Background and Objectives: Nostoc species have gained much interest as a natural source of many secondary metabolites that have exhibited pharmacological properties. They synthesize UV-protective substances such as mycosporine-like amino acids (MAAs) or scytonemin to minimize the deleterious effects caused by UV radiation. In this research the effects of UVB radiation on increasing amount of UV-protective substances (scytonemin, OS-MAAS), and growth parameters such as photosynthetic pigments, protein and sugar content were studied in cyanobacteria Nostoc linckia.

Methods: For this purpose, 14-day algal cultures were treated with UVB rays for 1, 2 and 3 hours per day for 5 days. After treatment, the growth rate according to fresh weight measurement and other biochemical parameters according to colorimetric methods were assayed. Data were analyzed by one-way analysis of variance, and the significance of the differences was estimated by Duncan’s multiple comparison tests.

Findings: UVB treatment resulted in lower fresh weight of Nostoc algae. Algae exposure to 3 hours UVB, showed an increase in OS-MAAS content. The amount of scytonemin increased up to 3 times in 3 hours UVB treatment. The algae treated with UVB had more chlorophyll a and total carotenoid content but phycobiliproteins content reduced in this treatment. Total protein and total sugars were not affected by UVB treatment.

Conclusion: The results showed that this UV treatment method, in addition to significantly enhancing the anti UV compounds of the algae, would not reduce the biomass.