Controlling lampenflora, the green disease of show caves

Artificial lighting in show caves causes the growth of green photosynthetic biofilms, called lampenflora, on rock surfaces. This represents a worrisome ecological problem in caves as these biofilms cause aesthetical, physical and chemical damages on the rock substrates. Finding an efficient eco-friendly control method is now a priority to carry out a sustainable management of cave tourism. In this study we assessed the efficacy of three growth-control methods in Pertosa-Auletta limestone Cave (Italy). Reflectance spectra showed that the lampenflora is able to reflect only the near-infrared, absorbing all the visible light frequencies, likely due to its capability to produce secondary accessory pigments or to the mixotrophic metabolism of some cyanobacterial species. Filamentous organisms, knotted with minerals, promote rock corrosion and the precipitation of carbonate secondary minerals. Treatment of lampenflora with NaClO (commercial bleach) demonstrated its long-term efficacy in disinfection and cleaning of the surfaces, whereas the H2O2 (oxygenated water) revealed a recovery of the biofilms after three months and corrosive effects on the underlying carbonate bedrock. Both the chemical treatments eliminated the photoautotrophs, but not Proteobacteria and Bacteroidetes bacterial phyla, and, among the Eukaryotes, Apicomplexa and Cercozoa. UVC lighting showed no effects on lampenflora with the protocol used in such work.