Diversity and distribution of heterocystous cyanobacteria across solar radiation gradient in terrestrial habitats of Iran

Cyanobacteria are important part of microflora in terrestrial ecosystems. Due to the presence of protective mechanisms in these microorganisms, they have potential to tolerate abnormal ecological conditions especially in arid and semi-arid habitats. In the present study, the diversity, distribution and community’s structure of the heterocystous cyanobacteria isolated from natural habitats of Iran with different solar radiation gradient were investigated. In total, 41 heterocystous morphospecies were isolated from soils of 21 studied sites. The isolated taxa were belonged to eight genera including Nostoc (54.68%) followed by the Calothrix (13.63%), Cylindrospermum (9.76%), Anabaena (7.32%), Trichormus (7.32%), Wollea (2.43%), Nodularia (2.43%), and Hapalosiphon (2.43%), respectively. According to the results, ecological factors such as solar radiation, relative humidity, and soil salinity can affect the diversity and distribution of these cyanobacteria in terrestrial ecosystems. The results also showed that, some taxa were dominant in stations with high radiation levels. Among the identified taxa, Nostoc was found to be the dominant genus at all stations, especially in sites with higher solar radiation levels. In addition, the presence of the brown Nostoc species in arid areas confirming their resistance due to their high amount of carotenoids content and other protective mechanisms that protect them from high light intensity.