Diversity and seasonal variation of viable algal particles in the atmosphere of a subtropical city in India.

To characterize the airborne algal diversity in a populous subtropical urban environment, sampling was done at a height of 2.5m, the normal human breathing zone. Results indicated that airborne algae are the permanent constituent of Varanasi city atmosphere. The nature, composition, and relative ratio of constituting groups differed among sampling sites. Cyanobacteria, possibly due to their broad ecological distribution, dominate the fluctuating climates of subtropical regions such as Varanasi. The majority of the airborne algae were of local origin, indicating short-distance transport of the algae. Soilborne algae constituted the bulk of aeroalgal flora. This might be due to their ability to withstand the dehydrating effect of the atmosphere. Composition of the aeroalgal community also exhibited seasonal variation along with the change in climatic condition of the area. Thus, the physiological ability of an algal group to tolerate different types of abiotic stresses and the climatic conditions of the area appeared to be the two major factors responsible for regulating the structure of the aeroalgal community in the air.