, and photosynthetic and non-photosynthetic bacteria were investigated. Based on objective observations, the presence of biodegradation factors affecting floors and the all sides of walls of various buildings in Persepolis was qualitatively investigated. Based on the results, the studied areas were classified into four classes with very high, high, medium and low risk. In addition to the initial estimate of biodiversity, the factors affecting the biodegradation of Persepolis were presented for the first time and the critical points for the presence of destructive factors were determined. Lichens exist throughout Persepolis and have proved useful in archaeological studies, since their growth can be chronologically employed to measure the age of rocks and indeed ancient monuments, their radial growth increasing logarithmically over time based on the assumed specific rate. In this study, the presence of lichens has been investigated from the perspective of biodeterioration, their presence at the microscopic scale can intensify the weathering and biodeterioration of the rock. Such action is not visible to the naked eye but leaves irreparable damage to the stone surface. It was estimated that this complex process at Persepolis is the result of more than 15 different Vascular plant species and 5 Non-vascular plant (mosses), 16 or 17 different species of birds, 3 to 5 species of snails and 2 to 4 species of reptiles and insects. It was shown that the establishment of a biomonitoring laboratory at Persepolis is the important task of studying the action of microorganisms since it is estimated that more than 20 strains of non-photosynthetic bacteria, more than 10 taxa of cyanobacteria, about 15 plants and mosses, more than 130 lichen species and 20 species of non-lichen fungi are involved in the biodegradation of Persepolis. The results are the estimative and provide the basis for more detailed studies to monitor the factors involved in biodegradation, which is one of the necessities of this World Heritage Site.