Aerobiological behavior of Paleolithic rock art sites in Dordogne (France): a comparative study in protected sites ranging from rock shelters to caves, with and without public access

Abstract

Microbial organisms can cause huge crises in decorated caves, as seen in emblematic sites such as Lascaux cave. The preservation of such sites involves understanding the healthy microbial behavior of caves before the damage occurs. Indeed, knowledge of normal cave behavior is a prerequisite to identifying potential imbalance. This study seeks to determine whether models of aerobiological behavior could be identified in several caves of different sizes, ranging from rock shelters to large caves that are open or closed to the public. Aerial rates of fungi and bacteria were monitored over 3 years in nine sites in Dordogne (France). This study revealed that in a context of caves where public visits were carefully managed, fungal and bacterial rates were more affected by the size of the caves than by the opening of sites to the visitors. The study confirmed that large caves can generally be described as “self-purifying caves” as they were strongly affected by the exterior environment at their entry but much less so at locations further inside the cave, while small caves can be described as “non-self-purifying caves” since they were strongly affected by the exterior environment throughout their whole length. The results also highlighted the difficulty to determine a limit value of microbial rates valid for all caves because of the specificities of each one.