Growth and photosynthetic characteristics of Gracilaria lemaneiformis (Rhodophyta) and Ulva lactuca (Chlorophyta) cultured under fluorescent light and different LED light

The effects of fluorescent light and different light-emitting diodes (LEDs) with white, red, green, and blue light on two macroalgal species, Gracilaria lemaneiformis (Rhodophyta) and Ulva lactuca (Chlorophyta), have been investigated via the measurements of growth rates, photosynthesis, and biochemical contents of pigments (i.e., chlorophyll a, carotenoids, and phycobilin) and soluble protein. In the two species, white LEDs showed similar effects to fluorescent lamps on the relative growth rates (RGRs) and gross maximum photosynthetic rate (Pmax). In addition, green LEDs contributed to the highest RGRs and Pmax in G. lemaneiformis. Interestingly, when compared with fluorescent lamps, green LEDs resulted in a significantly higher Pmax in U. lactuca. Furthermore, blue LEDs contributed to the highest RGRs of U. lactuca, while the red LEDs led to the lowest RGRs of U. lactuca. Overall, our study suggests that LEDs are alternative monochromatic light sources to fluorescent lamps in G. lemaneiformis and U. lactuca cultivation.