Water-depth effects in photosynthetic pigment content of the benthic algae Dictyota dichotoma and Udotea petiolata

Abstract The effect of water depth on the light-harvesting pigments contents in Dictyota dichotoma (Hudson) Lamouroux and Udotea petiolata (Turra) Borgesen was studied. Both species showed higher photosynthetic-pigments contents with increased depth or shade. The ratios of chlorophyll c /chlorophyll a and chlorophyll b / chlrophyll a in D. dichotoma and U. petiolata were lower in light-exposed samples. In D. dichotoma , the ratios of fucoxanthin to chlorophyll a increased with depth or shade; however, it is worth noting that the 0 m (sun) samples showed the highest values. On the other hand, total carotenoids to chlorophyll a ratios in U. petiolata increased with depth.