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Lascaux cave (France)

UVC irradiation as tool to eradicate algae in caves. BORDERIE F., ALAOUI-SEHMER L., RAOUF N. , BOUSTA F., ORIAL G., RIEFFEL D. & ALAOUI-SOSSE B.*. * Department of Chrono-Environment, UMR UFC/CNRS 6249 USC INRA University of Franche-Comte, 2 Place Leclerc, F-25030 Besançon cede, FRANCE

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Lascaux cave (France)

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  1. UVC irradiation as tool to eradicate algae in caves BORDERIE F., ALAOUI-SEHMER L., RAOUF N., BOUSTA F., ORIAL G., RIEFFEL D. & ALAOUI-SOSSE B.* * Department of Chrono-Environment, UMR UFC/CNRS 6249 USC INRA University of Franche-Comte, 2 Place Leclerc, F-25030 Besançon cede, FRANCE Tel. +33 (0)381 665 730, Fax. +33 (0)381 665 797, E-mail : badr.alaoui-sosse@univ-fcomte.fr INTRODUCTION CONCLUSION DISCUSSION RESULTS EXPERIMENTAL Subterranean environments (caves, chasms, ...) constitute a heritage that should be protected. Illumination system installation set up for touristic visits in these particular ecosystems induces development of microorganisms (algae, fungi, ...). Many algae treatments with chemicals compounds have induced ground water polluting effects. Alternative methods have to be developed to remove or control microorganism extension. UV irradiation in order to kill or limit the proliferation of the algae have been investigated. The aim of this study is to determine effects of UV-C irradiation on survival, proliferation and photosynthetic rates of cave harvested algae. Lascaux cave (France) UV-C exposure time : 20mn, 30mn, 60mn and 180mn Survival rate and Photosynthetic activity -concentration of algal cells by centrifugation, -OD measured at 750 nm to estimate the number of cells Algal cultures in liquid medium - UV-C exposure time : 3h, 6h and 9h Macro-photography Colonized area and covering rate Inoculation on limestone blocks Thin and 3h of UV-C Thick and 9h of UV-C 33% 7% 77% 43% Survival rate (%) according to UV-C exposure time Photosynthetic activity , ** indicates significant differences between control and exposed sample at p< 0.01( Kruskal-Wallis test, n=3) Middle and 6h of UV-C UV-C exposure killed efficiently algae when cultivated in a liquid medium : decrease of survival rate and increase of photosynthesis inhibition 80% 60% The results showed that UV-C exposure decrease the colonized area in all treatments -The disturbance of the photosynthetic pathway has repercussions on the survival ability of the algal cells Algal cells re-inoculated on fresh medium after UV-C exposure were unable to proliferate -The thickness of algal layer is a very important parameter in the optimization of this method, because cells of underlying layers benefit protective effects from overlying layers that filter UV-C irradiations The application of this method is very delicate in caves. Future experiments will investigate the possibility of installation of this method in natural conditions. For the 8th International Symposium on the Conservation of Monuments in the Mediterranean Bassin, May 31 – June 2, 2010 – Patras, Greece Chasm of Padirac
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