The effect of light intensity, spectrum, and photoperiod on the physiological performance of Asparagopsis taxiformis tetrasporophytes

Abstract

Over the last several years there has been increased interest in large scale cultivation of the red seaweed Asparagopsis taxiformis due to its ability to reduce methane emissions in ruminant animals. However, research focused on developing strategies to optimize culture conditions for this alga is still relatively scarce. Both light quality and quantity are widely known to differentially influence any alga's photosynthetic rates, metabolic budgets and ultimately biomass and bio-active compound production. Optimization of cultivation conditions for algae requires the understanding and fine-tuning of light parameters including Photon Flux Density (PFD), light spectrum, and photoperiod, as well as culture density which largely governs light quantity (PFD) and quality (spectrum) within the culture. Here we explore the effects of light intensity, spectral light distribution, and day length on the physiological performance of the tetrasporophyte stage of A. taxiformis in culture using a series of experiments. The results were used to characterize the optimal light and biomass density range for cultivation, and a model was developed to optimize the light path in a cultivation vessel. Spectral light optimization revealed a significant reduction in cyanobacterial contamination for cultures illuminated with blue LED light. Artificially extending light duration longer than 12 h per day did not improve algal growth. The insights gained from these experimental results may be used to inform the design of tank-based A. taxiformis cultivation systems to support high yield and stable production of this emerging commercial crop.