Airborne microorganisms in Lascaux Cave (France)

International Journal of Speleology 43 (3) 295-303 Tampa, FL (USA) September 2014 Available online at scholarcommons.usf.edu/ijs/ & www.ijs.speleo.it International Journal of Speleology Off icial Journal of Union Internationale de Spéléologie Airborne microorganisms in Lascaux Cave (France) Pedro M. Martin-Sanchez1, Valme Jurado1, Estefania Porca1, Fabiola Bastian2, Delphine Lacanette3, Claude Alabouvette2, and Cesareo Saiz-Jimenez1* Instituto de Recursos Naturales y Agrobiología de Sevilla, IRNAS-CSIC, Apartado 1052, 41080 Sevilla, Spain UMR INRA-Université de Bourgogne, Microbiologie du Sol et de l’Environnement, BP 86510, 21065 Dijon Cedex, France 3 Université de Bordeaux, I2M, UMR 5295, 16 Avenue Pey-Berland, 33600 Pessac, France 1 2 Abstract: Lascaux Cave in France contains valuable Palaeolithic paintings. The importance of the paintings, one of the finest examples of European rock art paintings, was recognized shortly after their discovery in 1940. In the 60’s of the past century the cave received a huge number of visitors and suffered a microbial crisis due to the impact of massive tourism and the previous adaptation works carried out to facilitate visits. In 1963, the cave was closed due to the damage produced by visitors’ breath, lighting and algal growth on the paintings. In 2001, an outbreak of the fungus Fusarium solani covered the walls and sediments. Later, black stains, produced by the growth of the fungus Ochroconis lascauxensis, appeared on the walls. In 2006, the extensive black stains constituted the third major microbial crisis. In an attempt to know the dispersion of microorganisms inside the cave, aerobiological and microclimate studies were carried out in two different seasons, when a climate system for preventing condensation of water vapor on the walls was active (September 2010) or inactive (February 2010). The data showed that in September the convection currents created by the climate system evacuated the airborne microorganisms whereas in February they remained in suspension which explained the high concentrations of bacteria and fungi found in the air. This double aerobiological and microclimate study in Lascaux Cave can help to understand the dispersion of microorganisms and to adopt measures for a correct cave management. Keywords: aerobiology; bacteria; fungi; caves; Palaeolithic paintings; culture-dependent methods; climatic simulations Received 3 December 2013; Revised 10 April 2014; Accepted 24 May 2014 Citation: Martin-Sanchez P.M., Jurado V., Porca E., Bastian F., Lacanette D., Alabouvette C. and Saiz-Jimenez C., 2014. Airborne microorganisms in Lascaux Cave (France). International Journal of Speleology, 43 (3), 295-303. Tampa, FL (USA), ISSN 0392-6672 http://dx.doi.org/10.5038/1827-806X.43.3.6 INTRODUCTION Lascaux Cave and other sites in the Vézère Valley, France, were included in the UNESCO World Heritage List in 1979. This cave, discovered in 1940, contains valuable Palaeolithic paintings. The cave was open to the public in 1948 and attracted a large audience which reached 100,000 visitors/year in 1962. This seriously disturbed the cave microclimate and had a strong impact on the ecosystem (Bastian et al., 2010). Unfortunately, at that time, there was no scientific knowledge of cave conservation problems and the huge number of visitors resulted in fatal management errors that marked the future of the cave. Currently, Lascaux Cave is an endangered cavity that was studied from a microbiological point of view since the 60’s of the past century, but unfortunately very few data were published before 2009 (e.g. Lefèvre & Laporte, 1969; Lefèvre, 1974; Dupont et al., * 2007). In the last 50 years the cave suffered several microbiological crises (outbreak of microorganisms threatening the paintings) due to the invasion of the alga Bracteacoccus minor in 1963 (Lefèvre, 1974) and the fungus Fusarium solani in 2001 (Dupont et al., 2007). At present, the paintings are threatened by black stains produced by the fungus Ochroconis lascauxensis (Martin-Sanchez et al., 2012a) as documented in the pictures published by Bastian et al. (2010) and Jurado Lobo et al. (2010). In the last few years several reports on the microbiology of this cave were published, which contributed to understand the complex processes of microbial colonization and biodeterioration of the cave and its paintings (Bastian et al., 2009, 2010; MartinSanchez et al., 2012 a,b; Saiz-Jimenez et al., 2012). One of the aspects more neglected in cave research is the study of cave aerobiology, although this issue is of great interest for a correct cave management. 296 Martin-Sanchez et al. A historical overview revealed that until the 1970’s, a monitoring of the microbiological contamination of Lascaux Cave was carried out by the Institute Pasteur (Paris, France). According to our knowledge, data about the aerobiological studies performed on those dates were no published. The task of the sanitary monitoring, including the evaluation of airborne bacteria, fungi and algae was then passed to the Laboratoire de Recherche des Monuments Historiques (LRMH, Champs-sur-Marne, France). For twenty years (from 1970 to 1990), a passive method based on the gravity effect was used to collect airborne microorganisms by LRMH. Open Petri dishes were exposed on the floor for five minutes for bacteria and fungi, or 24 hours for algae. About ten sampling points located inside the cave and in the entrance airlock chamber were checked using this protocol twice a year (Orial et al., 2011). The resulting counts using the passive method varied within very low ranges, from 0 to 15 colony-forming units (cfu) per plate for both bacteria and fungi. The sampling method was changed in 1990 to an active method, based on the suction and pumping of air samples onto culture media. The results published by Orial et al. (2011) were focused on total quantifications of cultivable bacteria and fungi corresponding to the active monitoring carried out until 2009. In summary, they remarked different periods in Lascaux Cave. From 1990 to 2000, the counts remained within low ranges (0-150 cfu/m3 for bacteria and 0-50 cfu/m3 for fungi). In December 2001, when the Fusarium solani outbreak started, the fungal quantifications reached in general low-medium levels (50-250 cfu/m3). From 2002 to 2003, the bacterial and fungal counts varied between very low and medium ranges (0-250 cfu/m3). In 2004, the levels of bacteria and fungi were particularly increased reaching a high level (250-500 cfu/m3) in December, and even surpassing it in some halls. This increase was directly related to the frequent human activities performed in those dates. Since then, from 2006 to 2009, the microbial contamination fell notably and returned to lower levels. Very little information was provided on the identification of microorganisms detected in this study, only the most abundant genera: Fusarium, Cladosporium, Gliomastix, Penicillium and (...truncated)