Biofilm biodiversity in French and Swiss show caves using the metabarcoding approach: First data Stéphane Pfendler a , Battle Karimi b , Pierre-Alain Maron b , Lisa Ciadamidaro a , Benoît Valot a , Faisl Bousta c , Laurence Alaoui-Sosse a , Badr Alaoui-Sosse a , Lotfi Aleya a, ⁎ a Laboratoire Chrono-Environnement, UMR CNRS 6249, Université de Bourgogne Franche-Comté, Besançon, France b Institut National de Recherche Agronomique (INRA), UMR1347 Agroécologie, BP 86510, F-21000 Dijon, France c Laboratoire de Recherche des Monuments Historiques (LRMH), CRC-USR 3224, Champs-Sur-Marne, France HIGHLIGHTS • Bacteria, cyanobacteria, algae, diatoms, fungi and mosses were sequenced. • Bacteria were the most abundant organ- isms present in the biofilms. • 23S primer provided an overview of the mosses present in biofilms. • This study showed the low efficiency of chemical treatment over time. GRAPHICAL ABSTRACT abstract article info Article history: Received 1 September 2017 Received in revised form 6 October 2017 Accepted 7 October 2017 Available online xxxx Editor: D. Barcelo In recent decades, show caves have begun to suffer from microorganism proliferation due to artificial lighting in- stallations for touristic activity. In addition to the aesthetic problem, light encourages microorganisms that are responsible for physical and chemical degradation of limestone walls, speleothems and prehistoric paintings of cultural value. Microorganisms have previously been described by microscopy or culture-dependent methods, but data provided by new generation sequencing are rare. The authors identified, for the first time, microorgan- isms proliferating in one Swiss and in four French show caves using three different primers. The results showed that both photosynthetic and non-photosynthetic bacteria were the dominant taxa present in biofilms. Microalgae were heavily represented by the Trebouxiophyceae, Eustigmatophyceae and Chlorophyceae groups. Twelve diatoms were also recorded, with dominance of Syntrichia sp. (96.1%). Fungi were predominantly repre- sented by Ascomycota, Zygomycota and Basidiomycota, fully half of the sampled biofilms where Fungi were de- tected. Comparing microbial communities from bleach-treated caves to those in untreated caves showed no significant difference except for a low-level change in the abundance of certain taxa. These findings provided by Illumina sequencing reveal a complex community structure in the 5 caves based on the assembly of bacteria, cyanobacteria, algae, diatoms, fungi and mosses. © 2017 Elsevier B.V. All rights reserved. Keywords: Metabarcoding Caves Conservation Biodiversity Microorganism communities Science of the Total Environment 615 (2018) 1207–1217 ⁎ Corresponding author. E-mail address: lotfi.aleya@univ-fcomte.fr (L. Aleya). https://doi.org/10.1016/j.scitotenv.2017.10.054 0048-9697/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv