Growth of cyanobacteria (blue-green algae) on urban buildings

Abstract

Black and brown patches, indicating the growth of certain cyanobacteria, are very common on building surfaces in the tropics. The patches are mainly comprised of colonial species of cyanobacteria such as Gloecapsa, Gloeothece, Aphanocapsa, and Choococcus, and filamentous species like Scytonema and Tolypothrix. The colonial forms were primary colonizers. Water relation studies revealed that colonial and filamentous crusts which absorbed nearly 165% and 191% water at 0 bar osmotic water potential, lost up to 60, 70 and 80% of the absorbed water on exposure to the atmosphere of −28, −46 and −210 bar in time periods of about 10, 9 and 7 hours, respectively, at 32 °C. The colonial and filamentous crusts, growing as well as dried over conc. H 2SO 4, were separately subjected to various water potentials—matric, osmotic and osmotic-oversaturated — at 0 bar and temperatures to study their viability and growth in terms of 14CO 2 fixation. It was found that 0 bar osmotic water potential and 30 °C temperature were optimum for 14CO 2 fixation. When the dried algae exposed to higher temperatures (55–110 °C) were grown, they did not show much variation in 14CO 2 fixation compared to the unexposed algae.