The Effect of Light Intensity and Photoperiod on Marine Diatom Melosira sp

Abstract

Diatoms are a major group of microalgae, found in the water environment. Melosira sp. is a diatom known for its potential as an alternative source for food, fuel, and supplements. Due to its big size, high silica, and pigment content, the opportunity to utilize this species is widely open. Many factors are known to contribute to the growth of Melosira among them are light and photoperiod, which are still understudied. This study aims to investigate the effect of light intensities and photoperiod on Melosira growth and the impact of photoperiod on pigment production For this purpose, Melosira samples were inoculated with an air supply at pH 7, 24°C, two different light intensities (2230 lx and 4310 lx), and a photoperiod of 12h:12h. Based on the best light intensities for biomass growth, another experiment was set up using photoperiod treatment of 12h:12h for the first 12 days of the experiment. Then the photoperiod switched to 24h:0h on the last 2 days of inoculation. The cell growth, silicate, and phosphate uptake were 76%, 47%, and 40% higher at 2230 lx than 4310 lx of light intensity. Furthermore, chlorophyll-a was increased by 20%, and carotenoid concentration was increased by 41% after the photoperiod switched to 24h: 0h cycle. It can be concluded that the light intensity of 2230 lx was preferable for Melosira's growth, which can be recognized from the higher nutrient uptake. The longer photoperiod could trigger the higher chlorophyll-a and carotenoid concentration in the Melosira sp.