Practice question

Brown algae Phaeophyceae within stramenopiles display olive-brown hue due to dominance of accessory light harvesting carotenoid fucoxanthin over chlorophyll a, chlorophyll c1 and c2, and beta-carotene pigments. Fucoxanthin bound to fucoxanthin-chlorophyll a/c protein complexes absorbs blue-green light 450 to 540 nanometers abundant at moderate depths, efficiently transferring excitation to chlorophyll a for photosynthesis. Pigment composition masks green chlorophyll, conferring characteristic coloration to kelps, rockweeds, and Sargassum. Unlike phycoerythrin providing red coloration in red algae and phycocyanin blue in cyanobacteria, fucoxanthin pigment defines brown algal ecological niche.