ABSTRACT
In Postojnska jama, artificial lighting was introduced in the cave as early as 1884 and has become responsible for light eutrophication. The more than 500,000 visitors to the cave and a relatively long lighting period encourage the growth of lampenflora, which deteriorates speleothems and historical inscriptions. Altogether 34 different species of mosses and ferns have been reported among the lampenflora, including eucladioliths. The majority of microscopic phototrophs belong to the Cyanobacteria (59%), followed by Chrysophyta (25%) and Chlorophyta (16%). Since 2011 the procedure for removing lampenflora has been based on hydrogen peroxide (pH 7.0–7.5). Once buffered, hydrogen peroxide becomes unstable, and the solution should be applied approximately 20 minutes after preparation. In Postojnska jama, a complete round of applications consists of three consecutive applications with one week between each application. This procedure is usually repeated twice a year, and is suitable only for treatment of insensitive carbonate surfaces without the presence of cave fauna. In a six-month experiment in Postojnska jama, Chlorella vulgaris, a frequent microscopic lampenflora alga, grew rather undisturbed under LED lamps which emitted cold or warm white light. Suboptimum light quality for photosynthesis leads to increased biosynthesis of photosynthetic pigments. LED lamps did not notably reduce lampenflora biomass in the long term. In show caves, more attention should be given to the lighting regime, positioning of lamps and frequent removal of re-emerging lampenflora around the lamps.
