Photosynthetic pigments and photoprotective metabolites of Colombian pacific marine macroalgae in response to contrasting ultraviolet-index periods

Abstract

Tropical macroalgae have developed specific defense mechanisms, synthesizing photoprotective molecules to cope with solar radiations, especially ultraviolet radiation, which hits them intensely. Despite the vast Colombian marine biodiversity, not all the country's coastlines have received the same attention, like the Pacific coast. In this study, we assessed photosynthetic pigments (chlorophylls and carotenoids) and photoprotective compounds (mycosporine-like amino acids - MAAs) in seaweeds from the Colombian Pacific coast. We collected seven species of seaweeds, namely Boodleopsis verticillata, Bostrychia calliptera, B. radicans, B. cf. scorpioides; Catenella impudica, Cladophora graminea and Rhizoclonium riparium, easily found in supralittoral and mangrove ecosystems, at low tide, in contrasting periods of high and low UV index over the year of 2021. The sampling area encompassed a latitudinal gradient (3° S to 6° S) along the Colombian Pacific coast, changing the pattern of the chlorophyll-a and total carotenoid content in different species collected in contrasting UV-index periods. MAAs were quantified using standards (shinorine, porphyra-334, and palythine). This study corroborates the hypothesis that tropical species produce higher concentrations of MAAs in response to UV radiation, with significant differences in the high UV-index period. The highest MAA content (5.68 mg.g−1 DW) was reported in Bostrychia calliptera during the high UV-index period. Ceramiales and Cladophorales species represented a photoprotective potential with at least six different MAAs. Shinorine, palythine and porphyra-334 were quantified; and mycosporine-methylamine-serine and aplysiapalythine C were putatively identified by LC-MS/MS dereplication, this, therefore representing a pioneer study on the chemical composition of Colombian Pacific marine macroalgae.