Biodeterioration of wall paintings in caves of Murcia (SE Spain) by epilithic and chasmoendolithic micro algae

Abstract

Cave wall paintings in Murcia are of worldwide archaeological interest because they are some of the few surviving artistic testimonies of the socio-economic reality of European pre-history. However, in recent years an increase of the microflora around and occasionally covering the paintings partially or totally has been observed. In our study fifty-two algal taxa were identified, among which the Cyanophyceae predominated, followed by Bacillariophyceae, Xanthophyceae and Chlorophyceae. Extreme values of the Photosynthetic Active Radiation, relative humidity and temperature are presented for each taxon in these cavelike environments. Epilithic and chasmoendolithic microalgal growth was found to be involved in the deterioration of the substrate. The algae were observed to grow in three types of formation (designated mat, patina and crust) that varied in colour from grey to black, passing through green, yellow, brown, pink and red. Besides biological, chemical and physical deterioration, the cave paintings have also suffered human intervention. This first diagnosis should be followed up by research into the best way of protecting the cave paintings from damage caused by microalgal growth.