Microalgae has many benefits for human being. Microalgae is potential source for biodiesel and bioethanol, but the biomass produced from the culture is relatively low. So that, the research has to be done to improve the productivity of the microalgae. Red light and blue light spectrum are known as effective spectrums for the photosynthesis process. Then nitrogen starvation medium is usually performed in order to improve the lipid content. However, nitrogen starvation treatment will decrease microalgae biomass. Therefore, this research aims to study the effect of red and blue light and nitrogen starvation on the growth of Tetraselmis sp. The parameters measured were the cells number, dry weight and chlorophyll a and b. In this study, microalgae Tetraselmis sp. was treated using red and blue light for 7 days. Then, followed by nitrogen starvation treatment with concentration 100%, 50%, and 0% of the f/2 normal medium until day 14. The number of the cells was counted every day for 14 days using a haemocytometer and dry weights were counted at day 0, 1, 5, 7 and 14. Chlorophyll contents were calculated by Jeffrey and Humphrey’s Trichromatic Equations method at absorbance 664 nm, 647 nm, 630 nm, and 750 nm. The results indicated that the red light increased the number of cells to twice as normal, while the blue light increased the number of cells to 1,5 times as normal. Furthermore, the 50% of nitrogen treatment under the red and blue light increased the dry weight to 25% and 60%.

Keywords: Microalgae, Tetraselmis sp., Nitrogen Starvation, Blue and Red light

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