Impact of Cell Size, Light Wavelengths, and Intensities on Growth, Oxygen Production, and Consumption Rates of Chromochloris zofingiensis and Haematococcus lacustris

This study examined the oxygen production, consumption, and morphological characteristics of Chromochloris zofingiensis ( C. zofingiensis ) and Haematococcus lacustris ( H. lacustris ) under autotrophic conditions using blue and red-light at different intensities (20–80 µmol m ⁻² s ⁻¹ ). Both algal species exhibited reduced growth rates as light intensity increased. At 20 µmol m ⁻² s ⁻¹ , C. zofingiensis achieved a higher specific growth rate under blue-light (0.52 d ⁻¹ ) compared to red-light (0.14 d ⁻¹ ), while H. lacustris grew more rapidly under red-light (0.44 d ⁻¹ ) than blue-light (0.12 d ⁻¹ ). Under blue-light, C. zofingiensis demonstrated enhanced oxygen metabolism, with high OPR (10 µmol O ₂ gSS ⁻¹ min ⁻¹ ) and OCR (–7.08 µmol O ₂ gSS ⁻¹ min ⁻¹ ). This performance was associated with its smaller cell size (1.99–8.32 µm) and higher surface area-to-volume ratio (9.6 ± 6.4 ×10 ⁻⁵ m ² m ⁻³ ). In contrast, H. lacustris showed lower oxygen exchange rates with OPR (5.63 µmol O ₂ gSS ⁻¹ min ⁻¹ ) and OCR (–4.85 µmol O ₂ gSS ⁻¹ min ⁻¹ ) consistent with its larger cell size (11.42–26.86 µm) and lower surface area-to-volume ratio (3.4 ± 2.1×10 ⁻¹⁰ m ² m ⁻³ ). Both species exhibited diminished oxygen exchange under red light due to low photon energy and high pH levels. These findings underscore the influence of blue light and cell morphology on microalgae oxygen dynamics.