Dynamic structural colour increases photosynthetic performance in the alga Ericaria selaginoides

Abstract

Structural colour occurs when nanoscale structures interfere with incident light transmission and reflect particular wavelengths. The brown alga Ericaria selaginoides (Fucales, Phaeophyceae) has an opalescent photonic crystal anatomy that creates the blue colour of this seaweed but which responds to light, leading to speculation that the crystals have a photosynthetic role by modifying light transmission. Here, we characterize the colour response of E. selaginoides using time-lapse photography to capture responses to light treatments of different timing, duration, intensity and spectrum. The amount of light drove the colour response, with the most intense blue found in the dark which reduced rapidly in strong light and was not spectrum dependent. Chlorophyll a fluorometry showed that the maximum quantum efficiency of photosynthesis coincided with strong blue colouration but was reduced over two to three hours of illumination. This supports opalescent photonic crystals having a photosynthetic role by regulating light transmission to chloroplasts. Studies such as this could be used to improve solar cell efficiency and increase crop yield through the use of bio-inspired self-tuning mechanisms to optimize light transmission.