Abstract
This study explores how light quality and nutrient availability affect the colouration, composition and physiology of Chondracanthus teedei var. lusitanicus , a red alga with potential applications in the food industry and European aquaculture. Seaweeds were exposed to four different light qualities (blue, green, amber, and red) and two nutrient conditions (nitrogen and phosphate (NP) enrichment, and phosphate (P) enrichment). Growth rates, pigment composition, protein content, photosynthetic performance and carbon and nitrogen content were determined. Results indicated that nitrogen availability was the most significant factor determining colouration and biological performance over the short-term (11 days). Nitrogen deficiency led to depigmentation and impaired photosynthetic performance. Light quality also influenced colouration and physiology, but the effects were slower and less pronounced. The interaction between nitrogen availability and light quality resulted in three distinct morphotypes: bluish-green under all NP enrichment treatments, dark green under blue light and P enrichment, and pale green under green, amber, and red lights with P enrichment. Blue light combined with NP enrichment increased chlorophyll a , carotenoids, and biliproteins (phycoerythrin and phycocyanin) content whereas red light yielded the highest growth rates under both nutrient conditions. This study emphasizes the importance of environmental factors in macroalgal cultivation and provides insights for developing short-term cultivation protocols to produce high-quality, visually appealing seaweed biomass for gastronomic use.