Factors affecting the weathering and colonization of monuments by phototrophic microorganisms

Phototrophic microorganisms are common inhabitants of monuments. This paper reviews different aspects of their culture, ecology and deterioration mechanisms. Opportunistic species of cyanobacteria and chlorophytes, present in soils and in the air, are commonly found on the surfaces of monuments. Their growth represents a significant input of organic matter to the stone, as estimated through chlorophyll a quantification. Monuments provide unusual niches for the growth of algal communities, as in the case of black sulfated crusts, or endolithic and hypogeal niches, where more specific processes and/or communities occur.