To cope with the biotic and abiotic stresses experienced within their environment, marine macroalgae have developed certain defence mechanisms including the synthesis of photo-protective molecules against light and particularly harmful UV radiation. The aim of this study was to screen selected red algae, a highly diverse phylogenetic group, for the production of photo-protective molecules. The pigment content and composition (i.e. chlorophyll-a, phycobiliproteins and carotenoids) and the composition of mycosporine-like amino acids (MAAs) were studied in 40 species of red macroalgae collected in Brittany (France), at two distinct periods (i.e. February and July 2017). A high inter-specific variability was demonstrated in terms of pigment content and MAA composition. Twenty-three potential MAAs were detected by HPLC, and six were identified by LC-MS (i.e. shinorine, palythine, asterina-330, porphyra-334, usurijene and palythene). This is the first study to report on the composition of pigments and MAAs in a diverse group of red seaweeds from Brittany, including some species for which the MAA composition has never been studied before. Nevertheless, the results suggested that some species of red algae are more likely to cope with high levels of light radiation since those species such as Bostrychia scorpioides, Porphyra dioica, Gracilaria vermiculophylla and Vertebrata lanosa are living in environments exposed to higher levels of irradiation, and had various MAAs in addition to their photoprotective pigments.Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. Graphical abstractHighlights ► Detection of 23 potential MAAs in 40 Rhodophyta species, including 6 already identified (shinorine, palythine, asterina-330, porphyra-334, usurijene, palythene). ► First report on the MAAs composition for some red seaweeds. ► High variability in MAAs content and composition between the different species, with no link with phylogeny, morphology, position on the shore or sampling site. ► A MAAs extraction method using 70% ethanol being less toxic than conventional methanol, and giving potential valorisable extracts.

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Pelvetia canaliculata (L.) Dcne. et Thur. is a marine brown macroalga within the Fucaceae (Fucales, Phaeophyceae, Ochrophyta) and the only species remaining in the monotypic genus Pelvetia. Abundant on sheltered rocky shores of the North-East Atlantic, Pelvetia forms a distinct horizontal band along the upper fringe in the intertidal, between maritime lichens and Fucus spp. Pelvetia canaliculata is a perennial species, characterized by dichotomously branching thalli 10–15 cm in length, forming narrow channels (“channelled wrack”). Distributed on the extreme upper shore, the species is exposed to atmospheric conditions for prolonged periods between spring high tides; photosynthesis recovers quickly, and fully, after water loss. Effective de-epoxidation of the xanthophyll cycle observed in P. canaliculata constitutes an important photoprotective mechanism in this species which receives high doses of solar radiation during tidal emersion. In comparison with other intertidal brown macroalgae, only few studies have investigated its chemical composition. Pelvetia typically presents high levels of sulphated polysaccharides, alginic acid, and polyphenols, associated with antioxidant and other biological activities. It accumulates high levels of mannitol and volemitol, two sugar alcohols considered to be involved in its tolerance to extended emersion. As a natural cation exchanger, Pelvetia biomass displays high biosorption capacities for toxic metals. Besides its slow growth rate and related small quantities of biomass, low protein content coupled with low degradability, have so far limited its potential for valorization.