Effects of Nitrogen and Micronutrients on Spirulina platensis Physiology

Spirulina platensis, a filamentous cyanobacterium, is extensively cultivated for its nutritional value and bioactive compounds. Environmental stressors significantly affect its growth and biochemical composition. This study examines the impact of nitrogen (NaNO₃) and micronutrient (MgSO₄, CaCl₂) stress on biomass production, specific growth rate, and chlorophyll a content in S. platensis. Cultures were grown in modified Zarrouk’s medium with fivefold increased nutrient concentrations. Growth was monitored spectrophotometrically at 565 nm (biomass), 680 nm (chlorophyll-a), and 750 nm (growth rate). Results revealed that NaNO₃ stress reduced growth and pigment accumulation, while MgSO₄ and CaCl₂ stress enhanced both. The highest biomass (0.8851 g/L) was recorded under CaCl₂ stress, and the lowest (0.2754 g/L) under NaNO₃ stress. These findings highlight the potential of micronutrient enrichment in optimizing Spirulina cultivation.