Ecophysiological modeling of the impact of light intensity and quality on microalgal growth in outdoor high-density open ponds

Sammendrag

Light is a critical factor governing microalgal growth, with both intensity (photosynthetically active radiation, PAR) and spectral composition (wavelength distribution) exerting significant influence. In high-density open raceway ponds, light attenuation creates pronounced vertical gradients in both PAR and spectral quality, though the specific effects of spectral composition on phytoplankton growth remain insufficiently characterized. This investigation examined the combined impacts of light intensity, spectral quality, and temperature on Dunaliella salina cultivated in greenhouse-based raceway ponds under natural irradiance. Outdoor experiments spanned two seasonal conditions (winter and summer), with cultures exposed to four spectral treatments: raceways equipped with neutral, red, and green filters, along with an unfiltered control system. Experimental data were used to parameterize a growth model integrating light intensity, spectral quality, and temperature dependencies. The model reproduced biomass dynamics under all spectral conditions and seasons. Notably, when normalized for PAR and initial biomass, green light promoted superior biomass conversion efficiency—attributed to its enhanced vertical penetration in high-light conditions. These findings highlight the potential of spectral optimization in raceway cultivation systems. The model provides a valuable tool for selecting semi-transparent photovoltaic filters or colored panels to simultaneously enhance microalgal productivity and harness unused wavelengths for energy generation.