Summary: | Study on the effects of nitrate concentration and CO₂ on the growth of C.
polykrikoides was conducted in laboratory under controlled conditions. In this
experiment, C. polykrikoides was cultured at four different concentration of nitrate
[4.41 x 10⁻⁴ M, 8.82 x 10⁻⁴ M (control), 9.41 x 10⁻⁴ M, 1.09 x 10⁻³] under two
different conditions which are with and without CO₂ enrichment. The experiments
were conducted under constant light intensity (100 µmolm ⁻²s⁻¹) at 25°C and under
a 12 h light: 12 h dark cycle. Cells were incubated for two weeks and samplings
were done for growth determination at every one day interval. This study shows
that C. polykrikoides reached the maximum density (1200 cells/mL) when grown
at 9.41 x 10⁻⁴ M of nitrate concentration and without CO₂ enrichment. However, in
CO₂ enriched media, the cells density is relatively very low where at the same
concentration of nitrate, cell density was only about 35 cells/mL. These differences
outcomes might due to pH changes. Cell densities of C. polykrikoides were low
when pH extremely decreased (< 6.50) and at higher pH (> 9.00) under CO₂
enriched media. 2-Way ANOVA analysis indicated that the nitrate concentration,
CO₂ and nitrate* CO₂have significant effect (P < 0.05) on the growth of C.
polykrikoides.
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