Abstract
The combined effects of UV-A or UV-B radiation and red LED light on subaerial biofilm formation were studied. Biofilms were generated using cultures isolated from natural phototrophic biofilms growing on the granite facades of the Palace of Xelmírez and the Monastery of San Martiño Pinario, both historic buildings in Santiago de Compostela (NW Spain). Red LED and UV-A or UV-B radiation were tested separately and together in the same experiment, along with white LED (positive control) and no LED or UV lights (i.e. darkness, negative control). The initial target biofilms had different ratios of green algae: cyanobacteria [cells mL−1] of 100:1 (Xelmírez) and 5:1 (Pinario). Relative to the other treatments, the combination of UV-A and red LED significantly enhanced growth of the biofilm mainly comprising algae. Relative to the negative control, proliferation of Isocystis sp. and Stichococcus bacillaris also increased (by respectively 10% and 36% in Xelmírez and by 2% and 44% in Pinario), while the occurrence of Bracteacoccus minor decreased (by 47% in Xelmírez and 46% in Pinario). UV-B plus red LED also impeded the proliferation of Bracteacoccus minor (by 7% in Xelmírez and 14% in Pinario), but conversely resulted in poor biofilm growth.
Published Version
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