<![CDATA[Intensitas cahaya merupakan faktor utama yang memengaruhi fotosintesis, pertumbuhan, dan biosintesis pigmen pada mikroalga. Spirulina platensis memiliki kemampuan adaptasi fisiologis yang tinggi terhadap variasi cahaya, namun informasi mengenai respons pertumbuhan dan dinamika klorofil-a dalam satuan lux masih terbatas. Penelitian ini bertujuan menganalisis pengaruh intensitas cahaya terhadap kepadatan sel, laju pertumbuhan, dan kandungan klorofil-a S. platensis. Penelitian dilakukan secara eksperimental menggunakan rancangan acak lengkap dengan tiga perlakuan intensitas cahaya (500, 1029, dan 2000 lux) dan tiga ulangan. Kultivasi berlangsung selama tujuh hari dengan kepadatan awal 8,910 sel/mL menggunakan media Walne. Kepadatan sel diamati setiap hari, laju pertumbuhan dihitung pada fase eksponensial, dan klorofil-a dianalisis secara spektrofotometri. Hasil menunjukkan bahwa perlakuan 2000 lux menghasilkan kepadatan sel tertinggi (29,232 ± 8,907 sel/mL), laju pertumbuhan tertinggi (0,23 ± 0,05 hari⁻¹), serta kandungan klorofil-a tertinggi (0,333 ± 0,0085 µg/L). Uji ANOVA (α = 0,05) menunjukkan bahwa intensitas cahaya berpengaruh signifikan terhadap kandungan klorofil-a, dengan perlakuan 2000 lux berbeda nyata dibandingkan perlakuan lainnya. Analisis regresi menunjukkan hubungan positif yang kuat antara klorofil-a dan laju pertumbuhan (R² = 0,7991). Pola ini mencerminkan mekanisme fotoaklimatisasi, di mana peningkatan klorofil-a mendukung efisiensi fotosintesis dan pertumbuhan S. platensis. Light intensity is a major factor affecting photosynthesis, growth, and pigment biosynthesis in microalgae. Spirulina platensis exhibits high physiological adaptability to light variation; however, information on growth responses and chlorophyll-a dynamics under different light intensities expressed in lux remains limited. This study aimed to analyze the effects of light intensity on cell density, growth rate, and chlorophyll-a content of S. platensis. The experiment was conducted using a completely randomized design with three light intensity treatments (500, 1029, and 2000 lux), each with three replicates. Cultivation was performed for seven days with an initial density of 8,910 cells/mL using Walne medium. Cell density was observed daily, growth rate was calculated during the exponential phase, and chlorophyll-a content was determined spectrophotometrically. The results showed that 2000 lux produced the highest cell density (29,232 ± 8,907 cells/mL), growth rate (0.23 ± 0.05 day⁻¹), and chlorophyll-a content (0.333 ± 0.0085 µg/L). One-way ANOVA (α = 0.05) indicated that light intensity significantly affected chlorophyll-a content, with the 2000 lux treatment being significantly different from the other treatments. Regression analysis revealed a strong positive relationship between chlorophyll-a content and specific growth rate (R² = 0.7991). These results reflect photoacclimation mechanisms, in which increased chlorophyll-a enhances photosynthetic efficiency and growth of S. platensis. ]]>
