Spectrophotometric monitoring of surfaces in show caves as a part of management plans for controlling lampenflora growth

Abstract

deprived humid environments, such as mines, tunnels and catacombs, can support visible growth of microbial mats, with photoautotrophs as the dominant group of organisms. Photosynthetic pigments of aerophytic cyanobacteria and eukaroytic algae impose a greenish patina upon surfaces to which – with other community members – they adhere strongly. For example, sequencing of lampenflora DNA from the Škocjan Caves, Slovenia, UNESCO World Heritage Site, revealed a relative dominance of Cyanobacteria (~70%) among prokaryotes, over Proteobacteria (~10%), Bacterioidetes (~10%) and other groups that represented the remaining ~10% (Planctomycetes, Firmicutes, Acidobacteria, Chlamydiae, Verrumomicrobia, Actinobacteria). Diverse eukaryotic algae, fungi, flagellates and amoebozoans were also identified within the community. These “human induced diversity hotspots” in caves are responsible for the biodeterioration of colonized surfaces that is a common result of the synergistic effects of phototrophs and heterotrophs. When sites become colonized by higher plants, such as mosses, liverworts and ferns in species succession, irreversible biodeterioration impact on rocks and speleothems becomes an even more urgent issue. Historical inscriptions and rock-art paintings are particularly sensitive to biodeterioration. Lampenflora also affects components of the cave fauna, which not only graze upon it, but also facilitate its dispersal to other parts of the caves. It can be considered a direct indicator for light eutrophication and of the available energy within the cave ecosystem. There is a need for appropriate monitoring to provide alerts that will prompt timely action against lampenflora before it starts to affect the substrate integrity irreversibly, attract excessive and unwanted fauna or become encrusted and armoured against subsequent treatment and removal. Such monitoring could also be expanded to help estimate the efficiency of lampenflora removal in caves where this is carried out routinely. Regular monitoring can facilitate the delimitation of zones within a cave on the basis of the local susceptibility to lampenflora colonization. Spectrophotometric survey of cave surfaces can cover all of the above-mentioned aspects without adverse effects on the surfaces. Such methods are used widely in the printing, automotive, food, cosmetic, paint, construction, paper and packaging industries, etc. In the field of cultural heritage, the technique is applied to measure the difference in appearance of historical material before and after treatment with different preservative, protective or consolidative materials. One feasible approach to colorimetric analysis is based on a chromacity system CIEL*a*b* (where L* stands for luminosity, a* being the red–green parameter and b* being the blue–yellow parameter). This system enables easy calculation of colour changes over time or between individual sites. Several sites in the show cave sections SPECTROPHOTOMETRIC MONITORING OF SURFACES IN SHOW CAVES AS A PART OF MANAGEMENT PLANS FOR CONTROLLING LAMPENFLORA GROWTH