Photosynthesis, photosynthetic pigments and mycosporine-like amino acids after exposure of the marine red alga Chondrus crispus (Gigartinales, Rhodophyta) to different light qualities

Low light-adapted laboratory-grown thalli of Chondrus crispus were transferred into shallow water and exposed to the natural irradiance prevailing in May-June at Helgoland (German Bight). A set of cut-off filters was used to study the wavelength-dependent response of photosynthesis as well as pigment and mycosporine-like amino acid (MAA) formation. Due to the higher natural irradiance and in some cases additional ultraviolet (UV) radiation, a depression of maximal quantum yield coinciding with a decline in maximal electron transport rate could be observed during the first days of the experiment. Faster recovery of maximal quantum yield and maximal electron transport rate might be related to the increase in lutein and alpha- and beta-carotene concentration. In addition, higher rates of electron transport might be supported by increased chlorophyll a concentration. In parallel, MAA concentration increased resulting in an effective UV sunscreen. Our data suggest that lutein and a- and beta-carotene are involved in the recovery of photochemical capacity, whereas MAAs provide a UV Sunscreen, which may reduce the light available within the algae to long-wavelength UV-A and photosynthetically active radiation.