Chlorophyll a fluorescence as a practical tool for checking the effects of biocide treatments on endolithic lichens

The efficacy of three biocides (Benzalkonium chloride, Koretrel, and Rocima 110) on two endolithic lichens (Acrocordia conoidea and Bagliettoa marmorea) was monitored in the laboratory and in the field with portable pulse-amplitude-modulated (PAM) equipment. For comparison, epifluorescence microscope observations were carried out in the laboratory on cross-sections of treated and untreated thalli. The PAM equipment revealed excellent sensitivity for quantifying variations that could not be appreciated in epifluorescence. The two lichens showed a differential resistance to the biocides, probably related to the different photobionts and absorption of the active principle. The contribution of ChlaF techniques to the field of stone conservation is discussed.