Light quality rather than oxidative stress impacts fucoxanthin content in <i>Coscinodiscus radiatus</i> and <i>Cylindrotheca</i> sp.

ABSTRACT We investigated the impact of light intensity, light quality, and temperature on growth rate, fucoxanthin (Fx), chlorophyll a and c (Chl a and c), and total carotenoid (Car) contents of the two marine diatoms Coscinodiscus radiatus and Cylindrotheca sp. Additionally, we analysed antioxidant enzyme activities and lipid peroxidation to determine if oxidative stress was associated with Fx accumulation. Cylindrotheca sp. showed the highest Fx concentrations (3.52 ‐ 3.78 mg g −1 DW) under low temperature (12 °C) and low light intensities (12.5 and 25 μmol m −2 s −1 ) in the cool white and lumoflor fluorescent light (FL) treatments. Fx concentrations in Coscinodiscus radiatus were generally lower and the maximum was found at 18 °C and a light intensity of 12.5 μmol m −2 s −1 (0.97 and 1.10 mg g‐1 DW, respectively, for cool white and lumoflor FL). Blue light enriched LEDs significantly increased Fx production in Cylindrotheca sp. making LED lights a promising choice for indoor mass cultivation of algae. No relationship between oxidative stress and Fx production was found in C. radiatus , while a negative relationship was observed in Cylindrotheca sp. suggesting that oxidative stress induction strategies are not generally suitable for enhancing Fx production in all marine diatom species.