Fig. (2) Fluorescence imaging of the dynamic evolution of Chlorella vulgaris inoculated on control (untreated stones) and treated stones. Samples were 30 min dark adapted and submitted to saturation pulse. A photo of the PSII efficiency (Fv/Fm) and of the maximal fluorescence Fm were captured every test week. The false colour code ranges from black (0.000) to magenta (1.000).