Lampenflora growth-control: the challenge of the show caves

Show caves are subjected to tourist adaptations, often with negative consequences on the ecological equilibria of the system. Among the worst problems, photosynthetic biofilms, called “lampenflora”, can develop on surfaces due to the artificial lighting system, covering with green patinas every lit rocks, included speleothems, such as the still few known vermiculations. They implement biodeteriorations processes on surfaces, damaging them irreversibly. The aim of this study was to investigate the efficacy of lampenflora growth-control strategies, carried out monthly using chemical (15% hydrogen peroxide2 or commercial bleach) and physical (UV-C) remedies, on surfaces with and without vermiculations. The tests were performed in the tourist trail of the Pertosa-Auletta Cave (southern Italy), lit and frequented by human beings, analyzing, before and after the treatments, the chlorophyll fluorescences (MINI-PAM, Walz), an in situ non-destructive method representing a proxy of the biofilms photosynthetic activities. The results highlighted an evident reduction of the lampenflora photosynthetic activity already after the 1st treatment. Before every actions, the dark-adapted surfaces, with and without vermiculations, displayed Fv/Fm values between 0.766-0.713 and 0.710-0.663, respectively. After chemical treatments, using H2O2 or commercial bleach, the maximal PSII photochemical efficiency was close to 0, showing an almost complete reduction of the photosynthetic activity. Such values have been maintained until the 2nd treatment, in pre- and post phase. After three months without treatments due to the pandemic lockdown closure of the show cave, there was a slight recovery of lampenflora on the surfaces treated with H2O2, immediately stopped after the 3rd treatment. No effect occurred on the surfaces treated with UV-C, probably in relation to the low frequency of treatments (one night) in a month.