Seaweed growth is often limited by light. Artificial light supply has been well studied in terrestrial agriculture, however, much less is known about its effect in seaweed aquaculture. In this study, the effects of four artificial light sources (white, red, green, and blue LEDs light) on a brown alga Sargassum fusiforme and a green alga Ulva pertusa were investigated. Seaweed growth, accumulation of photosynthetic pigments (chlorophyll a and carotenoid), and soluble protein were evaluated. White LED light was the optimal supplementary light when cultivating Ulva pertusa and Sargassum fusiforme, because it promoted seaweed growth while maintaining protein production. Meanwhile, red LED was unfavored in the cultivation of S. fusiforme, as it affected the seaweed growth and has a lower residual energy ratio underneath the water. LEDs would be a promising supplementary light source for seaweed cultivation.
