Growth and pigment content of Gracilaria tikvahiae McLachlan underfluorescent and LED lighting

Light emitting diode (LED) technology has significant potential advantages over other light sources in algal aquaculture. This study investigated LEDs as light sources for the culture of Gracilaria tikvahiae. We cultured a wild-type and a green mutant strain of G. tikvahiae, comparing growth rate and tissue chlorophyll a, total carotenoids, and phycobiliprotein concentrations under high output cool white fluorescent, pure primary color LED, and mixed LED lighting. Under monochromatic light, the growth rates under high output cool white fluorescent lighting were significantly higher than rates under pure LED light (all three colors for wild strain and green and blue for green mutant). However, when pure color LED lighting was mixed (50%/50%), the red + green (wild-type strain and green mutant) and the green + blue LED combinations (wild-type only) showed growth rates similar to those under high output cool white fluorescent lighting. In the trichromatic experiment, growth of the wild-type strain under mixed three-color (40%/40%/20%) LED light was indistinguishable from those of the fluorescent control lighting. Chlorophyll a and carotenoid concentrations of Gracilaria grown in the dichromatic light experiment were 55% and 74% higher, respectively, under red + blue LED lighting than under the other light treatments. The wild-type strain of G. tikvahiae possessed significantly greater concentrations of chlorophyll a, and phycoerythrin than did the green mutant, while green mutant thalli had higher phycocyanin levels. With rising LED efficiency and energy savings, LEDs will be an increasingly better choice for indoor seaweed cultivation, especially if control of pigment production and morphogenesis by selective use of particular wavelengths is desirable.