TITLE:
Effects of Light Wavelength on the Growth Rates of Microcystis and Scenedesmus
AUTHORS:
Alina Poles
KEYWORDS:
Photosynthesis, Light Wavelength, Microcystis, Scenedesmus, Cyanobacteria, Green Algae, Absorbance, Growth
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.17 No.10,
October
26,
2026
ABSTRACT: Light quality can influence the growth of photosynthetic microorganisms because different organisms contain different pigments and light-harvesting systems. This study investigated how white, red, green, and blue LED light affected the growth of Microcystis and Scenedesmus over a three-week experimental period. Microcystis is a photosynthetic cyanobacterium that contains chlorophyll a and phycobiliproteins rather than chlorophyll b, whereas Scenedesmus is a green microalga that primarily uses chlorophylls and carotenoids for light capture. Cultures were exposed to the four light-color treatments, and changes in absorbance were used as an indicator of changes in culture density. The mean growth values were compared using one-way ANOVAs within each species and independent comparisons between species under each light treatment. Neither one-way ANOVA showed a statistically significant effect of light treatment for Microcystis, F(3, 12) = 1.636, p = 0.233, or Scenedesmus, F(3, 12) = 1.561, p = 0.250. The original species comparisons were significant under green light (p = 0.004) and blue light (p = 0.013); however, after Bonferroni correction for four comparisons, only the green-light comparison remained statistically significant because the adjusted significance level was α = 0.0125. An estimated species-by-light interaction based on the reported means, standard deviations, and sample sizes was not statistically significant, F(3, 24) ≈ 1.67, p ≈ 0.20. Therefore, the results do not provide sufficient statistical evidence that the two organisms responded differently to wavelength. The findings suggest that light color may influence growth patterns, but the effects were not statistically significant within either species under the conditions tested.